Ncma Tek Manual Parts 1-5

NCMA TEK National Concrete Masonry Association an information series from the national authority on concrete masonry technology

ASTM SPECIFICATIONS FOR CONCRETE MASONRY UNITS Keywords: absorption, ASTM specifications, calcium silicate brick, compressive strength, concrete brick, dimensions, face shell and web thickness, gross area, net area, specifications, testing, water absorption

TEK 1-1E Codes & Specs (2007)

2003 and 2006 editions of the International Building Code (IBC) (refs. 1, 2), as well as the most current ASTM edition. Code officials will commonly accept more current editions of ASTM standards than that referenced in the code, as they represent more state-of-the-art requirements for a specific material or system.

INTRODUCTION The most widely-used standards for specifying concrete masonry units in the United States are published by ASTM International. These ASTM standards contain minimum requirements that assure properties necessary for quality performance. These requirements include items such as conformance to specified component materials, compressive strength, permissible variations in dimensions, and finish and appearance criteria. Currently, seven ASTM standards apply to units intended primarily for construction of concrete masonry walls, beams, columns or specialty applications (see Table 1). The letter and first number of an ASTM designation is the fixed designation for that standard. For example, ASTM C 55 is the fixed designation for concrete building brick. The number immediately following indicates the year of last revision (i.e., ASTM C 55-06 is the version of C 55 published in 2006). ASTM standards are required to be updated or reapproved at least every five years. If the standard is reapproved, the reapproval date is placed in parentheses after the last revision date. Because significant changes can be introduced into subsequent editions, the edition referenced by the building code or by a project specification can be an important consideration when determining specific requirements. Also note that it may take several years between publication of a new ASTM standard and its subsequent reference by a building code. For this reason, Table 1 includes the editions referenced in the

LOADBEARING CONCRETE MASONRY UNITS— ASTM C 90 As the most widely-referenced of the ASTM standards for concrete masonry units, ASTM C 90 is under continuous review and revision. The bulk of these revisions are essentially editorial, although two recent major changes are discussed here. In 2006, the minimum face shell thickness requirements were modified for units 10-in. (254-mm) and wider. Prior to ASTM C 90-06 (ref. 2), two minimum face shell thicknesses for these units were listed: • a standard thickness, 13/8 in. for 10-in. units, 11/2 in. for 12-in. and greater (35 mm for 254-mm units and 38 mm for 305-mm and greater), and • a reduced thickness that can be used when the allowable loads in empirical design are correspondingly reduced. Similarly, in the engineered design methods (allowable stress design and strength design), capacity is automatically reduced as the section properties are reduced. With the introduction of ASTM C 90-06, the two sets of face shell thicknesses were replaced with one minimum thickness requirement (see Table 2). In 2000, a prior change was made to ASTM C 90, removing the Type I (moisture-controlled) and Type II (non moisturecontrolled) unit designations which is reflected in the ASTM C 90 editions adopted by the 2003 and 2006 editions of the

Table 1—ASTM Specifications for Concrete Masonry Units ASTM Edition referenced in Type of unit: Designation: the 2003 IBC: the 2006 IBC: Most current edition: Concrete Building Brick C 55 C 55-01a C 55-03 C 55-06 Calcium Silicate Brick C 73 C 73-99a C 73-99a C 73-05 Loadbearing Concrete Masonry Units C 90 C 90-01a C 90-03 C 90-06b Nonloadbearing Concrete Masonry Units C 129 C 129-99aA C 129-01A C 129-06 B Catch Basin and Manhole Units C 139 N/A N/AB C 139-05 Prefaced Concrete Units C 744 C 744-99 C 744-99 C 744-05 Concrete Facing Brick C 1634 N/AB N/AB C 1634-06 A Although not directly referenced in the IBC, C 129 is referenced in Specification for Masonry Structures (refs. 17, 18) B This standard is not referenced in the IBC. 1 TEK 1-1E © 2007 National Concrete Masonry Association (replaces TEK 1-1D)

IBC. The designations were withdrawn because they were difficult to effectively use and enforce, and because of newly developed concrete masonry crack control provisions. The new crack control guidelines are based on anticipated total volume changes, rather than on the specified moisture contents that formed the basis for Type I requirements. Because the Type designations no longer influenced recommended control joint spacing or other crack control strategies, Type designations were removed. Control joint criteria can be found in References 5 and 6. Physical Requirements Physical requirements prescribed by ASTM C 90 include dimensional tolerances, minimum face shell and web thicknesses for hollow units, minimum strength and maximum absorption requirements, and maximum linear shrinkage. Overall unit dimensions (width, height and length) can vary by no more than ± 1/8 in. (3.2 mm) from the standard specified dimension. Exceptions are faces of split-face units and faces of slump units which are intended to provide a random surface texture. In these cases, consult local suppliers to determine achievable tolerances. Molded features such as ribs, scores, hex-shapes and patterns must be within ± 1/16 in. (1.6 mm) of the specified standard dimension and within ± 1/16 in. (1.6 mm) of the specified placement on the mold. For dry-stack masonry units, the physical tolerances are typically limited to ± 1/16 in. (1.6 mm), which precludes the need for mortaring, grinding of face shell surfaces or shimming to even out courses during construction (ref. 7). Minimum face shell and web thicknesses are those deemed necessary to obtain satisfactory structural and nonstructural performance. Note that although there are some unique face shell thickness requirements for split-faced units (see Table 2 Table 2—ASTM C 90 Minimum Thickness of Face Shells and Webs for Hollow Units (ref. 3) Web thickness Nominal Face shell Equivalent width thicknessB, C, web thickness, of units, minimum, WebsB, C, D in./linear ftE in. (mm) in. (mm) in. (mm) (mm/linear m) 3 3 3 (76.2) & 4 (102) /4 (19) /4 (19) 15/8 (136) 6 (152) 1 (25)D 1 (25) 21/4 (188) 1 D 8 (203) 1 /4 (32) 1 (25) 21/4 (188) 1 1 10 (254) and greater 1 /4 (32) 1 /8 (29) 21/2 (209) A Average of measurements on a minimum of 3 units when measured as described in Test Methods C 140. B When this standard is used for units having split surfaces, a maximum of 10% of the split surface is permitted to have thickness less than those shown, but not less than 3/4 in. (19.1 mm). When the units are to be solid grouted, the 10% limit does not apply and Footnote C establishes a thickness requirement for the entire face shell. C When the units are to be solid grouted, minimum face shell and web thickness shall be not less than 5/8 in. (16 mm). D The minimum web thickness for units with webs closer than 1 in. (25.4 mm) apart shall be 3/4 in. (19.1 mm). E Equivalent web thickness does not apply to the portion of the unit to be filled with grout. The length of that portion shall be deducted from the overall length of the unit for the calculation of the equivalent web thickness.

footnote B), ground-face units (i.e., those ground after manufacture) must meet the face shell thickness requirements contained in the body of Table 2. In addition to minimum permissible web thicknesses for individual webs, the specification also requires a minimum total thickness of webs per foot of block length. When evaluating this equivalent web thickness, the portion of a unit to be filled with grout is exempted from the minimum requirement. This provision avoids excluding units intentionally manufactured with reduced webs, including bond beam units and open-end block, where grout fulfills the structural role of the web. For a unit to be considered a solid unit, the net cross-sectional area in every plane parallel to the bearing surface must be at least 75% of the gross cross-sectional area measured in the same plane. Minimum face shell and web thicknesses are not prescribed for solid units. The net area used to determine compressive strength is the “average” net area of the block, calculated from the unit net volume based on water displacement tests described in ASTM C 140 (ref. 8). For cored units having straight-tapered face shells and webs, average net area approximately equals the net cross-sectional area at the block mid-height. Gross and net areas of a concrete masonry unit are shown in Figure 1. Net area compressive strength is used for engineered masonry design, taking into account the mortar bedded and grouted areas. Compressive strength based on gross area is still used for masonry designed by the empirical provisions of IBC Section 2109. Maximum permissible water absorption is shown in Table 3. Absorption is a measure of the total water required to fill all voids within the net volume of concrete. It is determined from the weight-per-unit-volume difference between saturated and oven-dry concrete masonry units. Because absorption measures the water required to fill voids, aggregates with relatively large pores, such as some lightweight aggregate, would have a greater absorption than dense, nonporous aggregates, given the same compaction. As a result, lightweight units are permitted higher absorption values than medium or normal weight units. Because concrete masonry units tend to contract as they dry, ASTM C 90 limits their potential drying shrinkage to 0.065%, measured using ASTM C 426, Standard Test Method for Linear Drying Shrinkage of Concrete Masonry Units (ref. 9) 9). Finish and Appearance Finish and appearance provisions prohibit defects that would impair the strength or permanence of the construction,

Gross area* (shaded) = width (actual) x length (actual)

Net area* (shaded) = net volume (actual) height (actual) = (% solid) x (gross area) * For design calculations, a masonry element's section properties are based upon minimum specified dimensions instead of actual dimensions.

Figure 1—Gross and Net Areas

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but permit minor cracks incidental to usual manufacturing methods. For units to be used in exposed walls, the presence of objectionable imperfections is based on viewing the unit face or faces from a distance of at least 20 ft (6.1 m) under diffused lighting. Five percent of a shipment may contain chips not larger than 1 in. (25.4 mm) in any dimension, or cracks not wider than 0.02 in. (0.5 mm) and not longer than 25% of the nominal unit height. Similarly, the specification requires that color and texture be specified by the purchaser. An approved sample of at least four units, representing the range of color and texture permitted, is used to determine conformance. CONCRETE BUILDING BRICK—ASTM C 55 ASTM C 55-03 (ref. 10) included two grades of concrete brick: Grade N for veneer and facing applications and Grade S for general use. In 2006, however, the grades were removed from C 55 and requirements for concrete brick used in veneer and facing applications were moved into a new standard: C 1634 (see below). ASTM C 55-06 (ref. 11) now applies to concrete building brick only, defined as concrete masonry units with: a maximum width of 4 in. (102 mm); a weight that will typically permit it to be lifted and placed using one hand; and an intended use in nonfacing, utilitarian applications. Requirements for C 55-06 building brick include: • 2,500 psi (17.2 MPa) minimum compressive strength (average of three units), • 0.065% maximum linear drying shrinkage, • 75% minimum percent solid, and • maximum average absorption requirements of 13 pcf for normal weight brick, 15 pcf for medium weight brick and 18 pcf for lightweight brick (208, 240 and 288 kg/m3). The finish and appearance section of C 55-06 only addresses defects which might affect placement or permanence of the resulting construction. CONCRETE FACING BRICK—ASTM C 1634 The introduction of this new standard in 2006 reflects the rise in popularity of concrete brick used in architectural facing applications. A facing brick (C 1634) is distinguished

from a building brick (C 55) primarily by its intended use. ASTM C 1634 (ref. 12) defines a concrete facing brick as a concrete masonry unit with: a maximum width of 4 in. (102 mm); a weight that will typically permit it to be lifted and placed using one hand; and an intended application where one or more faces of the unit will be exposed. Compression and absorption requirements are listed in Table 4. Linear drying shrinkage, dimensional tolerances and finish and appearance requirements are similar to those in C 90, with the exception that chip size is limited to + 1/2 in. (13 mm). The minimum permissible distance between any core holes in the brick and the edge of the brick is 3/4 in. (19 mm), as it is in C 55. Both C 1634 and C 55 refer to C 140 for compression testing, which requires compression test specimens to have a height that is 60% + 10% of its least lateral dimension, to minimize the potential impact of specimen aspect ratio on tested compressive strengths. NONLOADBEARING CONCRETE MASONRY UNITS—ASTM C 129 ASTM C 129 (ref. 13) covers hollow and solid nonloadbearing units, intended for use in nonloadbearing partitions. These units are not suitable for exterior walls subjected to freezing cycles unless effectively protected from the weather. ASTM C 129 requires that these units be clearly marked to preclude their use as loadbearing units. Minimum net area compressive strength requirements are 500 psi (3.45 MPa) for an individual unit and 600 psi (4.14 MPa) average for three units. CALCIUM SILICATE FACE BRICK—ASTM C 73 ASTM C 73 (ref. 14) covers brick made from sand and lime. Two grades are included: • Grade SW—Brick intended for use where exposed to temperatures below freezing in the presence of moisture. Minimum compressive strength requirements are 4,500 psi (31 MPa) for an individual unit and 5,500 psi (37.9 MPa) for an average of three units, based on average gross area. The maximum water absorption is 15 lb/ft3 (240 kg/m3). • Grade MW—Brick intended for exposure to temperatures

Table 3—Strength and Absorption Requirements for Concrete Masonry Units, ASTM C 90 (ref. 3)A Oven-dry density Maximum water Minimum net area Weight of concrete, lb/ft3 (kg/m3) absorption, lb/ft3 (kg/m3) compressive strength, psi (MPa) classification Average of 3 units Average of 3 units Individual units Average of 3 units Individual units Lightweight Less than 105 (1,680) 18 (288) 20 (320) 1,900 (13.1) 1,700 (11.7) Medium weight 105 to less than 125 (1,680 - 2,000) 15 (240) 17 (272) 1,900 (13.1) 1,700 (11.7) Normal weight 125 (2,000) or more 13 (208) 15 (240) 1,900 (13.1) 1,700 (11.7) A

Note that ASTM C 90-01a does not include requirements for maximum water absorption of individual units. Otherwise, the requirements are identical between C 90-03 and C 90-06b. Table 4—Strength and Absorption Requirements for Concrete Facing Brick, ASTM C 1634 (ref. 12)

Oven-dry density of concrete, Density lb/ft³ (kg/m³) classification Average of 3 units Lightweight less than 105 (1,680) Medium weight 105 (1,680) to less than 125 (2,000) Normal weight 125 (2,000) or more

Minimum net area compressive strength, psi (MPa) Average of Individual 3 units units 3,500 (24.1) 3,000 (20.7) 3,500 (24.1) 3,000 (20.7) 3,500 (24.1) 3,000 (20.7)

Maximum water absorption, lb/ft³ (kg/m³) Average of Individual 3 units units 15 (240) 17 (272) 13 (208) 15 (240) 10 (160) 12 (192)

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below freezing, but unlikely to be saturated with water. Minimum compressive strength requirements are 3,000 psi (20.7 MPa) for an individual unit and 3,500 psi (24.1 MPa) for an average of three units, based on average gross area. The maximum water absorption is 18 lb/ft3 (288 kg/m3). PREFACED CONCRETE AND CALCIUM SILICATE MASONRY UNITS—ASTM C 744 ASTM C 744 (ref. 15) for prefaced units establishes requirements for the facing materials applied to masonry unit surfaces. For the concrete masonry units onto which the surface is molded, C 744 requires compliance with the requirements contained in ASTM C 55, C 90 or C 129, as appropriate. Facing requirements in C 744 include: resistance to crazing,

surface burning characteristics, adhesion, color permanence, chemical resistance, cleansability, abrasion, and dimensional tolerances. CONCRETE MASONRY UNITS FOR CATCH BASINS AND MANHOLES—ASTM C 139 ASTM C 139 (ref. 16) covers solid precast segmental concrete masonry units intended for use in catch basins and manholes. Units are required to be at least 5 in. (127 mm) thick, with a minimum gross area compressive strength of 2,500 psi (17 MPa) (average of 3 units) or 2,000 psi (13 MPa) for an individual unit, and a maximum water absorption of 10 pcf (16 kg/m³) (average of 3 units). The overall unit dimensions must be within ± 3% of the specified dimensions.

REFERENCES 1. International Building Code 2003. International Code Council, 2003. 2. International Building Code 2006. International Code Council, 2006. 3. Standard Specification for Loadbearing Concrete Masonry Units Units,, ASTM C 90-06b. ASTM International, 2006. 4.. Standard Specification for Loadbearing Concrete Masonry Units Units,, ASTM C 90-03. ASTM International, 2003. 5. Control Joints for Concrete Masonry Walls Walls—Empirical Empirical Method Method,, TEK 10-2B. National Concrete Masonry Association, 2005. 6. Control Joints for Concrete Masonry Walls Walls—Alternative Alternative Engineered Method. TEK 10-3. National Concrete Masonry Association, 2003. 7. Design and Construction of Dry-Stack Masonry Walls Walls,, TEK 14-22. National Concrete Masonry Association, 2003. 8. Standard Test Methods for Sampling and Testing Concrete Masonry Units and Related Units Units,, ASTM C 140-03. ASTM International, 2003. 9. Standard Test Method for Linear Drying Shrinkage of Concrete Masonry Units Units,, ASTM C 426-06. ASTM International, 2006. 10. Standard Specification for Concrete Brick Brick,, ASTM C 55-03. ASTM International, 2003. 11. Standard Specification for Concrete Building Brick Brick,, ASTM C 55-06. ASTM International, 2006. 12. Standard Specification for Concrete Facing Brick Brick,, ASTM C 1634-06. ASTM International, 2006. 13. Standard Specification for Nonloadbearing Concrete Masonry Units Units,, ASTM C 129-06. ASTM International, 2006. 14. Standard Specification for Calcium Silicate Brick (Sand-Lime Brick) Brick),, ASTM C 73-99a. ASTM International, 1999. 15. Standard Specification for Prefaced Concrete and Calcium Silicate Masonry Units Units,, ASTM C 744-99. ASTM International, 1999. 16. Standard Specification for Concrete Masonry Units for Construction of Catch Basins and Manholes Manholes,, ASTM C 139-05. ASTM International, 2005. 17. Specification for Masonry Structures Structures,, ACI 530.1-02/ASCE 6-02/TMS 602-02. Reported by the Masonry Standards Joint Committee, 2002. 18. Specification for Masonry Structures Structures,, ACI 530.1-05/ASCE 6-05/TMS 602-05. Reported by the Masonry Standards Joint Committee, 2005.

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NCMA and the companies disseminating this technical information disclaim any and all responsibility and liability for the accuracy and the application of the information contained in this publication. NATIONAL CONCRETE MASONRY ASSOCIATION 13750 Sunrise Valley Drive, Herndon, Virginia 20171 www.ncma.org

To order a complete TEK Manual or TEK Index, contact NCMA Publications (703) 713-19004

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SPECIFICATION FOR MASONRY STRUCTURES

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TEK 1-2C

Codes & Specs (2010)

INTRODUCTION Specification for Masonry Structures (MSJC Specification) (ref. 1) is a national consensus standard intended to be incorporated by reference into the contract documents of masonry construction projects. Compliance with this Specification is mandatory for structures designed in accordance with Building Code Requirements for Masonry Structures (MSJC Code) (ref. 2). The masonry design and construction provisions in Chapter 21 of the International Building Code (IBC) (ref. 3) are based primarily on the MSJC Code and Specification. When adopting the MSJC Code and Specification, the IBC typically amends or modifies some provisions. Because significant changes can be introduced into subsequent editions of both the MSJC and the IBC, the edition referenced by the local building code can be an important consideration when determining the specific requirements to be met. Note that building officials will often accept design and construction standards which are more current than those referenced in the applicable code, as they represent more state-of-the art requirements for the specific material or system. This TEK provides a broad overview of the MSJC Specification's content, references other NCMA TEK which describe the various provisions in greater detail, outlines updates incorporated into the 2008 edition of the MSJC Specification, and notes differences between the 2008 MSJC Specification and the 2009 IBC. THE MSJC SPECIFICATION The MSJC Specification covers material requirements, storage and handling of materials, construction, and clean-

Related TEK: 1-3C NCMA TEK 1-2C

ing, as well as provisions for quality assurance, testing and inspection. Construction includes requirements for masonry placement, bonding and anchorage, and the placement of grout, reinforcement and prestressing tendons. The document is formatted to allow the designer to modify those provisions which include a choice of alternatives. Thus, the MSJC Specification may be tailored to meet the specific needs of a project. Modifications are considered to be a supplemental specification to the MSJC Specification. The advantages of a standard specification include consistency, coordination and understanding among all parties involved. A Commentary, which accompanies the MSJC Specification, explains the mandatory requirements and further clarifies the Specification's intent. The document is written in the three-part section format of the Construction Specifications Institute. Each of the three parts (General, Products and Execution) is described in the following sections. In addition to these three parts, checklists are included at the end of the MSJC Specification to help the designer prepare the contract documents. The checklists identify the decisions that must be made when preparing any supplemental specifications. They are not a mandatory part of the Specification. Several articles of the MSJC Specification are prefaced with the phrase "when required..." These articles do not become a part of the contract documents unless action is taken by the designer to include a requirement in the supplemental specifications. Other articles are prefaced with the phrase "unless otherwise required..." These articles are a part of the contract documents unless the designer takes

Keywords: building codes, construction, quality assurance, specifications

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specific action to modify the article in the supplemental specifications. PART 1—GENERAL Part 1 of the MSJC Specification covers: • definitions, • referenced standards, • system description, which includes: 1. compressive strength requirements, 2. compressive strength determination (choice of two methods). See TEK 18-1A, Compressive Strength Evaluation of Concrete Masonry (ref. 4), for more detailed information. 3. adhered veneer requirements (choice of two methods to determine adhesion), • submittals, which includes a minimum list of required submittals. If the designer wishes to specify a higher level of quality assurance, additional submittals may be required. • quality assurance, which includes quality control measures as well as testing and inspection. The services and duties of the testing agency, inspection agency and contractor are included here (see TEK 18-3B, Concrete Masonry Inspection (ref. 5), for more detailed information), • delivery, storage and handling requirements, and • cold weather and hot weather construction requirements (see TEK 3-1C, All-Weather Concrete Masonry Construction (ref. 6)). Updates to 2008 MSJC Specification From the 2005 edition of the MSJC Specification to the 2008 edition, Tables 3, 4 and 5 which define Level A Quality Assurance, Level B Quality Assurance and Level C Quality Assurance, respectively, were revised. Columns were added to the tables to define the frequency of inspection for the various items. New inspection tasks in the tables are: • verification of the grade, type and size of anchor bolts prior to grouting for Levels B and C quality assurance, and • verification of the grade and size of prestressing tendons and anchorages for Level B quality assurance. Part 1 also includes new provisions addressing the addition of self-consolidating grout to the MSJC specification. See TEK 9-2B, Self-Consolidating Grout for Concrete Masonry (ref. 7) for further information. The 2008 Specification includes minor modifications to the provisions for verifying compliance with the specified compressive strength of masonry, f'm, using the unit strength method. In prior editions of the MSJC Specification, the unit strength table for concrete masonry implied

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that the minimum compressive strength of units could be less than the 1,900 psi (13.1 MPa) required by ASTM C90, Standard Specification for Loadbearing Concrete Masonry Units (ref 8). To avoid potential confusion, Table 2 was revised to reflect a minimum unit compressive strength of 1,900 psi (13.1 MPa). IBC Inspection Requirements The International Building Code inspection requirements are almost identical to the MSJC requirements but are organized a little differently. MSJC Level A requirements correspond to the basic inspection requirements performed by the building official as required in Section 110.3 of the IBC. The special inspection requirements of IBC for masonry are found in Section 1704.5 of that code. MSJC Level B corresponds to IBC Level 1 and MSJC Level C corresponds to IBC Level 2. IBC Section 2105 addresses quality assurance of masonry. These provisions are essentially the same as those in the MSJC Specification, with the exception that the IBC addresses testing prisms from constructed masonry. Such prisms are addressed only to a minor extent within the MSJC Specification, via one of the referenced standards, ASTM C1314-07, Standard Test Method for Compressive Strength of Masonry Prisms (ref.9). PART 2—PRODUCTS Part 2 of the MSJC Specification covers: • required material properties for masonry units, mortar, grout, reinforcement, prestressing tendons, metal accessories and other accessories such as movement joint materials. These material properties are primarily references to applicable ASTM standards. See TEKs 1-1E, ASTM Specifications for Concrete Masonry Units (ref. 10), and 12-4D, Steel Reinforcement for Concrete Masonry (ref. 11), for further information. • mortar and grout mixing requirements, found within Article 2.1 A via ASTM C270, Standard Specification for Mortar for Unit Masonry (ref. 12), and also within Article 2.6A (see TEK 3-8A, Concrete Masonry Construction (ref. 13), for more detailed information), and • reinforcement fabrication requirements. Updates to 2008 MSJC Specification The Part 2 provisions were not greatly modified between the 2005 and 2008 editions of the MSJC Specification. The reinforcement used for stirrups and lateral ties that are terminated with a standard hook is now limited to a maximum reinforcing bar size of No. 5 (M# 16), because of the difficulty of bending, placing and developing larger diameter bars in typical masonry construction.

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As in Part 1, Part 2 also includes new provisions addressing the addition of self-consolidating grout to the MSJC Specification. See TEK 9-2B, Self-Consolidating Grout for Concrete Masonry (ref. 7) for further information. IBC Masonry Material Requirements IBC Section 2103 addresses masonry construction materials, and the requirements are essentially the same as in the corresponding MSJC Specification. The IBC does include a provision for surface bonding mortar however, which is not addressed in the MSJC Specification. PART 3—EXECUTION Part 3, Execution, covers: • inspection prior to the start of masonry construction, • preparation of reinforcement and masonry prior to grouting (see TEK 3-2A, Grouting Concrete Masonry Walls (ref. 14)), • masonry erection, including site tolerances (see TEK 3-8A, Concrete Masonry Construction (ref. 13)), • bracing, which simply requires bracing to be designed and installed to assure stability (see TEK 3-4B, Bracing Masonry Walls During Construction (ref. 15) for detailed guidance), • placement of reinforcement, ties and anchors (see TEK 12-1A, Anchors and Ties for Masonry (ref. 16)), • grout placement (see TEK 3-2A, Grouting Concrete Masonry Walls (ref. 14)), • procedures for prestressing tendon installation and stressing (see TEK 3-14, Post-Tensioned Concrete Masonry Wall Construction (ref. 17)), • field quality control requirements, and • cleaning (see TEK 8-4A, Cleaning Concrete Masonry (ref. 18)).

To help ensure structural continuity between subsequent grout pours, Article 3.5F now requires a 11/2-in. (38mm) grout key (i.e., terminating the grout at least 11/2-in. (38-mm) below a mortar joint) when the previous grout lift has set before the next lift is poured. Grout keys may not be formed within masonry bond beams or lintels. IBC Construction Requirements IBC Section 2104 addresses masonry construction procedures, which essentially references the MSJC Specification without modification. In the 2006 IBC, many of the provisions of the 2005 MSJC requirements were reiterated in the IBC. In the 2009 IBC however, most of the text of these requirements was removed from the IBC and a simple reference was made to the 2008 MSJC. FINISH AND APPEARANCE The MSJC Specification addresses structural requirements only and not finish or appearance, though several Articles, such as 1.6 D Sample Panels and 3.3 F Site Tolerances certainly may affect such. Additionally, several MSJC reference standards, such as ASTM C90, Standard Specification for Loadbearing Concrete Masonry Units, specifically address this topic. Further guidance may be found by including reference to state standards such as Arizona Masonry Guild Standard 107, Levels of Quality (ref. 19), as well as to NCMA TEK 1-1E ASTM Specifications for Concrete Masonry Units and TEK 8-4A Cleaning Concrete Masonry.

Updates to 2008 MSJC Specification In addition to changes addressing self-consolidating grout, several changes have been incorporated into the Part 3 provisions, dealing with foundation dowels and with grouting procedures. MSJC Specification Article 3.4 B.8(d) is a new provision, allowing foundation dowels that interfere with masonry unit webs to be bent up to 1 in. (25 mm) horizontally for each 6 in. (152 mm) of vertical height. This provision is similar to that used in reinforced concrete construction. Article 3.5A of the MSJC Specification requires that grout be placed within 11/2 hours from the introduction of water into the mix. The 2008 edition exempts transitmixed grout from this requirement, as long as the grout meets the specified slump.

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REFERENCES 1. Specification for Masonry Structures, TMS 602/ACI 530.1/ASCE 6. Reported by the Masonry Standards Joint Committee, 2005 and 2008. 2. Building Code Requirements for Masonry Structures. TMS 402/ACI 530/ASCE 5. Reported by the Masonry Standards Joint Committee, 2005 and 2008. 3. International Building Code. International Code Council, 2006 and 2009. 4. Compressive Strength Evaluation of Concrete Masonry, TEK 18-1A. National Concrete Masonry Association, 2004. 5. Concrete Masonry Inspection, TEK 18-3B. National Concrete Masonry Association, 2006. 6. All-Weather Concrete Masonry Construction, TEK 3-1C. National Concrete Masonry Association, 2002. 7. Self-Consolidating Grout for Concrete Masonry, TEK 9-2B. National Concrete Masonry Association, 2007. 8. Standard Specification for Loadbearing Concrete Masonry Units, ASTM C90-09. ASTM International, 2009. 9. Standard Test Method for Compressive Strength of Masonry Prisms, ASTM C1314-07. ASTM International, 2007. 10. ASTM Specifications for Concrete Masonry Units, TEK 1-1E. National Concrete Masonry Association, 2007. 11. Steel Reinforcement for Concrete Masonry, 12-4D. National Concrete Masonry Association, 2007. 12. Standard Specification for Mortar for Unit Masonry, ASTM C270-07a. ASTM International, 2007. 13. Concrete Masonry Construction, TEK 3-8A. National Concrete Masonry Association, 2001. 14. Grouting Concrete Masonry Walls, TEK 3-2A. National Concrete Masonry Association, 2005. 15. Bracing Masonry Walls During Construction, TEK 3-4B. National Concrete Masonry Association, 2005. 16. Anchors and Ties for Masonry, TEK 12-1A. National Concrete Masonry Association, 2001. 17. Post-Tensioned Concrete Masonry Wall Construction, TEK 3-14. National Concrete Masonry Association, 2002. 18. Cleaning Concrete Masonry, TEK 8-4A. National Concrete Masonry Association, 2005. 19. Levels of Quality, Standard AMG 107-98. Arizona Masonry Guild, 1998.

NCMA and the companies disseminating this technical information disclaim any and all responsibility and liability for the accuracy and the application of the information contained in this publication. NATIONAL CONCRETE MASONRY ASSOCIATION

13750 Sunrise Valley Drive, Herndon, Virginia 20171 www.ncma.org To order a complete TEK Manual or TEK Index, contact NCMA Publications (703) 713-1900

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NCMA TEK 1-2C

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BUILDING CODE REQUIREMENTS FOR CONCRETE MASONRY

TEK 1-3C Codes & Specs (2007)

Keywords: building codes, construction, masonry design, quality assurance, specifications

INTRODUCTION

2003 INTERNATIONAL BUILDING CODE

The majority of jurisdictions in the United States adopt a national model code, most commonly the International Building Code (IBC) (refs. 1, 2), as the basis of their building code. The intent of the IBC is to reference and coordinate other standardized documents, rather than to develop design and construction provisions from scratch. With this in mind, the IBC masonry design and construction provisions are based primarily on Building Code Requirements for Masonry Structures (MSJC code) (refs. 3, 4) and Specification for Masonry Structures (MSJC specification) (refs. 5, 6). The code adoption process is shown schematically in Figure 1. In adopting the MSJC code and specification, the IBC typically amends or modifies some provisions. Similarly, depending on state laws, modifications can be made to the IBC at the state or local level to better suit local building practices or design traditions. However, most state codes require that any modifications to the IBC be more stringent than the corresponding requirement in the IBC. Because significant changes can be introduced into subsequent editions of both the MSJC and IBC, the edition referenced by the local building code can be an important consideration when determining the specific requirements to be met. Note that code officials will often accept more current design and construction standards than those referenced in the code, as they represent more state-of-the-art requirements for a specific material or system. To help determine which code provisions apply and highlight changes of note, this TEK outlines the major modifications to the MSJC code and specification made in the 2003 and 2006 IBC, as well as the principal changes made between the 2002 and 2005 editions of the MSJC code and specification. Note that the scope of the MSJC code and specification covers structural design and construction. Hence, requirements for items such as fire resistance, sound insulation and energy efficiency are not addressed in the MSJC documents.

The 2003 International Building Code (ref. 1) adopts by reference the 2002 editions of the MSJC code and MSJC specification (refs. 3, 5). The MSJC code covers the design of concrete masonry, clay masonry, glass unit masonry, stone masonry, as well as masonry veneer. The MSJC code requires compliance with the MSJC specification, which governs masonry construction requirements and quality assurance provisions (see also TEK 1-2B, ref. 7).

N a t i o n a l p r o c e s s

Consensus process

MSJC Code and Specification adoption with modifications and additions International Building Code adoption, possibly with modifications

State/ local process

State or Local Building Code

Figure 1—Masonry Structural Code Development Process 9

TEK 1-3C © 2007 National Concrete Masonry Association (replaces TEK 1-3B)

The 2002 MSJC Code and Specification Compared to earlier editions of the MSJC code and specification, updates included in the 2002 edition are summarized below. Masonry Design Changes to masonry design provisions included: • for the design of masonry structures, the 2002 MSJC code included new strength design provisions (see TEK 14-4A, ref. 8), offering a design method in addition to allowable stress design and empirical design, • revised seismic design requirements, including prescriptive shear wall reinforcement (see TEK 14-18A, ref. 9) and transition from Seismic Performance Categories to Seismic Design Categories (SDCs) (see TEK 14-18A, ref. 9), • for allowable stress design, revised allowable flexural tension values for unreinforced grouted masonry elements when subjected to flexural tension perpendicular to the bed joints, • new prohibition on the use of wall ties with drips (bends intended to inhibit moisture migration from one masonry wythe to the other), • for empirical design, revised wind speed threshold from a design wind pressure of 25 psf (1,197 MPa) to a wind speed of 110 mph (145 km/h) three-second gust, • for empirical design, revised shear wall spacing requirements (see TEK 14-8A, ref. 10), and • revisions to the types of masonry veneer permitted to be supported by wood construction (see TEK 3-6B, ref. 11). Construction and Quality Assurance Specification revisions included: • new corrosion protection requirements for joint reinforcement, anchors and ties depending on their intended use or exposure conditions (see TEK 12-4D, ref. 12), • new prestressed masonry quality assurance provisions for Level 2 (moderate) and Level 3 (rigorous) programs (see TEK 18-3B, ref. 13), • the addition of grout demonstration panels as a means of meeting grout pour requirements (see TEK 3-2A, ref. 14), • revised cold weather construction requirements, including new protection procedures for grouted masonry (see TEK 3-1C, ref. 15), • new veneer anchor placement requirements (see TEK 3-6B, ref. 11), and • updating of ASTM C 270 (ref. 16) mortar specification tables to include mortar cement. Differences Between the 2003 IBC and the 2002 MSJC The 2002 editions of the MSJC code and specification are included in their entirety (by reference) in the 2003 IBC. The IBC modifies several areas of the MSJC code and specification applicable to concrete masonry. The most significant of these are summarized below. In addition, quality assurance provisions are close, but not identical between the IBC and MSJC.

Seismic Design Requirements • The IBC bases loads on ASCE 7-02 (ref. 17), rather than the 1998 edition (ref. 18) referenced by the MSJC, • the IBC includes prescriptive seismic requirements for posttensioned masonry shear walls, which are not included in the MSJC, and • the IBC has some more stringent seismic requirements than the MSJC, applicable to SDCs B, C, D, E and F. Allowable Stress Design For masonry designed using allowable stress design procedures, the IBC: • modifies load combinations to be based on IBC section 1605, rather than those in MSJC code section 2.1.2.1, • modifies minimum inspections required during construction, • includes separate design requirements for columns used only to support light-frame roofs of carports, porches, sheds or similar structures with a maximum area of 450 ft2 (41.8 m2) and assigned to Seismic Design category A, B or C, • modifies the minimum required lap splice length for reinforcing bars (Note that development length and corresponding lap splice length requirements have changed frequently in recent years. NCMA recommends using the lap splice requirements published in the 2006 IBC. See TEK 12-4D (ref. 12) for more detailed information.), • sets a maximum reinforcing bar size based on the size of the cell or collar joint where the reinforcement is placed (see ref. 12), and • sets a limit on the amount of reinforcement permitted in the in-plane direction for special reinforced masonry shear walls. Strength Design For masonry designed using strength design procedures, the IBC: • sets a maximum width for the equivalent stress block of six times the nominal thickness of the masonry wall or spacing between reinforcement (whichever is less), or six times the thickness of the flange for in-plane bending of flange walls, • modifies welded and mechanical splice requirements (see ref. 12), and • adds maximum reinforcement percentage for special posttensioned masonry shear walls. Empirical Design The IBC includes empirical design procedures within the body of the code and references the MSJC code as an alternate means of compliance. However, the IBC and MSJC empirical requirements are essentially the same, except that the IBC also includes: • an exception allowing shear walls of one-story buildings to be a minimum of 6 in. (152 mm) thick, rather than 8 in. (203 mm), • provisions for empirically-designed surface-bonded masonry walls, and 10

• additional parapet wall requirements, covering flashing and copings. 2006 INTERNATIONAL BUILDING CODE The 2006 International Building Code (ref. 2) adopts by reference the 2005 editions of the MSJC code and MSJC specification (refs. 4, 6). The first section below highlights the major changes between the 2002 and 2005 MSJC code and specification. The following section summarizes important changes between the 2005 MSJC and the 2006 IBC. The 2005 MSJC Code and Specification Compared to the 2002 edition of the MSJC code and specification, the 2005 edition includes the following changes and additions. Allowable Stress Design For masonry designed using allowable stress design procedures: • the use of the one-third increase in allowable stresses has been tied to specific load combinations, • the minimum required lap splice and development lengths for reinforcing bars are the same for allowable stress design and strength design (Note that development length and corresponding lap splice length requirements have changed frequently in recent years. NCMA recommends using the lap splice requirements published in the 2006 IBC. See TEK 12-4D (ref. 12) for more detailed information.), and • in-plane allowable flexural tension has been changed from zero to be the same value as for out-of-plane flexural tension. Strength Design For masonry designed using strength design procedures: • the 2005 MSJC code includes explicit bearing strength provisions, • the modulus of rupture for in-plane bending is now the same as that for out-of-plane bending, • the maximum reinforcement limits have been modified, based on less restrictive assumptions that are related directly to the expected seismic ductility demand, • new provisions for noncontact splices have been added, • the minimum required lap splice and development lengths for reinforcing bars are the same for allowable stress design and strength design (Note that development length and corresponding lap splice length requirements have changed frequently in recent years. NCMA recommends using the lap splice requirements published in the 2006 IBC. See TEK 12-4D (ref. 12) for more detailed information.), and • provisions for computing effective compression width have been added, using the same requirements historically employed for allowable stress design.

Other Revisions The post-tensioned masonry design provisions have been updated. The most significant change is that design is now based on strength design with serviceability checks, rather than on allowable stress design with strength checks, making the design procedures easier to use for those accustomed to strength design of prestressed concrete. For grouted masonry, the maximum grout lift height has been increased from 5 ft to 12 ft-8 in (1.5 to 3.9 m) under controlled conditions, such as a consistent grout slump between 10 and 11 in. (254 and 279 mm), the absence of reinforced bond beams between the top and bottom of the grout pour, and a minimum masonry curing time of 4 hours prior to grouting. See TEK 3-2A (ref. 14) for further information. Empirical design includes several revisions to the limitations that define where empirical design can be used. In the 2002 MSJC documents, the three levels of quality assurance were designated Levels 1, 2 and 3, which were replaced by Levels A, B and C, respectively in the 2005 edition. This change in nomenclature is wholly editorial and does not affect the requirements specified for each level. For masonry veneers, prescriptive seismic requirements have been modified (several requirements that previously applied in SDC D and higher now apply in SDC E and higher), and new prescriptive requirements have been introduced for areas with high winds (wind speeds between 110 and 130 mph (177 and 209 km/hr)). Prescriptive requirements for corbelled masonry have been moved from the empirical design chapter to Chapter 1, making the corbel requirements independent of the design procedure used. In addition, design and construction provisions for autoclaved aerated concrete (AAC) appear in the MSJC for the first time. Differences Between the 2006 IBC and the 2005 MSJC The 2005 editions of the MSJC code and specification are included in their entirety (by reference) in the 2006 IBC. In addition to the modifications listed under the 2003 IBC (which are also included in the 2006 IBC unless noted below), the 2006 IBC modifies several areas of the MSJC code and specification applicable to concrete masonry. The most significant of these are summarized below. • Development length and minimum lap splice length for reinforcing bars has been updated to 48 bar diameters for Grade 60 steel, with some exceptions. See TEK 12-4D (ref. 12) for more detailed information. • Design loads and load combinations are based on ASCE 7-05 (ref. 19), rather than ASCE 7-02. • For grouted masonry, the IBC requires a "grout key" between grout pours, i.e. a horizontal construction joint formed by stopping the grout pour 11/2 in. (38 mm) below a mortar joint. • For certain special reinforced masonry shear walls, the IBC prescribes a maximum reinforcement percentage, applicable in the in-plane direction.

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REFERENCES 1. International Building Code 2003. International Code Council, 2003. 2. International Building Code 2006. International Code Council, 2006. 3. Building Code Requirements for Masonry Structures, ACI 530-02/ASCE 5-02/TMS 402-02. Reported by the Masonry Standards Joint Committee, 2002. 4. Building Code Requirements for Masonry Structures, ACI 530-05/ASCE 5-05/TMS 402-05. Reported by the Masonry Standards Joint Committee, 2005. 5. Specification for Masonry Structures, ACI 530.1-02/ASCE 6-02/TMS 602-02. Reported by the Masonry Standards Joint Committee, 2002. 6. Specification for Masonry Structures, ACI 530.1-05/ASCE 6-05/TMS 602-05. Reported by the Masonry Standards Joint Committee, 2005. 7. Specification for Masonry Structures, TEK 1-2B. National Concrete Masonry Association, 2004. 8. Strength Design of Concrete Masonry, TEK 14-4A. National Concrete Masonry Association, 2002. 9. Prescriptive Seismic Reinforcement Requirements for Masonry Structures, TEK 14-18A. National Concrete Masonry Association, 2003. 10. Empirical Design of Concrete Masonry Walls, TEK 14-8A. National Concrete Masonry Association, 2001. 11. Concrete Masonry Veneers, TEK 3-6B. National Concrete Masonry Association, 2005. 12. Steel Reinforcement for Concrete Masonry, TEK 12-4D. National Concrete Masonry Association, 2006. 13. Concrete Masonry Inspection, TEK 18-3B. National Concrete Masonry Association, 2006. 14. Grouting Concrete Masonry Walls, TEK 3-2A. National Concrete Masonry Association, 2005. 15. All-Weather Concrete Masonry Construction, TEK 3-1C. National Concrete Masonry Association, 2002. 16. Standard Specification for Mortar for Unit Masonry, ASTM C 270-99b. ASTM International, Inc., 1999. 17. Minimum Design Loads for Buildings and Other Structures, ASCE 7-02. American Society of Civil Engineers, 2002. 18. Minimum Design Loads for Buildings and Other Structures, ASCE 7-98. American Society of Civil Engineers, 1998. 19. Minimum Design Loads for Buildings and Other Structures, ASCE 7-05. American Society of Civil Engineers, 2005.

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GLOSSARY OF CONCRETE MASONRY TERMS Keywords: definitions, glossary, terminology “A” block: Hollow masonry unit with one end closed by a cross web and the opposite end open or lacking an end cross web. (See “Open end block.”) Absorption: The difference in the amount of water contained within a concrete masonry unit between saturated and ovendry conditions, expressed as weight of water per cubic foot of concrete. [4] Accelerator: A liquid or powder admixture added to a cementitious paste to speed hydration and promote early strength development. An example of an accelerator material is calcium nitrite. Adhesive anchor : An anchoring device that is placed in a predrilled hole and secured using a chemical compound. Admixture: Substance other than prescribed materials of water, aggregate and cementitious materials added to concrete, mortar or grout to improve one or more chemical or physical properties. [3] Aggregate: An inert granular or powdered material such as natural sand, manufactured sand, gravel, crushed stone, slag, fines and lightweight aggregate, which, when bound together by a cementitious matrix forms concrete, grout or mortar. [3] Air entraining: The capability of a material or process to develop a system of uniformly distributed microscopic air bubbles in a cementitious paste to increase the workability or durability of the resulting product. Some admixtures act as air entraining agents. Anchor: Metal rod, tie, bolt or strap used to secure masonry to other elements. May be cast, adhered, expanded or fastened into masonry. [1] Angle: A structural steel section that has two legs joined at 90 degrees to one another. Used as a lintel to support masonry over openings such as doors or windows in lieu of a masonry arch or reinforced masonry lintel. Also used as a shelf to vertically support masonry veneer. Sometimes referred to as a relieving angle. Arch: A vertically curved compressive structural member spanning openings or recesses. May also be built flat by using special masonry shapes or specially placed units. Area, gross cross-sectional: The area delineated by the out-toout dimensions of masonry in the plane under consideration. This includes the total area of a section perpendicular to the

TEK 1-4 Codes & Specs (2004)

direction of the load, including areas within cells and voids. [1] Area, net cross-sectional: The area of masonry units, grout and mortar crossed by the plane under consideration, based on out-to-out dimensions and neglecting the area of all voids such as ungrouted cores, open spaces, or any other area devoid of masonry. [1] Axial load: The load exerted on a wall or other structural element and acting parallel to the element’s axis. Axial loads typically act in a vertical direction, but may be otherwise depending on the type and orientation of the element. Backing: The wall or surface to which veneer is secured. The backing material may be concrete, masonry, steel framing or wood framing. [1] Beam: A structural member, typically horizontal, designed to primarily resist flexure. Burnished block: (See “Ground face block.”) Bedded area: The surface area of a masonry unit that is in contact with mortar in the plane of the mortar joint. Blast furnace slag cement: A blended cement which incorporates blast furnace slag. Blended cement: Portland cement or air-entrained portland cement combined through blending with such materials as blast furnace slag or pozzolan, which is usually fly ash. May be used as an alternative to portland cement in mortar. Block: A solid or hollow unit larger than brick-sized units. (See also “Concrete block, concrete masonry unit, masonry unit”) Block machine: Equipment used to mold, consolidate and compact shapes when manufacturing concrete masonry units. Bond: (1) The arrangement of units to provide strength, stability or a unique visual effect created by laying units in a prescribed pattern. See reference 6 for illustrations and descriptions of common masonry bond patterns. (2) The physical adhesive or mechanical binding between masonry units, mortar, grout and reinforcement. (3) To connect wythes or masonry units. Bond beam: (1) The grouted course or courses of masonry units reinforced with longitudinal bars and designed to take the longitudinal flexural and tensile forces that may be induced in a masonry wall. (2) A horizontal grouted element within masonry in which reinforcement is embedded. Bond beam block: A hollow unit with depressed webs or with "knock-out" webs (which are removed prior to placement) to accommodate horizontal reinforcement and grout. Bond breaker: A material used to prevent adhesion between two surfaces. 13

TEK 1-4 © 2004 National Concrete Masonry Association

Bond, running: The placement of masonry units such that head joints in successive courses are horizontally offset at least onequarter the unit length. [1] Centering head joints over the unit below, called center or half bond, is the most common form of running bond. A horizontal offset between head joints in successive courses of one-third and one-quarter the unit length is called third bond and quarter bond, respectively. Bond, stack: For structural design purposes, Building Code Requirements for Masonry Structures considers all masonry not laid in running bond as stack bond. [1] In common use, stack bond typically refers to masonry laid so head joints in successive courses are vertically aligned. Also called plumb joint bond, straight stack, jack bond, jack-on-jack and checkerboard bond. Bond strength: The resistance to separation of mortar from masonry units and of mortar and grout from reinforcing steel and other materials with which it is in contact. Brick: A solid or hollow manufactured masonry unit of either concrete, clay or stone. Cantilever: A member structurally supported at only one end through a fixed connection. The opposite end has no structural support. Cap block: A solid slab used as a coping unit. May contain ridges, bevels or slopes to facilitate drainage. (See also “Coping block.”) Cavity: A continuous air space between wythes of masonry or between masonry and its backup system. Typically greater than 2 in. (51 mm) in thickness. (See “Collar joint.”) Cell: The hollow space within a concrete masonry unit formed by the face shells and webs. Also called core. Cementitious material: A generic term for any inorganic material including cement, pozzolanic or other finely divided mineral admixtures or other reactive admixtures, or a mixture of such materials that sets and develops strength by chemical reaction with water. In general, the following are considered cementitious materials: portland cement, hydraulic cements, lime putty, hydrated lime, pozzolans and ground granulated blast furnace slag. [3] Cleanout/cleanout hole: An opening of sufficient size and spacing so as to allow removal of debris from the bottom of the grout space. Typically located in the first course of masonry. [2] Cold weather construction: Procedures used to construct masonry when ambient air temperature or masonry unit temperature is below 40°F (4.4°C). Collar joint: A vertical longitudinal space between wythes of masonry or between masonry wythe and backup construction, sometimes filled with mortar or grout. Typically less than 2 in. (51 mm) in thickness. [1] (See also “Cavity.”) Color (pigment): A compatible, color fast, chemically stable admixture that gives a cementitious matrix its coloring. Column: (1) In structures, a relatively long, slender structural compression member such as a post, pillar, or strut. Usually vertical, a column supports loads that act primarily in the direction of its longitudinal axis. (2) For the purposes of design, an isolated vertical member whose horizontal dimension measured at right angles to the thickness does not exceed 3 times its thickness and whose height is greater than 4 times it thickness. [1] Composite action: Transfer of stress between components of a member designed so that in resisting loads, the combined components act together as a single member. [1] Compressive strength: The maximum compressive load that a specimen will support divided by the net cross-sectional area of the specimen.

Compressive strength of masonry: Maximum compressive force resisted per unit of net cross-sectional area of masonry, determined by testing masonry prisms or as a function of individual masonry units, mortar and grout in accordance with ref. 2. [2] (See also “Specified compressive strength of masonry.”) Concrete: A composite material that consists of a water reactive binding medium, water and aggregate (usually a combination of fine aggregate and coarse aggregate) with or without admixtures. In portland cement concrete, the binder is a mixture of portland cement, water and may contain admixtures. Concrete block: A hollow or solid concrete masonry unit. Larger in size than a concrete brick. Concrete brick: A concrete hollow or solid unit smaller in size than a concrete block. Concrete masonry unit: Hollow or solid masonry unit, manufactured using low frequency, high amplitude vibration to consolidate concrete of stiff or extremely dry consistency. Connector: A mechanical device for securing two or more pieces, parts or members together; includes anchors, wall ties and fasteners. May be either structural or nonstructural. [1] Connector, tie: A metal device used to join wythes of masonry in a multiwythe wall or to attach a masonry veneer to its backing. [1] (See also “Anchor.”) Control joint: A continuous unbonded masonry joint that is formed, sawed or tooled in a masonry structure to regulate the location and amount of cracking and separation resulting from dimensional changes of different parts of the structure, thereby avoiding the development of high stresses. Coping: The materials or masonry units used to form the finished top of a wall, pier, chimney or pilaster to protect the masonry below from water penetration. Coping block: A solid concrete masonry unit intended for use as the top finished course in wall construction. Corbel: A projection of successive courses from the face of masonry. [1] Core: (See “Cell.”) Corrosion resistant: A material that is treated or coated to retard corrosive action. An example is steel that is galvanized after fabrication. Course: A horizontal layer of masonry units in a wall or, much less commonly, curved over an arch. Crack control: Methods used to control the extent, size and location of cracking in masonry including reinforcing steel, control joints and dimensional stability of masonry materials. Cull: A masonry unit that does not meet the standards or specifications and therefore has been rejected. Curing: (1) The maintenance of proper conditions of moisture and temperature during initial set to develop a required strength and reduce shrinkage in products containing portland cement. (2) The initial time period during which cementitious materials gain strength. Damp-proofing: The treatment of masonry to retard the passage or absorption of water or water vapor, either by application of a suitable coating or membrane to exposed surfaces or by use of a suitable admixture or treated cement. Damp check: An impervious horizontal layer to prevent vertical penetration of water in a wall or other masonry element. A damp check consists of either a course of solid masonry, metal or a thin layer of asphaltic or bituminous material. It is generally placed near grade to prevent upward 14 migration of moisture by capillary action.

Diaphragm: A roof or floor system designed to transmit lateral forces to shear walls or other lateral load resisting elements. [1] Dimension, actual: The measured size of a concrete masonry unit or assemblage. Dimension, nominal: The specified dimension plus an allowance for mortar joints, typically 3/8 in. (9.5 mm). Nominal dimensions are usually stated in whole numbers. Width (thickness) is given first, followed by height and then length. [1] Dimension, specified: The dimensions specified for the manufacture or construction of a unit, joint or element. Unless otherwise stated, all calculations are based on specified dimensions. Actual dimensions may vary from specified dimensions by permissible variations. [1] Dowel: A metal reinforcing bar used to connect masonry to masonry or to concrete. Drip: A groove or slot cut beneath and slightly behind the forward edge of a projecting unit or element, such as a sill, lintel or coping, to cause rainwater to drip off and prevent it from penetrating the wall. Drying shrinkage: The change in linear dimension of a concrete masonry wall or unit due to drying. Dry stack: Masonry work laid without mortar. Eccentricity: The distance between the resultant of an applied load and the centroidal axis of the masonry element under load. Effective height: Clear height of a braced member between lateral supports and used for calculating the slenderness ratio of the member. [1] Effective thickness: The assumed thickness of a member used to calculate the slenderness ratio. Efflorescence: A deposit or encrustation of soluble salts (generally white), that may form on the surface of stone, brick, concrete or mortar when moisture moves through the masonry materials and evaporates on the surface. In new construction, sometimes referred to as new building bloom. Once the structure dries, the bloom normally disappears or is removed with water. Equivalent thickness: The solid thickness to which a hollow unit would be reduced if the material in the unit were recast into a unit with the same face dimensions (height and length) but without voids. The equivalent thickness of a 100% solid unit is equal to the actual thickness. Used primarily to determine masonry fire resistance ratings. Expansion anchor: An anchoring device (based on a friction grip) in which an expandable socket expands, causing a wedge action, as a bolt is tightened into it. Face: (1) The surface of a wall or masonry unit. (2) The surface of a unit designed to be exposed in the finished masonry. Face shell: The outer wall of a hollow concrete masonry unit. [5] Face shell mortar bedding: Hollow masonry unit construction where mortar is applied only to the horizontal surface of the unit face shells and the head joints to a depth equal to the thickness of the face shell. No mortar is applied to the unit cross webs. (See also “Full mortar bedding.”) Facing: Any material forming a part of a wall and used as a finished surface. Fastener: A device used to attach components to masonry, typically nonstructural in nature. Fire resistance: A rating assigned to walls indicating the length of time a wall performs as a barrier to the passage of

flame, hot gases and heat when subjected to a standardized fire and hose stream test. For masonry, fire resistance is most often determined based on the masonry’s equivalent thickness and aggregate type. Flashing: A thin impervious material placed in mortar joints and through air spaces in masonry to prevent water penetration and to facilitate water drainage. Fly ash: The finely divided residue resulting from the combustion of ground or powdered coal. Footing: A structural element that transmits loads directly to the soil. Freeze-thaw durability: The ability to resist damage from the cyclic freezing and thawing of moisture in materials and the resultant expansion and contraction. Full mortar bedding: Masonry construction where mortar is applied to the entire horizontal surface of the masonry unit and the head joints to a depth equal to the thickness of the face shell. (See also “Face shell mortar bedding.”) Glass unit masonry: Masonry composed of glass units bonded by mortar. [1] Glazed block: A concrete masonry unit with a permanent smooth resinous tile facing applied during manufacture. Also called prefaced block. Ground face block: A concrete masonry unit in which the surface is ground to a smooth finish exposing the internal matrix and aggregate of the unit. Also called burnished or honed block. Grout: (1) A plastic mixture of cementitious materials, aggregates, water, with or without admixtures initially produced to pouring consistency without segregation of the constituents during placement. [3] (2) The hardened equivalent of such mixtures. Grout, prestressing: A cementitious mixture used to encapsulate bonded prestressing tendons. [2] Grout, self-consolidating: Highly fluid and stable grout used in high lift and low lift grouting that does not require consolidation or reconsolidation. Grout lift: An increment of grout height within a total grout pour. A grout pour consists of one or more grout lifts. [2] Grout pour: The total height of masonry to be grouted prior to erection of additional masonry. A grout pour consists of one or more grout lifts. [2] Grouted masonry: (1) Masonry construction of hollow units where hollow cells are filled with grout, or multiwythe construction in which the space between wythes is solidly filled with grout. (2) Masonry construction using solid masonry units where the interior joints and voids are filled with grout. Grouting, high lift: The technique of grouting masonry in lifts for the full height of the wall. Grouting, low lift: The technique of grouting as the wall is constructed, usually to scaffold or bond beam height, but not greater than 4 to 6 ft (1,219 to 1,829 mm), depending on code limitations. “H” block: Hollow masonry unit lacking cross webs at both ends forming an “H” in cross section. Used with reinforced masonry construction. (See also “Open end block.”) Header: A masonry unit that connects two or more adjacent wythes of masonry. Also called a bonder. [1] Height of wall: (1) The vertical distance from the foundation wall or other similar intermediate support to the top of the 15 wall. (2) The vertical distance between intermediate supports.

Height-to-thickness ratio: The height of a masonry wall divided by its nominal thickness. The thickness of cavity walls is taken as the overall thickness minus the width of the cavity. High lift grouting: (See “Grouting, high lift.”) Hollow masonry unit: A unit whose net cross-sectional area in any plane parallel to the bearing surface is less than 75 % of its gross cross-sectional area measured in the same plane. [4] Honed block: (See “Ground face block.”) Hot weather construction: Procedures used to construct masonry when ambient air temperature exceeds 100°F (37.8°C) or temperature exceeds 90°F (32.2°C) with a wind speed greater than 8 mph (13 km/h). Inspection: The observations to verify that the masonry construction meets the requirements of the applicable design standards and contract documents. Jamb block: A block specially formed for the jamb of windows or doors, generally with a vertical slot to receive window frames, etc. Also called sash block. Joint: The surface at which two members join or abut. If they are held together by mortar, the mortar-filled volume is the joint. Joint reinforcement: Steel wires placed in mortar bed joints (over the face shells in hollow masonry). Multi-wire joint reinforcement assemblies have cross wires welded between the longitudinal wires at regular intervals. Lap: (1) The distance two bars overlap when forming a splice. (2) The distance one masonry unit extends over another. Lap splice: The connection between reinforcing steel generated by overlapping the ends of the reinforcement. Lateral support: The means of bracing structural members in the horizontal span by columns, buttresses, pilasters or cross walls, or in the vertical span by beams, floors, foundations, or roofs. Lightweight aggregate: Natural or manufactured aggregate of low density, such as expanded or sintered clay, shale, slate, diatomaceous shale, perlite, vermiculite, slag, natural pumice, volcanic cinders, diatomite, sintered fly ash or industrial cinders. Lightweight concrete masonry unit: A unit whose oven-dry density is less than 105 lb/ft3 (1,680 kg/m3). [4] Lime: Calcium oxide (CaO), a general term for the various chemical and physical forms of quicklime, hydrated lime and hydraulic hydrated lime. Lintel: A beam placed or constructed over a wall opening to carry the superimposed load. Lintel block: A U-shaped masonry unit, placed with the open side up to accommodate horizontal reinforcement and grout to form a continuous beam. Also called channel block. Loadbearing: (See “Wall, loadbearing.”) Low lift grouting: (See “Grouting, low lift.”) Manufactured masonry unit: A man-made noncombustible building product intended to be laid by hand and joined by mortar, grout or other methods. [5] Masonry: An assemblage of masonry units, joined with mortar, grout or other accepted methods. [5] Masonry cement: (1) A mill-mixed cementitious material to which sand and water is added to make mortar. (2) Hydraulic cement produced for use in mortars for masonry construction. Medium weight concrete masonry unit: A unit whose ovendry density is at least 105 lb/ft3 (1,680 kg/m3) but less than

125 lb/ft3 (2,000 kg/m3). [4] Metric: The Systeme Internationale (SI), the standard international system of measurement. Hard metric refers to products or materials manufactured to metric specified dimensions. Soft metric refers to products or materials manufactured to English specified dimensions, then converted into metric dimensions. Mix design: The proportions of materials used to produce mortar, grout or concrete. Modular coordination: The designation of masonry units, door and window frames, and other construction components that fit together during construction without customization. Modular design: Construction with standardized units or dimensions for flexibility and variety in use. Moisture content: The amount of water contained within a unit at the time of sampling expressed as a percentage of the total amount of water in the unit when saturated. [4] Mortar: (1) A mixture of cementitious materials, fine aggregate water, with or without admixtures, used to construct unit masonry assemblages. [3] (2) The hardened equivalent of such mixtures. Mortar bed: A horizontal layer of mortar used to seat a masonry unit. Mortar bond: (See “Bond.”) Mortar joint, bed: The horizontal layer of mortar between masonry units. [1] Mortar joint, head: The vertical mortar joint placed between masonry units within the wythe. [1] Mortar joint profile: The finished shape of the exposed portion of the mortar joint. Common profiles include: Concave: Produced with a rounded jointer, this is the standard mortar joint unless otherwise specified. Recommended for exterior walls because it easily sheds water. Raked: A joint where 1/4 to 1/2 in. (6.4 to 13 mm) is removed from the outside of the joint. Struck: An approximately flush joint. See also “Strike.” Net section: The minimum cross section of the member under consideration. Nonloadbearing: (See “Wall, nonloadbearing.”) Normal weight concrete masonry unit: A unit whose ovendry density is 125 lb/ft3 (2000 kg/m3) or greater. [4] Open end block: A hollow unit, with one or both ends open. Used primarily with reinforced masonry construction. (See “A” block and “H” block.) Parging: (1) A coating of mortar, which may contain dampproofing ingredients, over a surface. (2) The process of applying such a coating. Pier: An isolated column of masonry or a bearing wall not bonded at the sides to associated masonry. For design, a vertical member whose horizontal dimension measured at right angles to its thickness is not less than three times its thickness nor greater than six times its thickness and whose height is less than five times its length. [1] Pigment: (See “Color.”) Pilaster: A bonded or keyed column of masonry built as part of a wall. It may be flush or project from either or both wall surfaces. It has a uniform cross section throughout its height and serves as a vertical beam, a column or both. Pilaster block: Concrete masonry units designed for use in the construction of plain or reinforced concrete masonry pilasters and columns. 16 Plain masonry: (See “Unreinforced masonry.”)

Plaster: (See "Stucco.") Plasticizer: An ingredient such as an admixture incorporated into a cementitious material to increase its workability, flexibility or extensibility. Post-tensioning: A method of prestressing in which prestressing tendons are tensioned after the masonry has been placed. [1] See also “Wall, prestressed.” Prestressing tendon: Steel element such as wire, bar or strand, used to impart prestress to masonry. [1] Prism: A small assemblage made with masonry units and mortar and sometimes grout. Primarily used for quality control purposes to assess the strength of full-scale masonry members. Prism strength: Maximum compressive force resisted per unit of net cross-sectional area of masonry, determined by testing masonry prisms. Project specifications: The written documents that specify project requirements in accordance with the service parameters and other specific criteria established by the owner or owner’s agent. Quality assurance: The administrative and procedural requirements established by the contract documents and by code to assure that constructed masonry is in compliance with the contract documents. [1] Quality control: The planned system of activities used to provide a level of quality that meets the needs of the users and the use of such a system. The objective of quality control is to provide a system that is safe, adequate, dependable and economic. The overall program involves integrating factors including: the proper specification; production to meet the full intent of the specification; inspection to determine whether the resulting material, product and service is in accordance with the specifications; and review of usage to determine any necessary revisions to the specifications. Reinforced masonry: (1) Masonry containing reinforcement in the mortar joints or grouted cores used to resist stresses. (2) Unit masonry in which reinforcement is embedded in such a manner that the component materials act together to resist applied forces. Reinforcing steel: Steel embedded in masonry in such a manner that the two materials act together to resist forces. Retarding agent: An ingredient or admixture in mortar that slows setting or hardening, most commonly in the form of finely ground gypsum. Ribbed block: A block with projecting ribs (with either a rectangular or circular profile) on the face for aesthetic purposes. Also called fluted. Sash block: (See “Jamb block.”) Scored block: A block with grooves on the face for aesthetic purposes. For example, the grooves may simulate raked joints. Screen block: An open-faced masonry unit used for decorative purposes or to partially screen areas from the sun or from view. Shell: (See “Face shell.”) Shoring and bracing: The props or posts used to temporarily support members during construction. Shrinkage: The decrease in volume due to moisture loss, decrease in temperature or carbonation of a cementitious material. Sill: A flat or slightly beveled unit set horizontally at the base of an opening in a wall. Simply supported: A member structurally supported at top and bottom or both sides through a pin-type connection, which assumes no moment transfer. Slenderness ratio: (1) The ratio of a member’s effective

height to radius of gyration. (2) The ratio of a member's height to thickness. Slump: (1) The drop in the height of a cementitious material from its original shape when in a plastic state. (2) A standardized measurement of a plastic cementitious material to determine its flow and workability. Slump block: A concrete masonry unit produced so that it slumps or sags in irregular fashion before it hardens. Slushed joint: A mortar joint filled after units are laid by “throwing” mortar in with the edge of a trowel. Solid masonry unit: A unit whose net cross-sectional area in every plane parallel to the bearing surface is 75 percent or more of its gross cross-sectional area measured in the same plane. [4] Note that Canadian standards define a solid unit as 100% solid. Spall: To flake or split away due to internal or external forces such as frost action, pressure, dimensional changes after installation, vibration, impact, or some combination. Specified dimensions: (See “Dimension, specified.”) Specified compressive strength of masonry, f'm: Minimum masonry compressive strength required by contract documents, upon which the project design is based (expressed in terms of force per unit of net cross-sectional area). [1] Split block: A concrete masonry unit with one or more faces purposely fractured to produce a rough texture for aesthetic purposes. Also called a split-faced or rock-faced block. Stirrup: Shear reinforcement in a flexural member. [1] Strike: To finish a mortar joint with a stroke of the trowel or special tool, simultaneously removing extruded mortar and smoothing the surface of the mortar remaining in the joint. Stucco: A combination of cement and aggregate mixed with a suitable amount of water to form a plastic mixture that will adhere to a surface and preserve the texture imposed on it. Temper: To moisten and mix mortar to a proper consistency. Thermal movement: Dimension change due to temperature change. Tie: (See “Connector, tie.”) Tolerance: The specified allowance in variation from a specified size, location, or placement. Tooling: Compressing and shaping the face of a mortar joint with a tool other than a trowel. See "Mortar joint profile" for definitions of common joints. Unreinforced masonry: Masonry in which the tensile resistance of the masonry is taken into consideration and the resistance of reinforcement, if present, is neglected. Also called plain masonry. [1] Veneer, adhered: Masonry veneer secured to and supported by the backing through adhesion. [2] Veneer, anchored: Masonry veneer secured to and supported laterally by the backing through anchors and supported vertically by the foundation or other structural elements. Veneer, masonry: A masonry wythe that provides the finish of a wall system and transfers out-of-plane loads directly to a backing, but is not considered to add load resisting capacity to the wall system. [1] Wall, bonded: A masonry wall in which two or more wythes are bonded to act as a composite structural unit. Wall, cavity: A multiwythe noncomposite masonry wall with a continuous air space within the wall (with or without insulation), which is tied together with metal ties. [1] Wall, composite: A multiwythe wall where the individual masonry wythes act together to resist applied loads. (See 17 also “Composite action.”)

Wall, curtain: (1) A nonloadbearing wall between columns or piers. (2) A nonloadbearing exterior wall vertically supported only at its base, or having bearing support at prescribed vertical intervals. (3) An exterior nonloadbearing wall in skeleton frame construction. Such walls may be anchored to columns, spandrel beams or floors, but not Wall, foundation: A wall below the floor nearest grade serving as a support for a wall, pier, column or other structural part of a building and in turn supported by a footing. Wall, loadbearing: Wall that supports vertical load in addition to its own weight. By code, a wall carrying vertical loads greater than 200 lb/ft (2.9 kN/m) in addition to its own weight. [1] Wall, multiwythe: Wall composed of 2 or more masonry wythes. Wall, nonloadbearing: A wall that supports no vertical load other than its own weight. By code, a wall carrying vertical loads less than 200 lb/ft (2.9 kN/m) in addition to its own weight. [1] Wall, panel: (1) An exterior nonloadbearing wall in skeleton frame construction, wholly supported at each story. (2) A nonloadbearing exterior masonry wall having bearing support at each story. Wall, partition: An interior wall without structural function. [2] Wall, prestressed: A masonry wall in which internal compressive stresses have been introduced to counteract stresses resulting from applied loads. [1] Wall, reinforced: (1) A masonry wall reinforced with steel embedded so that the two materials act together in resisting forces. (2) A wall containing reinforcement used to resist shear and tensile stresses. Wall, retaining: A wall designed to prevent the movement of soils and structures placed behind the wall. Wall, screen: A masonry wall constructed with more than 25% open area intended for decorative purposes, typically to partially screen an area from the sun or from view. Wall, shear: A wall, bearing or nonbearing, designed to resist lateral forces acting in the plane of the wall. [1] Wall, single wythe: A wall of one masonry unit thickness.

Wall, solid masonry: A wall either built of solid masonry units or built of hollow units and grouted solid. Wall tie: A metal connector that connects wythes of masonry. Wall tie, veneer: A wall tie used to connect a facing veneer to the backing. Water permeance: The ability of water to penetrate through a substance such as mortar or brick. Waterproofing: (1) The methods used to prevent moisture flow through masonry. (2) The materials used to prevent moisture flow through masonry. Water repellency: The reduction of absorption. Water repellent: Material added to the masonry to increase resistance to water penetration. Can be a surface treatment or integral water repellent admixture. Web: The portion of a hollow concrete masonry unit connecting the face shells. Weep hole: An opening left (or cut) in mortar joints or masonry face shells to allow moisture to exit the wall. Usually located immediately above flashing. Workability: The ability of mortar or grout to be easily placed and spread. Wythe: Each continuous vertical section of a wall, one masonry unit in thickness. [1] REFERENCES 1. Building Code Requirements for Masonry Structures, ACI 53002/ASCE 5-02/TMS 402-02. Reported by the Masonry Standards Joint Committee, 2002. 2. Specification for Masonry Structures, ACI 530.1-02/ASCE 6-02/ TMS 602-02. Reported by the Masonry Standards Joint Committee, 2002. 3. Standard Terminology of Mortar and Grout for Unit Masonry, ASTM C 1180-03. ASTM International, 2003. 4. Standard Terminology of Concrete Masonry Units and Related Units, ASTM C 1209-01a. ASTM International, 2001. 5. Standard Terminology of Masonry, ASTM C 1232-02. ASTM International, 2002. 6. Concrete Masonry Bond Patterns, TEK 14-6. National Concrete Masonry Association, 1999.

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Disclaimer: Although care has been taken to ensure the enclosed information is as accurate and complete as possible, NCMA does not assume responsibility for errors or omissions resulting from the use of this TEK. NATIONAL CONCRETE MASONRY ASSOCIATION 13750 Sunrise Valley Drive, Herndon, Virginia 20171 www.ncma.org



TYPICAL SIZES AND SHAPES OF CONCRETE MASONRY UNITS Keywords: architectural units, bond beams, concrete brick, dimensions, equivalent thickness, lintels, screen block, sizes and shapes INTRODUCTION Concrete masonry is one of the most versatile building products available because of the wide variety of appearances that can be achieved using concrete masonry units. Concrete masonry units are manufactured in different sizes, shapes, colors, and textures to achieve a number of finishes and functions. In addition, because of its modular nature, different concrete masonry units can be combined within the same wall to achieve variations in texture, pattern, and color. Certain concrete masonry sizes and shapes are considered standard, while others are popular only in certain regions. Local manufacturers can provide detailed information on specific products, or the feasibility of producing custom units. A more complete guide to concrete masonry units is the Shapes and Sizes Directory (ref. 2).

TEK 2-1A Unit Properties

UNIT SIZES Typically, concrete masonry units have nominal face dimensions of 8 in. (203 mm) by 16 in. (406 mm), available in nominal thicknesses of 4 , 6, 8, 10, and 12 in. (102, 152, 203, 254, and 305 mm). Nominal dimensions refer to the module size for planning bond patterns and modular layout with respect to door and window openings. Actual dimensions of concrete masonry units are typically 3/ 8 in. (9.5 mm) less than nominal dimensions, so that the 4 or 8 in. (102 or 203 mm) module is maintained with 3/ 8 in. (9.5 mm) mortar joints. Figure 1 illustrates nominal and actual dimensions for a nominal 8 x 8 x 16 in. (203 x 203 x 406 mm) concrete masonry unit. In addition to these standard sizes, other unit heights, lengths, and thicknesses may be available from local concrete masonry producers. Standard Specification for Load-Bearing Concrete Masonry Units, ASTM C 90 (ref. 5) is the most frequently referenced standard for concrete masonry units. ASTM C 90 includes minimum face shell and web thicknesses for

8" (203 mm)

8" (2 03 m m)

) mm 6 0 4 ( 16" Nominal Unit Dimensions

Stretcher unit

Single corner unit Concrete brick

75/8" (194 mm)

7 5/8"

(194 mm)

m) 97 m 3 ( " 55 /8

1 Actual Unit Dimensions

Figure 1—Nominal and Actual Unit Dimensions TEK 2-1A © 2002 National Concrete Masonry Association

Corner return unit

Double corner or plain end unit

Figure 2—Typical Concrete Masonry Units

19

(2002)

the different sizes of concrete masonry units as listed in Table 1. Overall unit dimensions (height, width, or length) are permitted to vary by ±1/8 in. (3.2 mm) from the dimensions specified by the manufacturer. Where required, units may be manufactured to closer tolerances than those permitted in ASTM C 90. ASTM C 90 also defines the difference between hollow and solid concrete masonry units. The net cross-sectional area of a solid unit is at least 75% of the gross cross-sectional area. In addition to the “standard” sizes listed above, concrete brick is available in typical lengths of 8 and 16 in. (203 and 406 mm), nominal 4 in. (102 mm) width, and a wide range of heights. They may be 100% solid, or may have two or three cores. Like ASTM C 90, Standard Specification for Concrete Building Brick, ASTM C 55 (ref. 4), permits overall unit dimensions to vary ±1/8 in. (3.2 mm) from the dimensions specified by the manufacturer. Nominal dimensions of modular concrete brick equal the actual dimensions plus 3/8 in. (9.5 mm), the thickness of one standard mortar joint. However, nominal dimensions of nonmodular sized concrete brick usually exceed the standard dimensions by 1/8 to 1/4 in. (3.2 to 6.4 mm).

UNIT SHAPES Concrete masonry unit shapes have been developed for a wide variety of applications. The most common shapes are shown in Figure 2. Typically, the face shells and webs are tapered on concrete masonry units. Depending on the core molds used in the manufacture of the units, face shells and webs may be tapered with a flare at one end, or may have a straight taper from top to bottom. The taper provides a wider surface for mortar and easier handling for the mason. The shapes illustrated in Figure 3 have been developed specifically to accommodate reinforcement. Open-ended units allow the units to be threaded around reinforcing bars. This eliminates the need to lift units over the top of the reinforcing bar, or to thread the reinforcement through the masonry cores

Table 1—Minimum Thickness of Face Shells and Webs (ref. 5) Web thickness Equivalent Face shell web thickness, Nominal width thicknessa, Websa, in./linear footb,c of unit, in. (mm) in. (mm) in. (mm) (mm/m) 3/4 (19) 3 (76) and 4 (102) 3/4 (19) 15/8 (136) d 6 (152) 1 (25) 1 (25) 21/4 (188) d 1 8 (203) 1 /4 (32) 1 (25) 21/4 (188) d 10 (254) 13/8 (35) 11/8 (29) 21/2 (209) 11/4 (32)d,e 12 (305) 11/2 (38) 11/8 (29) 21/2 (209) d,e 11/4 (32)

Open end, or "A" shaped unit

Double open end unit

Lintel unit

a

Average of measurements on 3 units taken at the thinnest point when measured as described in ASTM C 140 (ref. 3). When this standard is used for split face units, a maximum of 10% of a split face shell area is permitted to have thicknesses less than those shown, but not less than ¾ in. (19.1 mm). When the units are solid grouted, the 10% limit does not apply. b Average of measurements on 3 units taken at the thinnest point when measured as described in ASTM C 140. The minimum web thickness for units with webs closer than 1 in. (25.4 mm) apart shall be ¾ in. (19.1 mm). c Sum of the measured thickness of all webs in the unit, multiplied by 12 and divided by the length of the unit. Equivalent web thickness does not apply to the portion of the unit to be filled with grout. The length of that portion shall be deducted from the overall length of the unit for the calculation. d For solid grouted masonry construction, minimum face shell thickness not less than 5/8 in. (16 mm). e This face shell thickness is applicable where allowable design load is reduced in proportion to the reduction in thickness from basic face shell thicknesses shown, except that allowable design loads on solid grouted units shall not be reduced.

Bond beam units

Pilaster units

Figure 3—Shapes to Accommodate Reinforcement after the wall is constructed. Bond beams in concrete masonry walls can be accommodated either by saw-cutting out of a standard unit, or by using bond beam units. Bond beam units are either manufactured with reduced webs or with “knock-out” webs, which are removed prior to placement in the wall. Horizontal bond beam reinforcement is easily accommodated in these units. Lintel units are similar to the U shaped bond beam units. Lintel units are available in various depths to carry appropriate lintel loads over door and window openings. The solid bottom confines grout to the lintel. Pilaster and column units are used to easily accommodate a wall-column or wallpilaster interface, allowing space for vertical reinforcement in 20

Sash unit

All purpose or kerf unit

Control joint unit

Bevelled unit

Bull-nosed unit

Screen units

Figure 4—Special Shapes

Figure 5—Examples of Concrete Masonry Units Designed For Energy Efficiency

Figure 6—Examples of Acoustical Concrete Masonry Units

the hollow center. Figure 4 shows units developed for specific wall applications. Sash block have a vertical groove molded into one end to accommodate a window sash. Sash block can be laid with the grooves adjacent to one another to accommodate a preformed control joint gasket. Control joint units are manufactured with one male and one female end to provide lateral load transfer across control joints. An all-purpose or kerf unit contains two closely spaced webs in the center, rather than the typical single web. This allows the unit to be easily split on the jobsite, producing two 8 in. (203 mm) long units, which are typically used adjacent to openings or at the ends or corner of a wall. Bullnosed units are available with either a single or double bull nose, to soften corners. Screen units are available in many sizes and patterns. Typical applications include exterior fences, interior partitions, and openings within interior concrete masonry walls. Bevelled-end units, forming a 45o angle with the face of the unit, are used to form walls intersecting at 135o angles. Units in adjacent courses overlap to form a running bond pattern at the corner. A variety of concrete masonry units are designed to increase energy efficiency. These units, examples of which are shown in Figure 5, may have reduced web areas to reduce heat loss through the webs. Web areas can be reduced by reducing the web height or thickness, reducing the number of webs, or both. In addition, the interior face shell of the unit can be made thicker than a typical face shell for increased thermal storage, and hence further increase energy efficiency. Insulating inserts can also be incorporated into standard concrete masonry units to increase energy efficiency. Acoustical units (Figure 6) dampen sound, thus improving the noise reduction attributes of an interior space. Acoustical units are often used in schools, industrial plants, and churches, and to improve internal acoustics. SURFACE FINISHES The finished appearance of a concrete masonry wall can be varied with the size of units, shape of units, color of units and mortar, bond pattern, and surface finish of the units. The various shapes and sizes of concrete masonry units described above are often available in a choice of surface finishes. Some of the surfaces are molded into the units during the manufacturing process, while others are applied separately. Figure 7 shows some of the more common surface textures available. Ribs, flutes, striations, offsets, and scores are accomplished by using a unit mold with the desired characteristics. Split-faced units are molded with two units face-to-face and then the units are mechanically split apart. Glazed units are manufactured by bonding a permanent colored facing to a concrete masonry unit, providing a smooth impervious surface. Glazed units are often used for brightlycolored accent bands, and in gymnasiums, rest rooms, and indoor swimming pools where the stain and moisture resistant finish reduces maintenance. Glazed units comply to Standard Specification for Prefaced Concrete and Calcium Silicate Masonry Units, ASTM C 744 (ref. 6). Ground-face units are ground to achieve a smooth finish which reveals the natural colors of the aggregates. Often, specific aggregates will be used to enhance the appearance. For more information on surface finishes, see TEK 2-3A 21 Architectural Concrete Masonry Units (ref. 1).

Figure 7—Examples of Surface Finishes Available For Concrete Masonry Units (clockwise from bottom left: split face with three scores; single score ground face; glazed corner unit; ground face; ground face; single score glazed ; split face; ground face; split face; center: eight-ribbed split face)

REFERENCES 1. Architectural Concrete Masonry Units, TEK 2-3A, National Concrete Masonry Association, 2001. 2. Shapes and Sizes Directory, National Concrete Masonry Association, 1995. 3. Standard Methods of Sampling and Testing Concrete Masonry Units and Related Units, ASTM C 140-01ae1. American Society for Testing and Materials, 2001. 4. Standard Specification for Concrete Building Brick, ASTM C 55-01a. American Society for Testing and Materials, 2001. 5. Standard Specification for LoadBearing Concrete Masonry Units, ASTM C 90-01a. American Society for Testing and Materials, 2001. 6. Standard Specification for Prefaced Concrete and Calcium Silicate Masonry Units, ASTM C 744-99. American Society for Testing and Materials, 1999.

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Disclaimer: Although care has been taken to ensure the enclosed information is as accurate and complete as possible, NCMA does not assume responsibility for errors or omissions resulting from the use of this TEK.

NATIONAL CONCRETE MASONRY ASSOCIATION 13750 Sunrise Valley Drive, Herndon, Virginia 20171 www.ncma.org

To order a complete TEK Manual or TEK Index, contact NCMA Publications (703) 713-1900 22

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CONSIDERATIONS FOR USING SPECIALTY CONCRETE MASONRY UNITS INTRODUCTION Concrete masonry is an extremely versatile building product in part because of the wide variety of aesthetic effects that can be achieved using concrete masonry units. Concrete masonry units are manufactured in different sizes, shapes, colors, and textures to achieve a number of finishes and functions. In addition, because of its modular nature, different concrete masonry units can be combined within the same wall to produce variations in texture, pattern, and color. For the purposes of this TEK, “standard” concrete masonry units are considered to be two-core units (i.e., those with three cross webs), 8 in. (203 mm) high, 16 in. (406 mm) long and 4, 6, 8, 10 or 12 in. (102, 154, 203, 254 or 305 mm) wide. In addition, concrete brick is available in typical lengths of 8, 9, 12 and 16 in. (203, 229, 305 and 406 mm), nominal 4 in. (102 mm) width, and a wide range of heights. In addition to these "standard" units, many additional units have been developed for a variety of specific purposes, such as aesthetics, ease of construction and improved thermal or acoustic performance. For the purposes of this TEK, units other than those described above as standard will be referred to as specialty units. Specialty units can include units of different sizes or different unit configurations. Units of specialty configuration which are used at discreet wall locations rather than to construct an entire wall, such as sash units, pilaster units, etc. are not discussed here, nor are proprietary units discussed in detail. See TEK 2-1A, Concrete Masonry Unit Shapes and Sizes (ref. 1), for information on these units. By definition, specialty units are not available from all concrete masonry manufacturers. In some cases, such as the A- and H-shaped units used for reinforced construction,

Related TEK:

1-1E, 2-1A, 5-12, 5-15, 14-1B, 14-13B NCMA TEK 2-2B

concrete

masonry

technology

TEK 2-2B

Unit Properties (2010)

the “specialty” is commonly available in certain geographic areas. In California, for example, A- and H-shaped units are considered to be standard units. Other unit configurations discussed below may be available across the country, but from a relatively small number of producers. For this reason, it is imperative that the designer communicate with local concrete masonry manufacturers to establish the availability of the units discussed in this TEK, as well as other specialty units that may be available. Local manufacturers can provide detailed information on specific products, or the feasibility of producing custom units. Regardless of unit size or configuration, concrete masonry units are required to comply with Standard Specification for Loadbearing Concrete Masonry Units, ASTM C90 (ref. 2). See TEK 1-1E, ASTM Specifications for Concrete Masonry Units (ref. 3), for more detailed information. This TEK discusses the advantages of using specialty units, and some of the design and construction issues that may impact the use of these units SPECIALTY UNIT SIZES Concrete masonry units may be produced with widths, heights, and/or lengths other than the standard sizes listed above. Use of these units produces walls with a scale and aesthetic properties different from those built with standard-sized units. Construction productivity may be impacted by the size, weight and configuration of the units selected. Also, some of the special shapes and sizes may not be available, and may require modification on site by the contractor. One of the most important construction consideration when using specialty-sized units is modular coordination. Modular coordination is the practice of laying out

Keywords: unit shapes, unit sizes, modular coordination, section properties

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and dimensioning structures and elements to standard lengths and heights to accommodate proportioning and incorporating modular-sized building materials. Modular coordination helps maximize construction efficiency and economy by minimizing the number of units that must be cut to accommodate window and door openings, for example. See TEK 5-12, Modular Layout of Concrete Masonry (ref. 4) for information on modular coordination with standard-sized units. In addition to the specialty height units and specialty length units discussed below, veneer units (typically 4 in. (102 mm) thick) may be available in various specialty sizes, up to 16 in. high by 24 in. long (406 x 610 mm).

further information. Veneer anchor spacing requirements remain the same regardless of unit height. For units with a height greater than 8 in. (203 mm), these spacing requirements should be verified and the anchor spacing planned out prior to construction. As an example, consider 12-in. (305-mm) high veneer units installed over a concrete masonry backup wythe. The anchor spacing requirements are: maximum wall surface area supported of 2.67 ft2 (0.25 m2); maximum vertical anchor spacing of 18 in. (457 mm); and maximum horizontal anchor spacing or 32 in. (813 mm) (ref. 11). In this case, anchors need to be installed in every course to meet the requirement for a maximum vertical anchor spacing of 18 in. (457 mm). If the anchors are spaced horizontally at the maximum 32 in. (813 mm), the wall area supported is 2.67 ft2 (0.25 m2), so this veneer anchor spacing meets the code requirements. Veneer anchor spacing requirements are presented in detail in TEK 3-6B, Concrete Masonry Veneers (ref. 8). Another consideration for units with a height exceeding 8 in. (203 mm) is the use of joint reinforcement. Joint reinforcement in concrete masonry can be used to provide crack control, horizontal reinforcement in low seismic categories, and bond for multiple wythes, corners and intersections. Most requirements and rules of thumb for joint reinforcement are based on a specific area of reinforcement per foot of wall height and assume an 8-in. (203-mm) modular unit height. These should be considered prior to construction for units with heights exceeding 8 in. (203 mm). For example, empirical concrete masonry crack control criteria calls for horizontal reinforcement of at least 0.025 in.2/ft of wall height (52.9 mm2/m) between control joints. This corresponds to a maximum vertical spacing of 16 in. (406 mm) when 2-wire W1.7 (9 gage, MW11) joint reinforcement is used. When using 12-in. (305-mm) high units, the joint reinforcement of that size needs to be placed in every horizontal bed joint to meet this requirement. A better alternative is to use 2-wire W2.8 (3/16 in., MW18) joint reinforcement, with a

Specialty Unit Heights Although the most commonly available concrete masonry unit height is 8 in. (203 mm), concrete masonry units may be available in 4-in. ("half-high") or 12-in. (102and 305-mm) high units. Half-high units are gaining in popularity. They provide an aspect ratio similar to brick, but are hollow loadbearing units. See TEK 5-15, Details for Half-High Concrete Masonry Units (ref. 7) for more detailed information. As long as the unit cross-section (i.e., face shell and web thicknesses) is the same as the corresponding 8-in. (203-mm) high unit, these specialty height units can be considered to be structurally equivalent to their corresponding 8-in. (203-mm) high unit. Vertical modular coordination must be adjusted in some cases with these units. Using 4-in. (102-mm) high units provides some additional flexibility in placing wall openings, as the wall is built on a 4-in. (102-mm) vertical module rather than an 8-in. (203-mm) vertical module. With 12-in. high units, the wall height, door opening height and window opening height should ideally be a multiple of 12-in. (305-mm) to minimize cutting units on site (see Figure 1). Note that special door frames may need to be ordered to fit the masonry opening. See TEK 5-12 for

48 in. (1,219 mm)

36 in. (914 mm)

120 in. (3,048 mm) 84 in. (2,134 mm)

48 in. (1,219 mm)

88 in. (2,235 mm)

120 in. (3,048 mm)

32 in. (813 mm)

Figure 1—Vertical Modular Coordination: 12-in. (305-mm) Unit vs. Height 8-in. (203-mm) Unit Height 2

24 NCMA TEK 2-2B

maximum vertical spacing of 24 in. (610 mm), allowing the joint reinforcement to be placed every other course when using 12-in. (305-mm) high units. See TEK 10-2C, Control Joints for Concrete Masonry Walls—Empirical Method (ref. 9) for a discussion of joint reinforcement for crack control, and TEK 12-2B, Joint Reinforcement for Concrete Masonry (ref. 10), for an overview of code requirements for the use of joint reinforcement. Properties of wire for masonry (including steel cross-sectional area) can be found in Table 3 of TEK 12-4D, Steel Reinforcement for Concrete Masonry (ref. 12) Specialty Unit Lengths Specialty concrete masonry unit lengths include 18in. and 24-in. (457- and 610-mm) long units. Concrete masonry units longer than 16 in. (406 mm) are produced with the same equivalent web thickness (i.e., the average web thickness per length of wall) as 16-in. (406-mm) long units, per ASTM C90. As such, these units can be considered to be structurally equivalent to a 16-in. (305mm) long unit of the same width. Horizontal modular coordination should be considered when using these units. For example, wall length and placement of wall openings should ideally be a multiple of the unit length, as shown in Figure 2. Veneer anchor spacing and joint reinforcement considerations are the same as for standard-length units. Specialty Unit Widths In addition to the standard unit widths of 4, 6, 8, 10, and 12 in. (102, 152, 203, 254, 305 mm), specialty widths may include 14 and 16 in. (356 and 406 mm). Because unit width does not affect modular coordination, layout

36 in. (914 mm)

36 in. 36 in. 18 in. 18 in. (914 mm) (457 mm) (914 mm) (457 mm)

considerations are generally the same as for walls constructed using standard concrete masonry units. One construction issue that arises with different unit widths is corner details. TEK 5-9A, Concrete Masonry Corner Details (ref. 13), presents details to minimize cutting of units while maintaining modularity for 4, 6, 8, 10, and 12 in. (102, 152, 203, 254, 305 mm) wide units. Corner details for 14-in. (356-mm) wide units are similar to those for 12-in. (305 mm) wide units, using 8-in. (203-mm) wide units with 2 x 6 in. (51 x 152 mm) pieces of masonry to fill the gaps in the inside corners. Because 16 in. (406 mm) is a modular size, corner details for these units are similar to those for 8-in. (203-mm) wide units. A standard 8-in. (203-mm) wide unit is used in each course at the corner to maintain the running bond. Structural considerations may differ, however, as both the section properties and wall weight varies with wall width. TEKs 14-1B, Section Properties of Concrete Masonry Walls, and 14-13B, Concrete Masonry Wall Weights (refs. 5, 6), list these properties for 14 and 16 in. (356 and 406 mm) wide walls. From a construction standpoint, the larger cores of 14- and 16-in. (356 and 406 mm) wide units accommodate more reinforcement or insulation, when used, and require more grout to fill reinforced cells. SPECIALTY UNIT CONFIGURATIONS Specialty unit configuration refers to units whose crosssection varies significantly from that of a standard two-core concrete masonry unit. In this case, structural properties may be different from standard units. Modular coordination is the same as for standard units, unless the specialty configuration

32 in. (813 mm)

16 in. 40 in. 24 in. 40 in. (1,016 mm) (610 mm) (1,016 mm)(406 mm)

Figure 2—Horizontal Modular Coordination: 18-in. (457-mm) Unit Length vs. 16-in. (406-mm) Unit Length NCMA TEK 2-2B

25 3

is also produced in a specialty size. A variety of concrete masonry units have been developed to address specific performance or construction criteria. For example, units developed for improved energy efficiency may have reduced web areas to reduce heat loss through the webs, a thickened interior face shell for increased thermal storage, and/or additional cavities within the unit to accommodate insulation. Acoustical concrete masonry units provide increased sound absorption and/ or diffusion. These units may have unique construction and/or structural considerations, depending on their configuration. The concrete masonry producer should be contacted for more detailed information on the specific unit under consideration. Units to Facilitate Reinforced Construction Concrete masonry unit shapes have been developed for a wide variety of applications. The shapes illustrated in Figure 3 have been developed specifically to accommodate vertical reinforcement. Bond beam and lintel units have also been developed to accommodate horizontal

reinforcement. Open-ended units allow concrete masonry units to be inserted around vertical reinforcing bars. This eliminates the need to lift units over the top of embedded vertical reinforcement, or to thread the reinforcement through the masonry cores after the wall is constructed. Because all open cells of A- and H-shaped units are grouted and bond beam and lintel units are fully grouted, walls constructed with these units can use the same structural design parameters as for grouted standard units.

Open-ended or

Open end, or unit A-shaped "A" shaped unit

Double-open-ended

Double open end unit or H-shaped unit

Figure 3—Examples of Unit Shapes that Accommodate Reinforcement

REFERENCES 1. Concrete Masonry Unit Shapes and Sizes, TEK 2-1A. National Concrete Masonry Association, 2002. 2. Standard Specification for Loadbearing Concrete Masonry Units, ASTM C90-09. ASTM International, 2009. 3. ASTM Specifications for Concrete Masonry Units, TEK 1-1E. National Concrete Masonry Association, 2007, 4. Modular Layout of Concrete Masonry, TEK 5-12. National Concrete Masonry Association, 2008. 5. Section Properties of Concrete Masonry Walls, TEK 14-1B. National Concrete Masonry Association, 2007. 6. Concrete Masonry Wall Weights, TEK 14-13B. National Concrete Masonry Association, 2008. 7. Details for Half-High Concrete Masonry Units, TEK 5-15. National Concrete Masonry Association, 2008. 8. Concrete Masonry Veneers, TEK 3-6B. National Concrete Masonry Association, 2005. 9. Control Joints for Concrete Masonry Walls—Empirical Method, TEK 10-2C. National Concrete Masonry Association, 2010. 10. Joint Reinforcement for Concrete Masonry, TEK 12-2B. National Concrete Masonry Association, 2005. 11. Building Code Requirements for Masonry Structures, TMS 402-08/ACI 530-08/ASCE 5-08. Reported by the Masonry Standards Joint Committee, 2008. 12. Steel Reinforcement for Concrete Masonry, TEK 12-4D. National Concrete Masonry Association, 2006. 13. Concrete Masonry Corner Details, TEK 5-9A. National Concrete Masonry Association, 2004.


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26 NCMA TEK 2-2B

NCMA TEK National Concrete Masonry Association

an information series from the national authority on concrete masonry technology

ARCHITECTURAL CONCRETE MASONRY UNITS TEK 2-3A Unit Properties (2001)

Keywords: architectural units, burnished, fluted, ground face, glazed, offset face, prefaced, raked, ribbed, sandblasted, scored, slump, split-face, split-rib, striated INTRODUCTION One of the most significant architectural benefits of designing with concrete masonry is its versatility – the finished appearance of a concrete masonry wall can be varied with the unit size and shape, color of units and mortar, bond pattern, and surface finish of the units. The term “architectural concrete masonry units” typically is used to describe units displaying any one of several surface finishes that affects the texture of the unit, allowing the structural wall and finished surface to be installed in a single step. Architectural concrete masonry units are used for interior and exterior walls, partitions, terrace walls, and other enclosures. Some units are available with the same treatment or pattern on both faces, to serve as both exterior and interior finish wall material, increasing both the economic and aesthetic advantages. Architectural units comply with the same quality standards as conventional concrete masonry, Standard

(a) Split Face and Glazed

Specification for Loadbearing Concrete Masonry Units, ASTM C 90 (ref. 3). In some cases, noted below where applicable, additional provisions govern which are more applicable to the specific unit. The units described herein are some of the more common architectural concrete masonry units. However, manufacturers may carry additional products not listed here, and conversely, not all products listed will be available in all locations. Consult a local manufacturer for final unit selection. Architectural Unit TYPEs Split Faced Units Split faced units have a natural stone-like texture produced by molding two units face-to-face, then mechanically splitting them apart after curing, creating a fractured surface. Because coarse aggregate is also fractured and exposed in this process, aggregate selection can alter the final appearance. Split-faced units can also be manufactured with ribs or scores to provide strong vertical lines in the finished wall. Rough textures, like those available with split face units, are often used in areas prone to graffiti, as the texture tends to discourage graffiti vandals.

(b) Fluted Split Face

(c) Split and Ground Face

Figure 1—Examples of Architectural Concrete Masonry Units TEK 2-3A © 2001 National Concrete Masonry Association (replaces TEK 2-3)

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Ribbed Units Ribbed concrete masonry units (often called fluted units) typically have 4, 6, or 8 vertical ribs which align to form continuous vertical elements in the finished wall. The ribs are molded into the unit using a special mold. The ribs may have either a rectangular or circular profile, and may be either smooth or split for added texture. Figure 1b shows an example of a wall using ribbed (fluted) split face units. The ribs can be manufactured to project beyond the overall unit thickness (i.e., the unit thickness including ribs is thicker than a typical CMU), or with the rib projection included in the overall unit thickness. In the first case, the net area, and corresponding section properties, will be larger than those published for non-ribbed units, although the effect of this increase is typically neglected in structural calculations. In the second case, where the rib projection is included in the overall unit thickness, the designer should be aware that the actual bearing area, section modulus, and moment of inertia are less than those published for non-ribbed units. When building concrete masonry walls, mortar is typically placed to all outside edges of the masonry unit. However, with ribbed units, it is difficult to properly tool the mortar due to the projections.

Split face units are governed by ASTM C 90, which includes an allowance to account for the rough face. ASTM C 90 prescribes minimum faceshell thickness requirements for all loadbearing concrete masonry units, but also contains a variance for split face units where up to 10% of a split faceshell can be less than the minimum specified thickness, but not less than 3/4 in. (19 mm). This 10% limit does not apply, however, when the units are solidly grouted. Walls utilizing a variety of split face units are shown in Figure 1. Soft Split A soft split unit is produced using a special mold which textures the face of the unit as it is removed from the mold. The appearance from a distance is very similar to that of a split face, while a closer inspection shows a surface that is not as well defined as that achieved with a conventional split face. In addition, aggregate is not fractured in a soft split as it is in a conventional split face unit. As a result, the final appearance is not significantly affected by aggregate choice. Scored Units Scored concrete masonry units are manufactured with one or more vertical scores on the face to simulate additional mortar joints in the wall. Scored units reduce the perceived scale of the masonry while still allowing construction using full sized units. The scores are molded into the face of the unit during manufacture. Units with one vertical score are most common, and give the appearance of 8 in. x 8 in. (203 x 203 mm) units laid in stack bond. Units may also be available with 2, 3, 5, or 7 vertical scores. Figure 2a shows units with 3 vertical scores in a standard sized ground face block. It is usually desirable to lay units so that scores or ribs align vertically when the units are placed. This may require different bond patterns, depending on the configuration of the scores or ribs. For example, units with two and five scores can be placed in either stack bond or in a one-third running bond to align scores in adjacent courses. Other appropriate bond patterns are included in Table 1. Note that varying bond patterns can impact how the wall responds to structural loads (see ref. 1).

Ground Face Units (Burnished, Honed) Ground face concrete masonry units are polished after manufacture to achieve a smooth finish which reveals the natural aggregate colors. The units have the appearance of polished natural stone. The finished look of the ground surface can be altered by changing aggregate type and proportions. Often, specific aggregates will be used to enhance the appearance of the polished surface (Figure 1c and 2a), while coatings are sometimes used to deepen the color. Ground face units are often scored to achieve a scale other than the conventional 8 x 16 in. (203 x 406 mm), as shown in Figure 2a. Sandblasted Units Sand (or abrasive) blasting is used to expose the aggregate in a concrete masonry unit and results in a "weathered" look.

(a) Scored and Ground Face

(b) Glazed

(c) Slump Block

Figure 2—Additional Examples of Architectural Concrete Masonry Units

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Striated (Raked) Units Striated units achieve an overall texture by means of small vertical grooves molded into the unit face. The striations are most often random, to achieve a naturally rough look, but are sometimes available in uniform striation patterns. Striation can be applied to scored and ribbed units as well (see Figure 3c). Glazed (Prefaced) Units Glazed concrete masonry units are manufactured by bonding a permanent colored facing (typically compsed of polyester resins, silica sand and various other chemicals) to a concrete masonry unit, providing a smooth impervious surface. The glazed facings must comply with ASTM C 744 (ref. 4), Standard Specification for Prefaced Concrete and Calcium Silicate Masonry Units, which contains minimum requirements for facing quality and dimensional tolerances. In addition, the unit to which the facing is applied must comply with ASTM C 90 when used in loadbearing applications. The glazed surface is waterproof, resistant to staining and graffiti, highly impact resistant, as well as being resistant to many chemicals and bacteria. Special admixtures and mortars are available for use with glazed units that provide better stain, bacteria, and water penetration resistance. Glazed units are available in a variety of vibrant colors, pastels, earth tones, and even faux granite and marble patterns. They are often used for brightly-colored accent bands, and in gymnasiums, rest rooms, and indoor swimming pools where the stain and moisture resistant finish reduces maintenance. Kitchens and laboratories also benefit from the chemical and bacteria-resistant surface. Offset Face Units Units with an offset face produce a very highly textured wall, with strong patterns of light and shadow. The offsets make it appear as if adjacent units are staggered. This effect is accomplished by using a unit mold with the desired offsets. Slump Block Units Slump block concrete masonry units have a rounded face that resembles handmade adobe. They are more commonly available in the Southwest United States where adobe is part of the architectural heritage. Conventional concrete masonry units are manufactured using a “no-slump” concrete mix, which holds its shape when removed from the manufacturing mold. Slump units, on the other hand, are manufactured using a concrete mix that slumps within desired limits when removed from its mold (see Figure 2c). Slump unit widths may vary as much as 1 in. (25 mm). For this reason, the structural design should assume the actual width of slump units is 1 in. (25 mm) less than the nominal dimension. COLOR Architectural concrete masonry units are often integrally colored to enhance the appearance or achieve a particular effect. Concrete masonry units are colored by adding mineral oxide pigments to the concrete mix. Mortars can also be integrally colored to blend or contrast with the masonry units. The final unit color varies with the amount and type of

pigment used, cement color, aggregate color, and the amount of water used in the mix (a wetter mix will generally produce lighter and brighter colors). Both white and gray cements are available. The use of white cement results in more vibrant colors, but also increases cost. The aggregates used in the concrete mix also impact the final appearance. Because of these varying factors, there are typically some subtle variations in color among units. When units must be exactly the same color to achieve a particular architectural effect, uncolored units should be used, then painted or stained the desired color. Variegated units provide color variations within each unit, producing a marbled effect. These units are manufactured by mixing two different concrete colors into the same unit mold. Standard Unit Nomenclature As with many construction products and systems, there are often regional differences in terminology for the same type of architectural concrete masonry units: ribbed and fluted, ground and burnished, etc. The National Concrete Masonry Association has developed a standardized nomenclature (see Table 1) which can be used to avoid confusion when specifying and supplying masonry units. (See Figure 3 for examples). Table 1 – Standard Unit Nomenclature (ref. 2) Each unit is described using a three-part code in the following format: XX YYY WWHHLL, where “XX” describes the number of scores or ribs, “YYY” describes the architectural finish, and WWHHLL describes the overall nominal unit dimensions for width, height, and length. The various codes are described below. Scores or Ribs: 00 no scores or ribs, applicable for any running bond 01 one score, applicable for one-half running bond (units overlap the unit above and below by one-half the unit length) 02 2 scores, applicable for one-third running bond 03 3 scores, applicable for one-half or one-quarter running bond 04 4 ribs, applicable for one-half or one-quarter running bond 05 5 scores, applicable for one-half running bond 06 6 ribs, applicable for one-half running bond 07 7 scores, applicable for one-half or one-quarter running bond 08 8 ribs, applicable for one-half or one-quarter running bond Architectural Finish: BN1 bullnose unit with 1 in. (25 mm) radius bullnose BN2 bullnose unit with 2 in. (51 mm) radius bullnose SCV vertically scored unit GRF ground face unit MDC circular ribs, rib projects beyond the overall unit thickness MNC circular ribs, rib projection included in overall unit thickness MDR rectangular ribs, rib projects beyond the overall unit thickness MNR rectangular ribs, rib projection included in unit thickness STR striated unit STS striated unit, 1 in. (25 mm) uniform striation pattern STT striated unit, 1/16 in. (1.6 mm) uniform striation pattern SPF split face unit NPF split face ribbed unit, rib projections included in unit thickness SLP slump block **Q locally provided product

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08 MNR 080816 8 x 8 x 16 Rectangular ribbed unit (rib projection included in overall unit thickness), with 8 ribs

Figure 3a—Rectangular Ribbed Unit

06 MNC 080816 8 x 8 x 16 rounded ribbed unit (rib projection included in overall unit thickness), with 6 ribs

Figure 3b—Rounded Rib Unit

01 STR 080816 8 x 8 x 16 striated corner unit striated patterns are often applied to scored or ribbed units

Figure 3c—Striated Scored Unit

00 BN1 120816 12 x 8 x 16 Bullnose Unit with 1 in. (25 mm) radius bullnose.

Figure 3d—Bullnose Unit

Figure 3—Examples of Standard Unit Nomenclature References 1. Concrete Masonry Bond Patterns, TEK 14-6. National Concrete Masonry Association, 1996. 2. Concrete Masonry Shapes & Sizes Manual, CM 260A. National Concrete Masonry Association, 1997. 3. Standard Specification for Loadbearing Concrete Masonry Units, ASTM C 90-00. American Society for Testing and Materials, 2000. 4. Standard Specification for Prefaced Concrete and Calcium Silicate Masonry Units, ASTM C 744-99. American Society for Testing and Materials, 1999.

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30


SEGMENTAL RETAINING WALL UNITS

TEK 2-4B Unit Properties

Keywords: absorption, architectural units, compressive strength, coupon testing, dimensions, durability, erosion control, retaining wall, segmental retaining wall, specifications, testing INTRODUCTION Mortarless segmental retaining walls are a natural enhancement to a variety of landscape projects. Applications range from 8 in. (204 mm) high terraces for erosion control to retaining walls 20 ft (6.1 m) or more in height. The individual concrete units can be installed to virtually any straight or curved plan imaginable. Segmental retaining walls are used to stabilize cuts and fills adjacent to highways, driveways, buildings, patios and parking lots, and numerous other applications. Segmental retaining walls replace treated wood, cast-in-place concrete, steel, and other retaining wall systems because they are durable, easier and quicker to install, and blend naturally with the surrounding environment. Concrete units resist deterioration when exposed to the elements without addition of toxic additives which can threaten the environment.

A variety of surface textures and features are available, including split faced, stone faced, and molded face units, any one of which may be scored, ribbed, or colored to fit any project application. Construction of segmental retaining walls does not require heavy equipment access, nor does the system require special construction skills to erect. Manufactured concrete retaining wall units weigh approximately 30 to 100 lb (14 to 45 kg) each and are placed by hand on a level or sloped gravel bed. Successive courses are stacked dry on the course below in the architectural pattern desired. Mechanical interlocking and/or frictional shear strength between courses resists lateral soil pressure. In low-height walls, overturning forces due to soil pressure are resisted by the weight of the units, sometimes aided by an incline toward the retained soil. Higher walls resist lateral soil pressures by inclining the wall toward the retained

Shoreline erosion control Terracing Figure 1—Examples of Segmental Retaining Wall Installations TEK 2-4B © 2008 National Concrete Masonry Association (replaces TEK 2-4A)

31

(2008)

earth, or by other methods such as anchoring to geosynthetic reinforcement embedded in the soil. Further information on the design of segmental retaining walls can be found in Design Manual for Segmental Retaining Walls (ref. 1) and Segmental Retaining Wall Drainage Manual (ref. 2). Segmental retaining wall units are factory manufactured to quality standards in accordance with ASTM C 1372, Standard Specification for Segmental Retaining Wall Units (ref. 3). These requirements are intended to assure lasting performance, little or no maintenance, structural integrity, and continued aesthetic value. Segmental retaining wall units complying with the requirements of ASTM C 1372 have been successfully used and have demonstrated good field performance. Segmental retaining wall units currently being supplied to the market should be produced in accordance with this standard so that both the purchaser and the supplier have the assurance and understanding of the expected level of performance of the product. ASTM C 1372 covers both solid and hollow units which are to be installed without mortar (dry-stacked). Units are designed to interlock between courses or to use mechanical devices to resist sliding due to lateral soil pressure. If particular features are desired, such as a specific weight classification, higher compressive strength, surface texture, finish, color, or other special features, they should be specified separately by the purchaser. However, local suppliers should be consulted as to the availability of units with such features before specifying them. Materials ASTM C 1372 includes requirements that define acceptable cementitious materials, aggregates, and other constituents used in the manufacture of concrete segmental retaining wall units. These requirements are similar to those included in ASTM C 90, Standard Specification for Loadbearing Concrete Masonry Units (ref. 4). Compressive Strength Minimum compressive strength requirements for segmental retaining wall units are included in Table 1. Units meeting or exceeding these strengths have demonstrated the integrity needed to resist the structural demands placed on them in normal usage. These demands include impact and vibration

during transportation, the weight of the units above them in the wall, nonuniform distribution of loads between units, and the tensile stresses imposed as a result of typical wall settlement. Segmental retaining wall units will not fail in service due to compressive forces since axial loads are only a result of selfweight. Due to the direct relationship between compressive strength and tensile strength, this minimum requirement is used to ensure overall performance. Compressive strength testing of full size units is impractical due to the large size and/or unusual shape of some segmental retaining wall units. Therefore, compressive strength of these units is determined from testing coupons cut from the units. The results of tests on these smaller coupons will typically yield lower strengths than if the larger, full-size specimen were tested. The reason for the difference is size and aspect ratio. However, it is important to keep in mind that the compression test is not intended to determine the load carrying capacity of the unit, since segmental retaining walls are not designed to carry vertical structural loads. Compressive strength is used solely to determine the quality of the concrete. Because tested strengths are affected by size and shape of the specimen tested, it is important that all retaining wall units be tested using a similar size and shape. ASTM C 140, Standard Method of Sampling and Testing Concrete Masonry Units (ref. 5) requires that specimens cut from full-size units for compression testing shall be a coupon with a height to thickness ratio of 2 to 1 before capping and a length to thickness ratio of 4 to 1. The coupon width is to be as close to 2 in. (51 mm) as possible based on the configuration of the unit and the capacity of the testing machine, but not less than 1.5 in. (38 mm). The preferred size is 2 x 4 x 8 in. (51 x 102 x 203 mm) (width x height x length). The coupon height is measured in the same direction as the unit height dimension. If these procedures are followed, the compressive strength of the coupon is considered to be the strength of the whole unit. Alignment of the specimen in the compression machine is critical. Care should be taken in capping the test specimen to assure that capping surfaces are perpendicular to the vertical axis of the specimen. Saw-cutting is the required method of extracting a test specimen from a full size unit. Proper equipment and procedures are essential to prevent damaging the test specimen as a result of saw-cutting. Water-cooled, diamond-tipped blades

Table 1—Strength and Absorption Requirements (ref. 3) Minimum required net area compressive strength psi (MPa) Average of three units

Individual unit

3,000 (20.68)

2,500 (17.24)

Maximum water absorption requirements lb/ft3 (kg/m3) Weight classification—oven dry density of concrete lb/ft3 (kg/m3) Lightweight Medium weight Normal weight less than 105 (1680) to 125 (2000) 105 (1680) less than 125 (2000) or more 18 (288)

15 (240)

13 (208) 32

on a masonry table saw are recommended. The blade should have a diameter sufficient enough to make all cuts in a single pass. Manufacturers of the unit (or licensors of proprietary shapes) should be consulted about recommended locations for obtaining the compression specimen. Weight Classification Weight classifications for segmental retaining wall units are defined in Table 1. The three classifications, lightweight, medium weight, and normal weight, are a function of the oven dry density of the concrete. Most segmental retaining wall units fall into the normal weight category. Absorption Absorption requirements are also included in Table 1. This value is used to represent the volume of voids in a concrete masonry unit, including voids inside the aggregate itself. The void space is measured by determining the volume of water that can be forced into the unit under the nominal head pressure that results from immersion in a tank of water. Lightweight aggregates used in the production of lightweight and medium weight units contain voids within the aggregate itself that also fill with water during the immersion test. While reduced voids indicate a desired tightly compacted unit, tightly compacted lightweight and medium weight units will still have higher absorption due to the voids in the aggregates. For this reason the maximum allowable absorption requirements vary according to weight classification. Similar to compression testing, it generally is not practical to test full-size retaining wall units in absorption tests due to their size and weight. Therefore, ASTM C 140 permits the testing of segments saw-cut from full-size units to determine absorption and density. Sampling location typically has little effect on tested results. Absorption limits are typically expressed as mass (weight) of water absorbed per concrete unit volume. This is preferred to expressing by percentage which permits a denser unit to absorb more water than a lighter weight unit. As previously discussed, this relationship is opposite of the absorption characteristics of the material. Testing larger specimens requires particular attention to drying times, because it takes a greater length of time to remove all moisture from larger masses. ASTM C 140 requires that specimens be dried for a period of not less than 24 hours at a temperature of at least 212 °F (100 °C). The 24-hour time period does not start until the oven reaches the specified temperature. When placing larger specimens in an oven, it may take several hours for the oven to reach the prescribed temperature. ASTM C 140 then requires that specimen weights be determined every two hours to make sure that the unit is not still losing water weight (maximum weight loss in two hours must be less than 0.2% of the previous specimen weight). This will require 48 hours or more for some specimens. If not dried adequately, reported absorptions will be lower than the actual value. Permissible Variations in Dimensions Mortarless systems require consistent unit heights to

maintain vertical alignment and level of the wall. For this reason permissible variation in dimensions is limited to not more than + 1/8 in. (3.2 mm) from the specified standard dimensions. Regarding dimensions, “width” refers to the horizontal dimension of the unit measured perpendicular to the face of the wall. “Height” refers to the vertical dimension of the unit as placed in the wall. “Length” refers to the horizontal dimension of the unit measured parallel to the running length of the wall. Dimensional tolerance requirements for width are waived for split faced and other architectural surfaces. The surface is intended to be rough to satisfy the architectural features desired and can not be held to a specific tolerance. Finish and Appearance Finish and appearance requirements are virtually the same as those in ASTM C 90 for loadbearing concrete masonry units. Minor cracks incidental to the usual method of manufacture or minor chipping resulting from customary methods of handling in shipment and delivery, are not grounds for rejection. Units used in exposed wall construction are not to show chips or cracks or other imperfections in the exposed face when viewed from a distance of not less that 20 ft (6.1 m) under diffused lighting. In addition, up to five percent of a shipment are permitted to contain chips not larger than 1 in. (25.4 mm) in any dimension, or cracks not wider than 0.02 inches (0.5 mm) and not longer than 25% of the nominal height of the unit. Freeze-Thaw Durability Segmental retaining wall units may be used in aggressive freezing and thawing environments. However, freeze-thaw damage can occur when units are saturated with water and then undergo temperature cycles that range from above to below the freezing point of water. Freezing and thawing cycles and a constant source of moisture must both be present for potential damage to occur. Many variations can exist in exposure conditions, any of which may affect the freeze-thaw durability performance of the units. Such variations include: maximum and minimum temperatures, rate of temperature change, duration of temperatures, sunlight exposure, directional facing, source and amount of moisture, chemical exposure, deicing material exposure, and others. ASTM C 1372 includes three different methods of satisfying freeze-thaw durability requirements: 1. proven field performance, 2. five specimens shall each have less than 1% weight loss after 100 cycles in water using ASTM C 1262 (ref. 6), or 3. four of five specimens shall have less than 1.5% weight loss after 150 cycles in water using ASTM C 1262. Segmental retaining wall units in many areas of the country are not exposed to severe exposures. Therefore, the requirements above apply only to “areas where repeated freezing and thawing under saturated conditions occur.” Freeze-thaw durability tests can be conducted in accordance with ASTM C 1262 using water or saline as the media. For most applications, tests in water are considered sufficient. 33

If the units are to be exposed to deicing salts on a regular basis, consideration should be given to performing the tests in saline. However, no pass/fail criteria has been adopted by ASTM for saline testing. Compliance Guidance regarding compliance is also provided in ASTM C 1372. If a sample fails, the manufacturer can then remove or cull units from the shipment. Then, a new sample is selected by the purchaser from the remaining units of the shipment and tested, which is paid for by the manufacturer. If the second sample passes then the remaining units of the

lot being sampled are accepted for use in the project. If the second sample fails, however, the entire lot represented by the sample is rejected. The specification also provides guidance on responsibility for payment of the tests. Unless otherwise provided for in the contract, the purchaser typically pays for the testing if the units pass the test. However, if the units fail the test, the seller bears the cost of the testing. See TEK 18-10 Sampling and Testing Segmental Retaining Wall Units (ref. 7) for more detailed information on SRW unit sampling, testing, and acceptance.

REFERENCES 1. Design Manual for Segmental Retaining Walls, 2nd edition. National Concrete Masonry Association, 2002. 2. Segmental Retaining Wall Drainage Manual. National Concrete Masonry Association, 2002. 3. Standard Specification for Dry-Cast Segmental Retaining Wall Units, ASTM C 1372-04e2. ASTM International, 2004. 4. Standard Specification for Loadbearing Concrete Masonry Units, ASTM C 90-03. ASTM International, 2003. 5. Standard Methods of Sampling and Testing Concrete Masonry Units and Related Units, ASTM C 140-03. ASTM International, 2003. 6. Standard Test Method for Evaluating the Freeze-Thaw Durability of Manufactured Concrete Masonry Units and Related Concrete Units, ASTM C 1262-07. ASTM International, 2007. 7. Sampling and Testing Segmental Retaining Wall Units, TEK 18-10. National Concrete Masonry Association, 2005.

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SPECIFICATIONS FOR CONCRETE MASONRY ROOF PAVERS Keywords: ASTM Standards, absorption, ballasted roofs, compressive strength, durability, flexural strength, interlocking roof pavers, roof ballast, roof pavers, testing

INTRODUCTION Concrete roof pavers provide resistance to wind uplift and surface protection for roofing membranes. Concrete roof paver systems are installed over flat roofs and allow melting snow and ice, or rain water to drain from below the roof paver surface. Ballast weight of the concrete roof paver system is designed to resist uplift forces from the entire range of design wind speeds. Concrete roof pavers also provide a durable wearing surface for roof maintenance and repair operations. Specifications for concrete roof pavers included herein specify the physical requirements to ensure field performance. Also presented are methods of sampling and testing pavers to demonstrate compliance with these requirements. Concrete Roof Paver Systems Concrete roof paver systems are categorized as interlocking or non-interlocking. Interlocking systems distribute uplift forces to adjacent pavers by a tongue and groove edge connection or by a mechanical interlock between units. Noninterlocking systems resist uplift by the ballast weight of individual paver units.

Design and Execution In addition to the physical characteristics of the roof paver units themselves, parameters for design of concrete roof paver systems include the following: • Basic wind speed at building site • Building height • Parapet height • Wind gust factors • Adjacent structures and terrain features to account for obstructions in the area • Load capacity of the roof structure • Roof discontinuities • Roof slope • Weight of the units Roof structures must be designed to support the dead weight of roof paver systems. Where roof pavers are installed over existing roofs, it is important to evaluate the structural adequacy of the existing roof to support the roof pavers. Since modern roof paver systems usually contain integral drainage grooves, consideration should be given to their orientation parallel to the roof slope, min. 1/4" per foot (20 mm/m), towards roof drains. See Figure 1 for a typical concrete paver roof installation.

COUNTERFLASHING IN REGLET

Concrete Roof Paver Units Roof pavers are exposed to severe weather conditions due to their horizontal installation over flat or low slope roofs. In cold weather regions, roof pavers can be routinely subjected to freezing and thawing in a saturated condition. Typically these units will also be required to support foot traffic, loaded wheelbarrows, and other equipment without damaging the roofing membrane and insulation. These conditions require that concrete roof pavers be manufactured to specific criteria. The following specification is recommended to ensure a product of consistent quality.

TEK 2-5A © 1999 National Concrete Masonry Association (replaces TEK 2-5)

TEK 2-5A

Unit Properties

8" MAX.

CLEAT & ANGLE SECURED TO WALL RETAINER ANGLE BASE FLASHING CONCRETE ROOF PAVER MASTIC OR SEALANT

3

/ 8 " MIN. PERIMETER SPACE DECK MEMBRANE ROOFING INSULATION TREATED NAILER AS REQUIRED

Figure 1—Typical Concrete Paver Roof Installation

35

(1999)

Specification for CONCRETE ROOF PAVERS

3.1.2.1 Limestone - Limestone, with a minimum 85% calcium carbonate (CaCO3) content, shall be permitted to be added to the cement, provided the requirements of Specification C 150 as modified are met: (1) Limitation on Insoluble Residue - 1.5% (2) Limitation on Air Content of Mortar - Volume percent, 22% max. (3) Limitation on Loss on Ignition - 7%.

1. Scope 1.1 This specification covers concrete roof pavers made from portland cement, water, and mineral aggregates, with or without the inclusion of other materials, for use as roof ballast and protection of roof membranes. Note 1 – The design of roof ballast systems for resisting wind uplift is beyond the scope of this standard. Building codes and other standards should be consulted in designing for wind uplift resistance. 1.2 Concrete roof pavers covered by this specification are made from lightweight or normal weight aggregates, or both. 1.3 The values stated in inch-pound units are to be regarded as the standard. The values given in parentheses are for information only. 2. Referenced documents

2.1 ASTM Standards: C33 Specification for Concrete Aggregates C140 Methods of Sampling and Testing Concrete Masonry Units C150 Specification for Portland Cement C331 Specification for Lightweight Aggregates for Concrete Masonry Units C595/C595M Specification for Blended Hydraulic Cements C618 Specification for Fly Ash and Raw or Calcined Natural Pozzolan for Use as a Mineral Admixture in Portland Cement Concrete C989 Specification for Ground Granulated BlastFurnace Slag for Use in Concrete and Mortars C1157/C1157M Performance Specification for Blended Hydraulic Cement C1262 Standard Test Method for Evaluating the Freeze-Thaw Durability of Manufactured Concrete Masonry Units and Related Concrete Units

3. Materials 3.1 Cementitious Materials - Materials shall conform to the following applicable specifications: 3.1.1

Portland Cement - specification C 150.

3.1.2 Modified Portland Cement - Portland Cement conforming to specification C 150 modified as follows:

3.1.3 Blended Cements - Specification C 595/C 595M or C 1157/C 1157M. 3.1.4 Pozzolans - Specification C 618 3.1.5 Blast Furnace Slag - Specification C 989 3.2 Aggregates - Aggregates shall conform to the following specifications, except that grading requirements shall not necessarily apply: 3.2.1 C 33.

Normal Weight Aggregates - Specification

3.2.2 331.

Lightweight Aggregates - Specification C

3.3 Other Constituents - Air-entraining agents, coloring pigments, integral water repellents, finely ground silica, and other constituents shall be previously established as suitable for use and shall conform to applicable ASTM Standards or, shall be shown by test or experience satisfactory to the purchaser to be not detrimental to the durability of the units. 4. Physical Requirements 4.1 At the time of delivery to the purchaser, all units shall conform to the requirements prescribed in Table 1 and shall have a minimum net area average compression strength (average of 3 units) of 3000 psi (20.68 MPa) Table 1—Absorption Requirements for Concrete Roof Pavers

Concrete Density lb/ft3/(kg/m3) 95 (1522) or less over 95 to 115 (1522 to 1842) 115 (1842) or more

Maximum Water Absorption lb/ft3/(kg/m3) (average of 3 units) 15 (240) 13 (208) 10 (160)

36

with no individual unit compressive strength less than 2600 psi (17.93 MPa) when tested in accordance with Section 7.2 4.2 Resistance to Flexural Load - The average resistance to flexural load for three paver units shall exceed 350 lb (1557 N) and resistance to flexural load of each individual unit shall exceed 280 lb (1246 N) when tested in accordance with Section 7.2. 4.3 Ballast Weight—Requirements for ballast weight per unit area shall be specified separately. 4.4 Freeze-Thaw Durability—In areas where repeated freezing and thawing under saturated conditions occur, freeze-thaw durability shall be demonstrated by test or by proven field performance that the concrete roof paver units have adequate durability for the intended use. When testing is required by the specifier to demonstrate freezethaw durability, the units shall be tested in accordance with the requirement of Section 7.3. 4.4.1 Specimens shall comply with either of the following: (1) the weight loss of each of five test specimens at the conclusion of 100 cycles shall not exceed 1% of its initial weight; or (2) the weight loss of each of four or five test specimens at the conclusion of 150 cycles shall not exceed 1.5% of its initial weight. Note 2 – This standard does not include criteria for large hail stone impact. Where

required, these criteria should be specified by the purchaser. 5. Permissible Variations in Dimension and Weight 5.1 Overall dimensions for width, height, and length shall not differ by more than ± 1/8 in. (3.2 mm) from the specified standard dimensions. 5.2 Ballast weight shall not differ by more than ± 2.0 lb/ft2 (9.7 kg/m2) from the specified weight. Note 3 - Standard dimensions of units are the manufacturer’s designated dimensions. 6. Finish and Appearance 6.1 All units shall be sound and free of cracks or other defects that would interfere with the proper placement of the unit or would significantly impair the strength or permanence of the construction. Minor cracks incidental to the usual method of manufacture or minor chipping resulting from customary methods of handling in shipment and delivery, are not grounds for rejection. 6.2 Five percent of a shipment containing chips not larger than 1 in. (25.4 mm) in any dimension, or cracks not wider than 0.02 in. (0.5 mm) and not longer than 25% of the nominal height of the unit is permitted. 6.3 The color and texture of units shall be specified by the purchaser. The finished surfaces that will be

TEST FORCE DIRECTION LOAD

CUT STRIP FROM FULL PAVER 1.75" 1.75"

SPECIMEN HEIGHT (EQUAL TO SPECIMEN WIDTH)

SP EC IM EN

CAP THIS SURFACE

LE NG TH

SPECIMEN WIDTH

NEOPRENE PAD

2 X 4 WOOD BLOCK CUT TO WIDTH OF ROOF PAVER UNIT ROOF PAVER

1" DIA. STEEL ROD .90 LENGTH UNIT

NEOPRENE PAD

CAP THIS SURFACE

Figure 2—Compressive Strength Test Set-up

Figure 3—Flexural Strength Test Set-up

37

exposed in place shall conform to an approved sample consisting of not less than four units, represetning the range of texture and color permitted.

8. Compliance

7.2 Sample and test units for compressive strength, flexural load, absorption, and dimensional tolerance in accordance with Test Methods C 140.

8.1 If a sample fails to conform to the specified requirements, the manufacturer shall be permitted to remove units from the shipment. A new sample shall be selected by the purchaser from the remaining units from the shipment with a similar configuration and dimension and tested at the expense of the manufacturer. If the second sample meets the specified requirements, the remaining portion of the shipment represented by the sample meets the specified requirements. If the second sample fails to meet the specified requirements, the remaining portion of the shipment re[resented by the sample fails to meet the specified requirements.

7.3 When required, sample and test five specimens for freeze-thaw durability in water in accordance with C 1262. Freeze-thaw durability shall be based on tests of units made with the same materials, concrete mix design, manufacturing process, and curing method, conducted not more than 24 months prior to delivery.

Note 4 - Unless otherwise spcified in the purchase order, the cost of the test is typically borne as follows: (1) if the results of the tests show that the units do not conform to the requirements of this specification, the cost is typically borne by the seller; (2) if the results of the tests show that the units conform to the specification requirements, the cost is typically borne by the purchaser.

7. Sampling and Testing 7.1 The purchaser or authorized representative shall be accorded proper facilities to inspect and sample the units at the place of manufacture from the lots ready for delivery.

Provided by:

NCMA and the companies disseminating this technical information disclaim any and all responsibility and liability for the accuracy and the application of the information contained in this publication.

NATIONAL CONCRETE MASONRY ASSOCIATION 2302 Horse Pen Road, Herndon, Virginia 22071-3499 www.ncma.org



DENSITY-RELATED PROPERTIES OF CONCRETE MASONRY ASSEMBLIES Keywords: acoustics, aesthetics, compressive strength, concrete density, energy efficiency, fire resistance rating, movement control, productivity, water penetration resistance

INTRODUCTION The versatility of concrete masonry as a construction assembly is well established through the variety of applications and structures it is used to create. Concrete masonry offers almost limitless combinations of color, shape, size, strength, texture, and density. This TEK illustrates the various physical and design properties influenced by the density of concrete masonry units, and provides references to guide the user towards a fuller discussion and more detailed information. Although most of the following discussions use lightweight and normal weight concrete masonry as examples, the properties of medium weight masonry can typically be expected to fall between the two. Note that while some of these density-related properties, such as sound transmission loss, may be directly referenced in building codes such as the International Building Code (ref. 1), other properties or characteristics, such as aesthetics and construction productivity fall outside the scope of the building code. BASICS OF CONCRETE MASONRY UNIT DENSITY The density of a concrete masonry unit is expressed as the oven-dry density of concrete in pounds per cubic foot (lb/ft3 [kg/m3]) as determined in accordance with ASTM C 140, Standard Test Methods for Sampling and Testing Concrete Masonry Units and Related Units (ref. 2). In production, the density of a given concrete masonry unit is controlled in part by the methods used to manufacture the unit, but largely by the type of aggregate used in production. Through the use of lightweight aggregates, normal weight aggregates, or blends of lightweight and normal weight aggregates, the resulting density of concrete masonry units can be varied by the producer to achieve one or more desired physical properties. ASTM C 90, Standard Specification for Loadbearing

TEK 2-6 Unit Properties (2008)

Concrete Masonry Units (ref. 3) defines three density classes for concrete masonry units: • Lightweight – units having an average density less than 105 lb/ft3 (1,680 kg/m3). • Medium Weight – units having an average density of 105 lb/ft3 (1,680 kg/m3) or more, but less than 125 lb/ft3 (2,000 kg/m3). • Normal Weight – units having an average density of 125 lb/ft3 (2,000 kg/m3) or more. When a specific density classification or density range is desired for a project, it should be specified in the project documents along with the other physical properties of the concrete masonry units such as size, strength, color, and texture. Before specifying a specific density range, designers are encouraged to first consult with manufacturers local to the project for availability. As with all physical properties of concrete masonry, minor variation in density from unit to unit and from batch to batch should be expected. In accordance with ASTM C 90, aggregates used to manufacture concrete masonry units must conform to either ASTM C 33, Standard Specification for Concrete Aggregates (ref. 4), or ASTM C 331, Standard Specification for Lightweight Aggregates for Concrete Masonry Units (ref. 5). Whereas normal weight aggregates are typically mined or quarried, lightweight aggregates may be manufactured, mined or quarried from a natural source, or a by-product of another process. Although not all aggregate types are produced in all areas of the country, non-local aggregates may be available. If a concrete masonry unit of a specific aggregate type is desired, potential suppliers should be consulted for availability prior to specifying them. FIRE RESISTANCE Fire resistance ratings of one to four hours can be achieved with concrete masonry of various widths (or thicknesses), configurations and densities. As outlined in TEK 7-1A, Fire Resistance Rating of Concrete Masonry Assemblies (ref. 6), the fire resistance rating of a concrete masonry assembly can be determined by physical testing, through a listing service, or by a standardized calculation procedure. Whether through direct measurement or by cal39


culation, the fire resistance rating of a given concrete masonry assembly varies directly with the aggregate type and with the volume of concrete in the unit, expressed as the equivalent thickness. Through extensive testing and analysis, empirical relationships have been established between the fire resistance rating of a concrete masonry assembly and the corresponding type of aggregate and equivalent thickness of the unit used to construct the assembly. These relationships are summarized in Figure 1. These relationships between aggregate type/equivalent thickness and the corresponding fire resistance rating are shown graphically in Figure 2. Note that equivalent thicknesses used in Figure 2 are for illustration only, and represent typical equivalent thicknesses for standard hollow concrete masonry units. Actual units may have higher or lower equivalent thicknesses than those shown, with corresponding higher or lower fire resistance ratings. In general, 8-in. (203-mm) and wider concrete masonry units can be supplied with fire resistance ratings up to four hours. For example, a typical hollow 8 in. (203 mm) concrete masonry unit with an equivalent (solid) thickness of 4.0 in. (102 mm), can have a calculated fire resistance rating from 1.8 hours to 3 hours, depending on the type of aggregate used to produce the unit. SOUND CONTROL The control of sound between adjacent dwelling units or between dwelling units and public areas is an important design consideration for user comfort. Sound Transmission Class (STC), expressed in decibels (dB), is a single number rating that provides a measure of the sound insulating properties of walls. The higher the STC rating, the better the assembly can block or reduce the transmission of sound across it. For concrete masonry construction, STC

can be calculated using the installed weight of the assembly, which is a function of the unit density, unit size and configuration, presence of surface finishes, and presence of grout or other cell-fill materials such as sand. See Sound Transmission Class Ratings for Concrete Masonry Walls, TEK 13-1B (ref. 7) for a full discussion. In accordance with Standard Method for Determining the Sound Transmission Class Rating for Masonry Walls (ref. 8), the STC rating for single wythe concrete masonry assemblies without additional surface treatments is determined by the following equation: STC = 19.6W0.230 Eqn. 1. SI STC = 13.6W0.230 Where W = the average wall weight based on the weight of: the masonry units; the weight of mortar, grout and loose fill material in the voids within the wall; and the weight of surface treatments (excluding drywall) and other wall components, lb/ft2 (kg/m2). All other design variables being equal, the STC value of masonry construction increases with increasing unit density. Note that STC values determined by the calculation tend to be conservative. Generally, higher STC values are obtained by referring to actual tests than by the calculation. In addition to the STC rating, the value of the Noise Reduction Coefficient (NRC) can also be influenced to some extent by concrete unit density. NRC measures the ability of a surface to absorb sound (based on a scale of 0 to 1), which can be an important characteristic in some applications, such as concert halls and assembly areas. A higher NRC value indicates that more sound is absorbed by an assembly. NRC values for concrete masonry walls are tabulated according to: the application of any coatings to the wall, the surface texture (coarse, medium or fine) and the density classification (lightweight or normal weight).

Aggregate type in the concrete masonry unit2 Calcareous or siliceous gravel the equi . 4 ) .0 5 in thicknes Limestone, cin7 8 mm (103 4 in. 4 mm particula ders or slag (19 ) solid un Expanded clay, The equivalent thickness of this particular unit (a shale or slate solid unit with the same amount of material) is Expanded slag or 4.04 in. (103 mm). pumice

Minimum required equivalent thickness for fire resistance rating, in. (mm)1 4 hr 3 hr 2 hr 1.5 hr 1 hr 0.75 hr 0.5 hr 6.2 (157) 5.9 (150) 5.0 (130) 4.7 (119)

5.3 (135) 5.0 (127) 4.4 (112) 4.0 (102)

4.2 (107) 4.0 (102) 3.6 (91) 3.2 (81)

3.6 (91) 3.4 (86) 3.3 (84) 2.7 (69)

2.8 (71) 2.7 (69) 2.6 (66) 2.1 (53)

2.4 (61) 2.3 (58) 2.2 (56) 1.9 (48)

2.0 (51) 1.9 (48) 1.8 (46) 1.5 (38)

1

Fire resistance ratings between the hourly fire resistance rating periods listed may be determined by linear interpolation based on the equivalent thickness value of the concrete masonry assembly. 2 Minimum required equivalent thickness corresponding to the hourly fire resistance rating for units made with a combination of aggregates shall be determined by linear interpolation based on the percent by volume of each aggregate used in the manufacture. Figure 1— Calculated Fire Resistance Rating for Single Wythe Concrete Masonry Walls 40

7

6

180

160

Typical equivalent thickness of a hollow 16 in. (406 mm) Typical equivalent thickness of a hollow 14 in. (356 mm) unit

140

Typical equivalent thickness of a hollow 12 in. (305 mm) unit

120

Typical equivalent thickness of a hollow 10 in. (254 mm) unit 4

Typical equivalent thickness of a hollow 8 in. (203 mm) unit 100 Typical equivalent thickness of a hollow 6 in. (152 mm) unit 80

3 Typical equivalent thickness of a hollow 4 in. (102 mm) unit

60

Equivalent thickness, mm

Equivalent thickness, in.

5

2 40 1 20

0

0 0.5

0.75

Calcareous or siliceous gravel

1

1.5 Fire resistance, hr

Limestone, cinders, or slag

2

3

Expanded clay, shale, or slate

4 Expanded slag or pumice

Figure 2—Calculated Fire Resistance Ratings Assuming a similar surface texture and coating, a concrete masonry wall constructed with lightweight units will have a higher NRC than a companion wall constructed with normal weight units, due to the larger pore structure often associated with lower density units. Painting or coating the surface of the concrete masonry assembly reduces the NRC for both lightweight and normal weight concrete masonry. See Noise Control with Concrete Masonry, TEK 13-2A (ref. 9) for a full discussion.

Table 1—Absorption Requirements for Concrete Masonry Units Density Maximum water absorption, lb/ft3 (kg/m3) classification Average of 3 units Individual unit Lightweight 18 (288) 20 (320) Medium weight 15 (240) 17 (272) Normal weight 13 (208) 15 (240) WATER PENETRATION AND ABSORPTION

COMPRESSIVE STRENGTH Regardless of unit density, all loadbearing concrete masonry units meeting the physical properties of ASTM C 90 (ref. 3) must have a minimum average compressive strength of 1,900 psi (13.1 MPa). It is possible to produce concrete masonry units that meet or exceed the ASTM C 90 minimum strength in any density classification, although not all combinations of physical properties may be commonly available in all regions. Therefore, local producers should always be consulted for product availability before specifying. In general, for a given concrete masonry unit mix design, higher compressive strengths can be achieved by increasing the unit density through adjustments to the manufacturing methods. (ref. 16).

Concrete masonry unit specifications typically establish upper limits on the amount of water permitted to be absorbed. Expressed in pounds of water per cubic foot of concrete (kilograms of water per cubic meter of concrete), these limits vary with the density classification of the unit, as shown in Table 1. While the absorption values are not directly related to unit physical properties such as compressive strength and resistance to mechanisms of deterioration such as freezethaw, they do provide a measurement of the void structure within the concrete matrix of the unit. Several production variables can affect the void structure, including degree of compaction, water content of the plastic mix, and aggregate gradation. Due to the vesicular structure of lower density units, there is a potential for higher measured absorption than is typical for most higher density units. Consequently, 41

ASTM C 90 permits lower density units to have a higher maximum absorption value. The higher absorption limits permitted by ASTM C 90 for lower density units do not necessarily correlate to reduced water penetration resistance. One reason is that water penetration resistance is known to be highly affected by workmanship and dependent on detailing for water management. It is generally recognized that these two factors more heavily influence the wall’s water penetration resistance than do other factors, such as unit density. AESTHETIC CONSIDERATIONS One of the most significant architectural benefits of designing with concrete masonry is the versatility afforded by the layout and appearance of the finished assembly, which can be varied with the unit size and shape, color of the units and mortar, bond pattern, and surface finish of the units. The term “architectural concrete masonry unit” (ref. 10) is often used to generically describe units exhibiting any number of surface finishes or colors. Loadbearing single wythe masonry walls constructed with these units uniquely offer the designer structural function, envelope enclosure and the aesthetics of a finished wall surface without the need for additional materials, components or assemblies. In general, the many options available for architectural concrete masonry units can be offered in any of the three unit density classifications. However, with respect to unit appearance, any change in aggregates (whether a change in source or a change in aggregate type) used to manufacture a concrete masonry unit may change its color or texture, particularly for units with mechanically altered features such as split or ground-face surfaces. As a result, when aesthetics are an important consideration, sample units submitted for conceptual design should incorporate the specific aggregate intended to be used in the actual production of the units. Note that various degrees of surface “smoothness” (tight, fine, medium, coarse) can be obtained using the same aggregate by varying the mix design (proportions and moisture), aggregate gradation, aggregate shape, and degree of compaction during manufacture. In addition to production variables, the appearance of the finished masonry is also affected by workmanship, and the mortar color and jointing. Where color, texture and finish are of particular concern, the designer should specify a special sample panel for review and approval during the submittal process (ref. 1, 17). ENERGY EFFICIENCY When selecting masonry for its energy efficiency, two material thermal properties should be considered: • R-value—a material’s ability to resist the transfer of heat under steady-state conditions; and • Thermal mass (heat capacity)—a material’s ability to store and release heat (ref. 11). These physical properties, in combination with a building’s design, layout, location, climate, exposure, use,

or occupancy as required by building codes, influence the energy efficiency and thermal characteristics of the building envelope and of the building. Increasing the unit density, unit thickness, unit solid content, and amount/extent of grout, increases the installed weight of the masonry assembly, which is directly related to its heat capacity. (ref. 11). Conversely, increasing the density or amount of grout used in a concrete masonry assembly decreases its R-value (ref. 12). Because of the multitude of variables that determine the overall energy efficiency of a structure, some projects benefit more by increasing the thermal mass of an assembly while others see more energy efficiency by increasing the R-value. As such, the unique requirements of each project should be considered individually for maximum benefit. STRUCTURAL DESIGN INFLUENCES The structural design of masonry is based on the specified compressive strength of masonry, f'm, which is a function of the compressive strength of the unit and the type of mortar used in construction. It is possible to produce a wide range of compressive strengths within each of the density classes. Therefore, for a given unit compressive strength and mortar type, the strength of the masonry assembly is unaffected by the unit density. As such, the design flexural, shear, and bearing strengths of masonry, some deformational properties such as elastic modulus, and the structural behavior of the masonry assembly determined by contemporary codes and standards are independent of the density of the concrete masonry unit. Unit density, however, can influence other structural design considerations, aside from compressive strength. Reducing the density of a concrete masonry unit can reduce the overall weight of a structure, and potentially reduce the required size of the supporting foundation, slab, or beam. Reducing the weight of a structure or element also reduces the seismic load a structure or element must be designed to resist, because the magnitude of seismic loading is a direct function of dead load. As with thermal mass and sound control, there may be circumstances where increasing the unit density is structurally beneficial. For example, the structural stability against overturning and uplift is increased with increasing structural weight. Hence, while increased structural dead load increases seismic design forces, it also concurrently helps to resist wind loads. Therefore, there may be some structural advantage to using lightweight units in areas of high seismic risk; and normal weight units in areas prone to high winds, hurricanes and/or tornadoes. Structural design considerations, however, are often relatively minor compared to other factors that may influence the choice of unit density. PRODUCTIVITY For a given unit configuration, and with all other factors affecting production being equal, lower unit weights 42

typically enable a mason to lay more units within a given timeframe (ref. 13). Other factors influencing the daily productivity of a mason may include environmental conditions, unit size and shape, building size and configuration, masonry bond pattern, and reinforcement and other detailing (ref. 13). MOVEMENT CONTROL Regardless of the density of a concrete masonry unit, the established movement control recommendations for concrete masonry construction are applicable. See Crack Control in Concrete Masonry Walls, TEK 10-1A, and Control Joints for Concrete Masonry Walls – Empirical Method, TEK 10-2B (refs. 14, 15) for more detailed guidance. ASTM C 90 requires that linear drying shrinkage of all concrete masonry units, regardless of unit density, not exceed 0.065% at the time of delivery to the jobsite. However, despite the fact that not all concrete masonry units exhibit the same linear drying shrinkage within this limit, established movement control recommendations (refs. 14, 15) are independent of the concrete masonry unit density. SUMMARY Issues of masonry design and construction can be influenced and addressed to varying extents through the choice of concrete masonry unit density, but generally the resulting effects of varying unit density on masonry behavior and performance are quite limited. Notwithstanding these effects, the designer can be assured that concrete masonry constructed of any unit density offers sufficient flexibility and alternatives in the choice of materials, design, and construction detailing to satisfy the structural and architectural requirements of the project. REFERENCES 1. International Building Code. International Code Council, 2003 and 2006. 2. Standard Test Methods for Sampling and Testing Concrete Masonry Units and Related Units, ASTM C 140-06,

ASTM International, 2006. 3. Standard Specification for Loadbearing Concrete Masonry Units, ASTM C 90-06a, ASTM International, 2006. 4. Standard Specification for Concrete Aggregates, ASTM C 33-03, ASTM International, 2006. 5. Standard Specification for Lightweight Aggregates for Concrete Masonry Units, ASTM C 331-05, ASTM International, 2006. 6. Fire Resistance Rating of Concrete Masonry Assemblies, TEK 7-1A, National Concrete Masonry Association, 2006. 7. Sound Transmission Class Ratings for Concrete Masonry Walls, TEK 13-1B, National Concrete Masonry Association, 2007. 8. Standard Method for Determining the Sound Transmission Class Rating for Masonry Walls, TMS 0302-07, The Masonry Society, 2007. 9. Noise Control with Concrete Masonry, TEK 13-2A, National Concrete Masonry Association, 2007. 10. Architectural Concrete Masonry Units, TEK 2-3A, National Concrete Masonry Association, 2001. 11. Heat Capacity (HC) Values for Concrete Masonry Walls, TEK 6-16, National Concrete Masonry Association, 1989. 12. R-Values for Single Wythe Concrete Masonry Walls, TEK 6-2A, National Concrete Masonry Association, 2005. 13. Productivity and Modular Coordination in Concrete Masonry Construction, TEK 4-1A, National Concrete Masonry Association, 2002. 14. Crack Control in Concrete Masonry Walls, TEK 10-1A, National Concrete Masonry Association, 2005. 15. Control Joints for Concrete Masonry Walls – Empirical Method, TEK 10-2B. National Concrete Masonry Association, 2005. 16. Holm, T. A. Engineered Masonry With High Strength Lightweight Concrete Masonry Units. Concrete Facts, Vol. 17, No. 2, 1972. 17. Specification for Masonry Structures, ACI 530.1/ASCE 6/TMS 602. Reported by the Masonry Standards Joint Committee, 2002 and 2005.

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ALL-WEATHER CONCRETE MASONRY CONSTRUCTION Keywords: cold weather construction, construction techniques, grout, hot weather construction, mortar, rain, snow, storage of materials, wet weather construction, windy weather construction INTRODUCTION Masonry construction can continue during hot, cold, and wet weather conditions. The ability to continue masonry construction in adverse weather conditions requires consideration of how environmental conditions may affect the quality of the finished masonry. In some cases, environmental conditions may warrant the use of special construction procedures to ensure that the masonry work is not adversely affected. One of the prerequisites of successful all-weather construction is advance knowledge of local conditions. Work stoppage may be justified if a short period of very cold or very hot weather is anticipated. The best source for this type of information is the U.S. Weather Bureau, Environmental Science Services Administration (ESSA) of the U.S. Department of Commerce which can be accessed at their web site http://www.ncdc.noaa.gov. In the following discussion, ambient temperature refers to the surrounding jobsite temperature when the preparation activities and construction are in progress. Similarly the mean daily temperature is the average of the hourly temperatures forecast by the local weather bureau over a 24 hour period following the onset of construction. Minimum daily temperature is the lowest temperature expected during the period. Temperatures between 40 and 90oF (4.4 and 32.2oC) are considered “normal” temperatures for masonry construction and therefore do not require special procedures or protection protocols. COLD WEATHER CONSTRUCTION When ambient temperatures fall below 40oF (4.4oC), the Specification for Masonry Structures (ref. 3) requires consideration of special construction procedures to help ensure the final construction is not adversely affected. Similarly when the minimum daily temperature for grouted masonry or the mean temperature for ungrouted masonry falls below 40oF (4.4oC) during the first 48 or 24 hours after construction respectively, special protection considerations are required.

TEK 3-1C Construction

(2002)

Mortar and Grout Performance Hydration and strength development in mortar and grout generally occurs at temperatures above 40oF (4.4oC) and only when sufficient water is available. However, masonry construction may proceed when temperatures are below 40oF (4.4oC) provided cold weather construction and protection requirements of reference 3 are followed. Mortars and grouts mixed at low temperatures have longer setting and hardening times, and lower early strength than those mixed at normal temperatures. However, mortars and grouts produced with heated materials exhibit performance characteristics identical to those produced during warm weather. Effects of Freezing The initial water content of mortar can be a significant contributing factor to the resulting properties and performance of mortar, affecting workability, bond, compressive strength, and susceptibility to freezing. Research has shown a resulting disruptive expansion effect on the cement-aggregate matrix when fresh mortars with water contents in excess of 8 %mortar are frozen (ref. 2). This disruptive effect increases as the water content increases. Therefore, mortar should not be allowed to freeze until the mortar water content is reduced from the initial 11% to 16% range to a value below 6%. Dry concrete masonry units have a demonstrated capacity to achieve this moisture reduction in a relatively short time. It is for this reason that the specification requires protection from freezing of mortar for only the first 24 hours (ref. 3). Grout is a close relative of mortar in composition and performance characteristics. During cold weather, however, more attention must be directed toward the protection of grout because of the higher water content and resulting disruptive expansion that can occur from freezing of that water. Therefore, grouted masonry needs to be protected for longer periods to allow the water content to be dissipated. Cement During cold weather masonry construction, Type III, highearly strength portland cement should be considered in lieu of Type I portland cement in mortar or grout to accelerate setting. The acceleration not only reduces the curing time but generates more heat which is beneficial in cold weather. 44

TEK 3-1C © 2002 National Concrete Masonry Association (replaces TEK 3-1B)

Admixtures The purpose of an accelerating type of admixture is to hasten the hydration of the portland cement in mortar or grout. However, admixtures containing chlorides in excess of 0.2% chloride ions are not permitted to be used in mortar (ref. 3) due to corrosion of embedded metals and contribution to efflorescence. While specifically not addressed by the Specification, the use of chloride admixtures in grout is generally discouraged. Noncloride accelerators are available but they must be used in addition to cold weather procedures and not as a replacement for them. Antifreezes are not recommended for use in mortars and are prohibited for use in grouts. Material Storage Construction materials should be protected from water by covering. Bagged materials and masonry units should be protected

from precipitation and ground water by storage on pallets or other acceptable means. Coverings for materials include tarpaulins, reinforced paper, polyethylene, or other water repellent sheet materials. If the weather and size of the project warrant, a shelter may be provided for the material storage and mortar mixing areas. Material Heating When the ambient temperature falls below 40°F (4.4°C) during construction, or mean daily temperature is predicted to fall below 40°F (4.4°C) during the first 24 hours following construction of ungrouted masonry, or the minimum daily temperature is predicted to fall below 40°F (4.4°C) during the first 48 hours for grouted masonry, Specification for Masonry Structures (ref. 3) requires specific construction and protection procedures to be implemented as summarized in Tables 1a and 1b. As indicated in

Table 1a—Cold Weather Masonry Construction Requirements (ref. 3) Ambient temperature o

32 to 40 F (0 to 4.4oC)

Construction requirements Do not lay masonry units having a temperature below 20oF (-6.7oC). Remove visible snow and ice on masonry units before the unit is laid in the masonry. Remove snow and ice from foundation. Heat existing foundation and masonry surfaces to receive new masonry above freezing. Heat mixing water or sand to produce mortar temperatures between 40 and 120oF (4.4 and 48.9oC). Grout materials to be 32oF (0oC) minimum. Do not heat water or aggregates above 140oF (60oC).

25 to 32oF (-3.9 to 0oC)

Same as above for mortar. Maintain mortar temperature above freezing until used in masonry. Heat grout aggregates and mixing water to produce grout temperatures between 70 and 120oF (21.1 and 48.9oC). Maintain grout temperature above 70oF (21.1oC) at time of grout placement.

20 to 25oF (-6.7 to -3.9oC)

Same as above, plus use heat masonry surfaces under construction to 40oF (4.4oC) and install wind breaks or enclosures when wind velocity exceeds 15 mph (24 km/hr). Heat masonry to a minimum of 40oF (4.4oC) prior to grouting.

20oF (-6.7oC) and below

Same as above, plus provide an enclosure for the masonry under construction and use heat sources to maintain temperatures above 32oF (0oC) within the enclosure.

Table 1b—Cold Weather Masonry Protection Requirements (ref. 3) Mean daily temperature for ungrouted masonry Minimum daily temperature for grouted masonry Protection requirements 25 to 40oF (-3.9 to 4.4oC)

Protect completed masonry from rain or snow by covering with a weather-resistive membrane for 24 hours after construction.

20 to 25oF (-6.7 to -3.9oC)

Completely cover the completed masonry with a weather-resistive insulating blanket or equal for 24 hours after construction (48 hr for grouted masonry unless only Type III portland cement used in grout).

20oF (-6.7oC) and below

Maintain masonry temperature above 32oF (0oC) for 24 hours after construction by enclosure with supplementary heat, by electric heating blankets, by infrared heat lamps, or by other acceptable methods. Extend time to 48 hours for grouted masonry unless the only cement in the grout is Type III portland cement. 45

Table 1a, the temperature of dry masonry units may be as low as 20oF (-6.7oC) at the time of placement. However, wet frozen masonry units should be thawed before placement in the masonry. Also, even when the temperature of dry units approaches the 20oF (-6.7oC) threshold, it may be advantageous to heat the units for greater mason productivity. Masonry should never be placed on a snow or ice-covered surface. Movement occurring when the base thaws will cause cracks in the masonry. Furthermore, the bond between the mortar and the supporting surface will be compromised. Glass Unit Masonry For glass unit masonry, both the ambient temperature and the unit temperature must be above 40oF (4.4oC) and maintained above that temperature for the first 48 hours (ref. 3).

Additional Recommendations Store masonry materials in a shaded area. Use a water barrel as water hoses exposed to direct sunlight can result in water with highly elevated temperatures. The barrel may be filled with water from a hose, but the hot water resulting from hose inactivity should be flushed and discarded first. Additionally, mortar mixing times should be no longer than 3 to 5 minutes and smaller batches will help minimize drying time on the mortar boards. To minimize mortar surface drying, past requirements contained within Specification for Masonry Structures (ref. 3) were to not spread mortar bed joints more than 4 feet (1.2 m) ahead of masonry and to set masonry units within one minute of spreading mortar. This is no longer a requirement in the current document but the concept still merits consideration. If surface drying does occur, the mortar can often be revitalized by wetting the wall but care should be taken to avoid washout of fresh mortar joints.

HOT WEATHER CONSTRUCTION WET WEATHER CONSTRUCTION High temperatures, solar radiation, and ambient relative humidity influence the absorption characteristics of the masonry units and the setting time and drying rate for mortar. When mortar gets too hot, it may lose water so rapidly that the cement does not fully hydrate. Early surface drying of the mortar results in decreased bond strength and less durable mortar. Hot weather construction procedures involve keeping masonry materials as cool as possible and preventing excessive water loss from the mortar. Specific hot weather requirements of the Specification for Masonry Structures (ref. 3) are shown in Tables 2a and 2b.

Even when ambient temperatures are between 40 and 90°F (4.4 and 32.2°C), the presence of rain, or the likelihood of rain, should receive special consideration during masonry construction. Unless protected, masonry construction should not continue during heavy rains, as partially set or plastic mortar is susceptible to washout, which could result in reduced strength or staining of the wall. However, after approximately 8 to 24 hours of curing (depending upon environmental conditions), mortar washout is no

Table 2a—Hot Weather Masonry Preparation and Construction Requirements (ref. 3) Ambient temperature

Preparation and construction requirements

Above 100oF (37.8oC) or above 90oF (32.2oC) with a wind speed greater than 8 mph (12.9 km/hr)

Maintain sand piles in a damp, loose condition. Maintain temperature of mortar and grout below 120oF (48.9oC). Flush mixer, mortar transport container, and mortar boards with cool water before they come into contact with mortar ingredients or mortar. Maintain mortar consistency by retempering with cool water. Use mortar within 2 hours of initial mixing.

Above 115oF (46.1oC) or above 105oF (40.6oC) with a wind speed greater than 8 mph (12.9 km/hr)

Same as above, plus materials and mixing equipment are to be shaded from direct sunlight. Use cool mixing water for mortar and grout. Ice is permitted in the mixing water as long as it is melted when added to the other mortar or grout materials.

Table 2b—Hot Weather Masonry Protection Requirements (ref. 3) Mean daily temperature Above 100oF (37.8oC) or above 90oF (32.2oC) with a wind speed greater than 8 mph (12.9 km/hr)

Protection requirements Fog spray all newly constructed masonry until damp, at least three times a day until the masonry is three days old.

46

longer of concern. Further, the wetting of masonry by rainwater provides beneficial curing conditions for the mortar (ref. 2). When rain is likely, all construction materials should be covered. Newly constructed masonry should be protected from rain by draping a weather-resistant covering over the assemblage. The cover should extend over all mortar that is susceptible to washout. Recommended Maximum Unit Moisture Content When the moisture content of a concrete masonry unit is elevated to excessive levels due to wetting by rain or other sources, several deleterious consequences can result including increased shrinkage potential and possible cracking, decreased mason productivity, and decreased mortar/unit bond strength. While reinforced masonry construction does not rely on mortar/unit bond for structural capacity, this is a design consideration with unreinforced masonry. As such, the concerns associated with structural bond in reinforced masonry construction are diminished. As a means of determining if a unit has acceptable moisture content at the time of installation, the following industry recommended guidance should be used. This simple field procedure can quickly ascertain whether a concrete masonry unit has acceptable moisture content at the time of installation.

A concrete masonry unit for which 50% or more of the surface area is observed to be wet is considered to have unacceptable moisture content for placement. If less than 50% of the surface area is wet, the unit is acceptable for placement. Damp surfaces are not considered wet surfaces. For this application, a surface would be considered damp if some moisture is observed, but the surface darkens when additional free water is applied. Conversely, a surface would be considered wet if moisture is observed and the surface does not darken when free water is applied. It should be noted that these limitations on maximum permissible moisture content are not intended to apply to intermittent masonry units that are wet cut as needed for special fit. WINDY WEATHER CONSTRUCTION In addition to the effects of wind on hot and cold weather construction, the danger of excessive wind resulting in structural failure of newly constructed masonry prior to the development of strength or before the installation of supports must be considered. TEK 3-4B Bracing Concrete Masonry Walls During Construction (ref. 1) provides guidance in this regard.

REFERENCES 1. Bracing Concrete Masonry Walls During Construction, TEK 3-4B. National Concrete Masonry Association, 2000 2. Hot & Cold Weather Masonry Construction. Masonry Industry Council, 1999. 3. Specification for Masonry Structures, ACI 530.1-02/ASCE 6-02/TMS 602-02. Reported by the Masonry Standards Joint Committee, 2002.

Provided by:

NCMA and the companies disseminating this technical information disclaim any and all responsibility and liability for the accuracy and the application of the information contained in this publication.

NATIONAL CONCRETE MASONRY ASSOCIATION 13750 Sunrise Valley Drive, Herndon, Virginia 20171-3499 www.ncma.org



GROUTING CONCRETE MASONRY WALLS

TEK 3-2A Construction

Keywords: cleanouts, concrete masonry units, construction techniques, consolidation, demonstration panel, grout, grouting, lift height, pour height, puddling, reinforced concrete masonry, reinforcement INTRODUCTION Grouted concrete masonry construction offers design flexibility through the use of partially or fully grouted walls, whether plain or reinforced. The industry is experiencing fast-paced advances in grouting procedures and materials as building codes allow new opportunities to explore means and methods for constructing grouted masonry walls. Grout is a mixture of: cementitious material (usually portland cement); aggregate; enough water to cause the mixture to flow readily and without segregation into cores or cavities in the masonry; and sometimes admixtures. Grout is used to give added strength to both reinforced and unreinforced concrete masonry walls by grouting either some or all of the cores. It is also used to fill bond beams and occasionally to fill the collar joint of a multi-wythe wall. Grout may also be added to increase the wall's fire rating, acoustic effectiveness termite resistance, blast resistance, heat capacity or anchor-

age capabilities. Grout may also be used to stabilize screen walls and other landscape elements. In reinforced masonry, grout bonds the masonry units and reinforcing steel so that they act together to resist imposed loads. In partially grouted walls, grout is placed only in wall spaces containing steel reinforcement. When all cores, with or without reinforcement, are grouted, the wall is considered solidly grouted. If vertical reinforcement is spaced close together and/or there are a significant number of bond beams within the wall, it may be faster and more economical to solidly grout the wall. Specifications for grout, sampling and testing procedures, and information on admixtures are covered in Grout for Concrete Masonry (ref. 1). This TEK covers methods for laying the units, placing steel reinforcement and grouting. WALL CONSTRUCTION Figure 1 shows the basic components of a typical reinforced concrete masonry wall. When walls will be grouted, concrete masonry units must be laid up so that vertical cores are aligned to form an unobstructed, continuous series of vertical spaces within the wall.

Place mesh or other grout stop device under bond beam to confine grout or use solid bottom unit Vertical reinforcement lap and secure as required

Reinforcement in bond beams is set in place as wall is laid up

Flashing Leave this block out to serve as a cleanout until wall is laid up Drip edge Cells containing reinforcement are filled solidly with grout; vertical cells should provide a continuous cavity, substantially free of mortar droppings Place mortar on cross webs adjacent to cells which will be grouted

Figure 1—Typical Reinforced Concrete Masonry Wall Section 48 TEK 3-2A © 2005 National Concrete Masonry Association (replaces TEKs 3-2 and 3-3A)

(2005)

Head and bed joints must be filled with mortar for the full thickness of the face shell. If the wall will be partially grouted, those webs adjacent to the cores to be grouted are mortared to confine the grout flow. If the wall will be solidly grouted, the cross webs need not be mortared since the grout flows laterally, filling all spaces. In certain instances, full head joint mortaring should also be considered when solid grouting since it is unlikely that grout will fill the space between head joints that are only mortared the width of the face shell, i.e., when penetration resistance is a concern such as torm shelters and prison walls. In cases such as those, open end or open core units (see Figure 3) should be considered as there is no space between end webs with these types of units. Care should be taken to prevent excess mortar from extruding into the grout space. Mortar that projects more than 1 /2 in. (13 mm) into the grout space must be removed (ref. 3). This is because large protrusions can restrict the flow of grout, which will tend to bridge at these locations potentially causing incomplete filling of the grout space. To prevent bridging, grout slump is required to be between 8 and 11 in. (203 to 279 mm) (refs. 2, 3) at the time of placement. This slump may be adjusted under certain conditions such as hot or cold weather installation, low absorption units or other project specific conditions. Approval should be obtained before adjusting the slump outside the requirements. Using the grout demonstration panel option in Specification for Masonry Structures (ref. 3) is an excellent way to demonstrate the acceptability of an alternate grout slump. See the Grout Demonstration Panel section of this TEK for further information. At the footing, mortar bedding under the first course of block to be grouted should permit grout to come into direct contact with the foundation or bearing surface. If foundation

Vertical reinforcement, as required

dowels are present, they should align with the cores of the masonry units. If a dowel interferes with the placement of the units, it may be bent a maximum of 1 in. (25 mm) horizontally for every 6 in. (152 mm) vertically (see Figure 2). When walls will be solidly grouted, saw cutting or chipping away a portion of the web to better accommodate the dowel may also be acceptable. If there is a substantial dowel alignment problem, the project engineer must be notified. Vertical reinforcing steel may be placed before the blocks are laid, or after laying is completed. If reinforcement is placed prior to laying block, the use of open-end A or Hshaped units will allow the units to be easily placed around the reinforcing steel (see Figure 3). When reinforcement is placed after wall erection, reinforcing steel positioners or other adequate devices to hold the reinforcement in place are commonly used, but not required. However, it is required that both horizontal and vertical reinforcement be located within tolerances and secured to prevent displacement during grouting (ref. 3). Laps are made at the end of grout pours and any time the bar has to be spliced. The length of lap splices should be shown on the project drawings. On occasion there may be locations in the structure where splices are prohibited. Those locations are to be clearly marked on the drawing. Reinforcement can be spliced by either contact or noncontact splices. Noncontact lap splices may be spaced as far apart as one-fifth the required length of the lap but not more than 8 in. (203 mm) per Building Code Requirements for Masonry Structures (ref. 4). This provision accommodates construction interference during installation as well as misplaced dowels.

Open end, or "A" shaped unit

Double open end or "H" shaped unit

Grout, as required

Concrete masonry wall

Dowels may be bent up to 1 in. (25 mm) laterally per 6 in. (152 mm) vertically Concrete foundation

Figure 2—Foundation Dowel Clearance

Bond beam units

Lintel unit

Pilaster units

Open core unit

Figure 3—Concrete Masonry Units for Reinforced Construction 49

Splices are not required to be tied, however tying is often used as a means to hold bars in place. As the wall is constructed, horizontal reinforcement can be placed in bond beam or lintel units. If the wall will not be solidly grouted, the grout may be confined within the desired grout area either by using solid bottom masonry bond beam units or by placing plastic or metal screening, expanded metal lath or other approved material in the horizontal bed joint before laying the mortar and units being used to construct the bond beam. Roofing felt or materials that break the bond between the masonry units and mortar should not be used for grout stops. CONCRETE MASONRY UNITS AND REINFORCING BARS Standard two-core concrete masonry units can be effectively reinforced when lap splices are not long, since the mason must lift the units over any vertical reinforcing bars that extend above the previously installed masonry. The concrete masonry units illustrated in Figure 3 are examples of shapes that have been developed specifically to accommodate reinforcement. Open-ended units allow the units to be placed

2 ft 8 in. (813 mm) pour and 2 ft 8 in. (813 mm) lift

5 ft (1.5 m) pour and 5 ft (1.5 m) lift

around reinforcing bars. This eliminates the need to thread units over the top of the reinforcing bar. Horizontal reinforcement in concrete masonry walls can be accommodated either by saw-cutting webs out of a standard unit or by using bond beam units. Bond beam units are manufactured with either reduced webs or with “knock-out” webs, which are removed prior to placement in the wall. Pilaster and column units are used to accommodate a wallcolumn or wall-pilaster interface, allowing space for vertical reinforcement and ties, if necessary, in the hollow center. Concrete masonry units should meet applicable ASTM standards and should typically be stored on pallets to prevent excessive dirt and water from contaminating the units. The units may also need to be covered to protect them from rain and snow. The primary structural reinforcement used in concrete masonry is deformed steel bars. Reinforcing bars must be of the specified diameter, type and grade to assure compliance with the contract documents. See Steel Reinforcement for Concrete Masonry, TEK 12-4C for more information (ref. 6). Shop drawings may be required before installation can begin. Light rust, mill scale or a combination of both need not be removed from the reinforcement. Mud, oil, heavy rust and

2 ft 8 in. (813 mm) lift

5 ft (1.5 m) lift 12 ft 8 in. (3.9 m) pour

Lap

5 ft (1.5 m) pour and 5 ft (1.5 m) lift

Lap

Grouting without cleanouts: (Low-lift) No cleanouts required Wall built in 3 stages Bars spliced at pour height Three grout lifts

5 ft (1.5 m) lift Lap

Cleanout

12 ft 8 in. (3.9 m) pour and 12 ft 8 in (3.9 m) lift

Lap Cleanout

Grouting with cleanouts: Grouting with cleanouts per (High-lift) MSJC (2005) or grout demonstration panel: Cleanouts required Cleanouts required Wall built full height Wall built full height Bars installed full length (no splicing) Bars installed full length (no splicing) Three grout lifts One grout lift

Figure 4—Comparison of Grouting Methods for a 12 ft-8 in. (3,860 mm) High Concrete Masonry Wall 50

other materials which adversely affect bond must be removed however. The dimensions and weights (including heights of deformations) of a cleaned bar cannot be less than those required by the ASTM specification. GROUT PLACEMENT To understand grout placement, the difference between a grout lift and a grout pour needs to be understood. A lift is the amount of grout placed in a single continuous operation. A pour is the entire height of masonry to be grouted prior to the construction of additional masonry. A pour may be composed of one lift or a number of successively placed grout lifts, as illustrated in Figure 4. Historically, only two grout placement procedures have been in general use: (l) where the wall is constructed to pour heights up to 5 ft (1,520 mm) without cleanouts—generally termed “low lift grouting;” and (2) where the wall is constructed to a maximum pour height of 24 ft (7,320 mm) with required cleanouts and lifts are placed in increments of 5 ft (1,520 mm)—generally termed “high lift grouting.” With the advent of the 2002 Specification for Masonry Structures (ref. 5), a third option became available – grout demonstration panels. The 2005 Specification for Masonry Structures (ref. 3) offers an additional option: to increase the grout lift height to 12 ft-8 in. (3,860 mm) under the following conditions: 1. the masonry has cured for at least 4 hours, 2. grout slump is maintained between 10 and 11 in. (245 and 279 mm), and 3. no intermediate reinforced bond beams are placed between the top and the bottom of the pour height. Through the use of a grout demonstration panel, lift heights in excess of the 12 ft-8 in. (3,860 mm) limitation may be permitted if the results of the demonstration show that the completed grout installation is not adversely affected. Written approval is also required. These advances permit more efficient installation and construction options for grouted concrete masonry walls (see Figure 4). Grouting Without Cleanouts—"Low-Lift Grouting” Grout installation without cleanouts is sometimes called low-lift grouting. While the term is not found in codes or standards, it is common industry language to describe the process of constructing walls in shorter segments, without the requirements for cleanout openings, special concrete block shapes or equipment. The wall is built to scaffold height or to a bond beam course, to a maximum of 5 ft (1,520 mm). Steel reinforcing bars and other embedded items are then placed in the designated locations and the cells are grouted. Although not a code requirement, it is considered good practice (for all lifts except the final) to stop the level of the grout being placed approximately 1 in. (25 mm) below the top bed joint to help provide some mechanical keying action and water penetration resistance. Further, this is needed only when a cold joint is formed between the lifts and only in areas that will be receiving additional grout. Steel reinforcement should

project above the top of the pour for sufficient height to provide for the minimum required lap splice, except at the top of the finished wall. Grout is to be placed within 11/2 hours from the initial introduction of water and prior to initial set (ref. 3). Care should be taken to minimize grout splatter on reinforcement, on finished masonry unit faces or into cores not immediately being grouted. Small amounts of grout can be placed by hand with buckets. Larger quantities should be placed by grout pumps, grout buckets equipped with chutes or other mechanical means designed to move large volumes of grout without segregation. Grout must be consolidated either by vibration or puddling immediately after placement to help ensure complete filling of the grout space. Puddling is allowed for grout pours of 12 in. (305 mm) or less. For higher pour heights, mechanical vibration is required and reconsolidation is also required. See the section titled Consolidation and Reconsolidation in this TEK. Grouting With Cleanouts—"High-Lift Grouting” Many times it is advantageous to build the masonry wall to full height before grouting rather than building it in 5 ft (1,520 mm) increments as described above. With the installation of cleanouts this can be done. Typically called high-lift grouting within the industry, grouting with cleanouts permits the wall to be laid up to story height or to the maximum pour height shown in Table 1 prior to the installation of reinforcement and grout. (Note that in Table 1, the maximum area of vertical reinforcement does not include the area at lap splices.) High lift grouting offers certain advantages, especially on larger projects. One advantage is that a larger volume of grout can be placed at one time, thereby increasing the overall speed of construction. A Table 1—Grout Space Requirements (ref. 3) Grout Max. grout type1 pour height, ft (m) Fine Fine Fine Fine Coarse Coarse Coarse Coarse 1 2 3

4

1 (0.30) 5 (1.52) 12 (3.66) 24 (7.32) 1 (0.30) 5 (1.52) 12 (3.66) 24 (7.32)

Min. width of grout space 2,3, in. (mm) ¾ (19.1) 2 (50.8) 2½ (63.5) 3 (76.2) 1½ (38.1) 2 (50.8) 2½ (63.5) 3 (76.2)

Min. grout space dimensions for grouting cells of hollow units 3,4 in. x in. (mm x mm) 1½ x 2 (38.1 x 50.8) 2 x 3 (50.8 x 76.2) 2½ x 3 (63.5 x 76.2) 3 x 3 (76.2 x 76.2) 1½ x 3 (38.1 x 76.2) 2½ x 3 (63.5 x 76.2) 3 x 3 (76.2 x 76.2) 3 x 4 (76.2 x 102)

Fine and coarse grouts are defined in ASTM C 476 (ref. 2). For grouting between masonry wythes. Grout space dimension is the clear dimension between any masonry protrusion and shall be increased by the diameters of the horizontal bars within the cross section of the grout space. Area of vertical reinforcement shall not exceed 6 percent of the area of the grout space. 51

second advantage is that high-lift grouting can permit constructing masonry to the full story height before placing vertical reinforcement and grout. Less reinforcement is used for splices and the location of the reinforcement can be easily checked by the inspector prior to grouting. Bracing may be required during construction. See Bracing Concrete Masonry Walls During Construction, TEK 3-4B (ref. 7) for further information. Cleanout openings must be made in the face shells of the bottom course of units at the location of the grout pour. The openings must be large enough to allow debris to be removed from the space to be grouted. For example, Specification for Masonry Structures (ref. 3) requires a minimum opening dimension of 3 in. (76 mm). Cleanouts must be located at the bottom of all cores containing dowels or vertical reinforcement and at a maximum of 32 in. (813 mm) on center (horizontal measurement) for solidly grouted walls. Face shells are removed either by cutting or use of special scored units which permit easy removal of part of the face shell for cleanout openings (see Figure 5). When the cleanout opening is to be exposed in the finished wall, it may be desirable to remove the entire face shell of the unit, so that it may be replaced in whole to better conceal the opening. At flashing where reduced thickness units are used as shown in Figure 1, the exterior unit can be left out until after the masonry wall is laid up. Then after cleaning the cell, the unit is mortared in which allowed enough time to gain enough strength to prevent blowout prior to placing the grout. Proper preparation of the grout space before grouting is very important. After laying masonry units, mortar droppings and projections larger than 1/2 in. (13 mm) must be removed from the masonry walls, reinforcement and foundation or bearing surface. Debris may be removed using an air hose or by sweeping out through the cleanouts. The grout spaces should be checked by the inspector for cleanliness and reinforcement position before the cleanouts are closed. Cleanout openings may be sealed by mortaring the original face shell or section of face shell, or by blocking the openings to allow grouting to the finish plane of the wall. Face shell plugs should be adequately braced to resist fluid grout pressure. It may be advisable to delay grouting until the mortar has

been allowed to cure, in order to prevent horizontal movement (blowout) of the wall during grouting. When using the increased grout lift height provided for in Article 3.5 D of Specification for Masonry Structures (ref 3), the masonry is required to cure for a minimum of 4 hours prior to grouting for this reason. Consolidation and Reconsolidation An important factor mentioned in both grouting procedures is consolidation. Consolidation eliminates voids, helping to ensure complete grout fill and good bond in the masonry system. As the water from the grout mixture is absorbed into the masonry, small voids may form and the grout column may settle. Reconsolidation acts to remove these small voids and should generally be done between 3 and 10 minutes after grout placement. The timing depends on the water absorption rate, which varies with such factors as temperature, absorptive properties of the masonry units and the presence of water repellent admixtures in the units. It is important to reconsolidate after the initial absorption has taken place and before the grout loses its plasticity. If conditions permit and grout pours are so timed, consolidation of a lift and reconsolidation of the lift below may be done at the same time by extending the vibrator through the top lift and into the one below. The top lift is reconsolidated after the required waiting period and then filled with grout to replace any void left by settlement. A mechanical vibrator is normally used for consolidation and reconsolidation—generally low velocity with a 3/4 in. to 1 in. (19 to 25 mm) head. This “pencil head” vibrator is activated for a few seconds in each grouted cell. Although not addressed by the code, recent research (ref. 8) has demonstrated adequate consolidation by vibrating the top 8 ft (2,440 mm) of a grout lift, relying on head pressure to consolidate the grout below. The vibrator should be withdrawn slowly enough while on to allow the grout to close up the space that was occupied by the vibrator. When double openend units are used, one cell is considered to be formed by the two open ends placed together. When grouting between wythes, the vibrator is placed at points spaced 12 to 16 in. (305 to 406 mm) apart. Excess vibration may blow out the face shells or may separate wythes when grouting between wythes and can also cause grout segregation. GROUT DEMONSTRATION PANEL

Figure 5—Unit Scored to Permit Removal of Part of Face Shell for Cleanout

Specification for Masonry Structures (ref. 3) contains a provision for “alternate grout placement” procedures when means and methods other than those prescribed in the document are proposed. The most common of these include increases in lift height, reduced or increased grout slumps, minimization of reconsolidation, puddling and innovative consolidation techniques. Grout demonstration panels have been used to allow placement of a significant amount of a relatively new product called self-consolidating grout to be used in many parts of the country with outstanding results. 52

Research has demonstrated comparable or superior performance when compared with consolidated and reconsolidated conventional grout in regard to reduction of voids, compressive strength and bond to masonry face shells. Construction and approval of a grout demonstration panel using the proposed grouting procedures, construction techniques and grout space geometry is required. With the advent of self-consolidating grouts and other innovative consolidation techniques, this provision of the Specification has been very useful in demonstrating the effectiveness of alternate grouting procedures to the architect/engineer and building official. COLD WEATHER PROTECTION Protection is required when the minimum daily temperature during construction of grouted masonry is expected to fall below 40oF (4.4oC). Grouted masonry requires special consideration because of the higher water content and potential disruptive expansion that can occur if that water freezes. Therefore, grouted masonry requires protection for longer periods than ungrouted masonry to allow the water to dissipate. For more detailed information on cold, hot, and wet weather protection, see All-Weather Concrete Masonry Construction, TEK 3-1C (ref. 9).

REFERENCES 1. Grout for Concrete Masonry, TEK 9-4. National Concrete Masonry Association, 2002. 2. Standard Specification for Grout for Masonry, ASTM C 476-02, ASTM International, 2005. 3. Specification for Masonry Structures, ACI 530.1-05/ ASCE 6-05/TMS 602-05. Reported by the Masonry Standards Joint Committee, 2005. 4. Building Code Requirements for Masonry Structures, ACI 530-05/ASCE 5-05/TMS 402-05. Reported by the Masonry Standards Joint Committee, 2005. 5. Specification for Masonry Structures, ACI 530.1-02/ ASCE 6-02/TMS 602-02. Reported by the Masonry Standards Joint Committee, 2002. 6. Steel Reinforcement for Concrete Masonry, TEK 12-4C. National Concrete Masonry Association, 2002. 7. Bracing Concrete Masonry Walls During Construction, TEK 3-4B. National Concrete Masonry Association, 2002. 8. Investigation of Alternative Grouting Procedures in Concrete Masonry Construction Through Physical Evaluation and Quality Assessment, MR 25. National Concrete Masonry Association, 2004. 9. All-Weather Concrete Masonry Construction, TEK 3-1C. National Concrete Masonry Association, 2002.

Provided by:



An

information

series

from

the

national

authority

on

concrete

masonry

technology

Prepared in cooperation with the International Masonry Institute

HYBRID CONCRETE MASONRY TEK 3-3B CONSTRUCTION DETAILS Construction (2009) INTRODUCTION Hybrid masonry is a structural system that utilizes reinforced masonry walls with a framed structure. While the frame can be constructed of reinforced concrete or structural steel, the discussion here includes steel frames with reinforced concrete masonry walls. The reinforced masonry infill participates structurally with the frame and provides strength and stiffness to the system. It can be used in single wythe or cavity wall construction provided the connections and joints are protected against water penetration and corrosion. The hybrid walls are constructed within the plane of the framing. Depending on the type of hybrid wall used, the framing supports some or all of the masonry wall weight. Hybrid masonry/frame structures were first proposed in 2006 (ref. 1). There are several reasons for its development but one primary reason is to simplify the construction of framed buildings with masonry infill. While many designers prefer masonry infill walls as the backup for veneers in framed buildings, there is often a conflict created when structural engineers design steel bracing for the frame which interferes with the masonry infill. This leads to detailing and construction interferences trying to fit masonry around braces. One solution is to eliminate the steel bracing and use reinforced masonry infill as the shear wall bracing to create a hybrid structural system. The concept of using masonry infill to resist lateral forces is not new; having been used successfully throughout the world in different forms. While common worldwide, U.S. based codes and standards have lagged behind in the establishment of standardized means of designing masonry infill. The hybrid masonry system outlined in this TEK is a unique method of utilizing masonry infill to resist

Related TEK: 14-9A NCMA TEK 3-3B

lateral forces. The novelty of the hybrid masonry design approach relative to other more established infill design procedures is in the connection detailing between the masonry and steel frame, which offers multiple alternative means of transferring loads into the masonry—or isolating the masonry infill from the frame. Prior to implementing the design procedures outlined in this TEK, users are strongly urged to become familiar with the hybrid masonry concept, its modeling assumptions, and its limitations particularly in the way in which inelastic loads are distributed during earthquakes throughout the masonry and frame system. This system, or design methods, should not be used in Seismic Design Category D and above until further studies and tests have been performed; and additional design guidance is outlined in adopted codes and standards. CLASSIFICATION OF WALLS There are three hybrid wall types, Type I, Type II and Type III. The masonry walls are constructed within the plane of the framing. The classification is dependent upon the degree of confinement of the masonry within the frame. Type I walls have soft joints (gaps that allow lateral drift at the columns or vertical deflection at the top) at the columns and the top of the wall. The framing supports the full weight of the masonry walls and other gravity loads. Type II walls have soft joints at the columns and are built tight at the top of the wall. Type III walls are built tight at the columns and the top of the wall. For Type II and III walls, the masonry walls share the support of the vertical loads, including the wall weight, with the framing.

Keywords: frame structures, infill, hybrid, shear walls, tie-down, reinforced masonry 1

54

CONSTRUCTION Type I Hybrid Walls Practically speaking, the concept of Type I walls is that the masonry wall is a nonloadbearing shear wall built within the frame which also supports out-ofplane loads (see Figure 1). The details closely match those for current cavity wall construction where the infill masonry is within the plane of the frame, except that the vertical reinforcement must be welded to the perimeter framing at supported floors. Since the walls are generally designed to span vertically, the walls may not have to be anchored to the columns. The engineer’s design should reflect whether anchors are required but only for out-of-plane loads. The masonry does have to be isolated from the columns so the columns do not transmit loads to the walls when the frame drifts. In multi-story buildings, each wall is built independently. Walls can be constructed on multiple floors simultaneously. Because the steel framing is supporting the entire wall weight, Type 1 walls are more economical for lower rise buildings. It is possible with Type 1 walls to position the walls outside the framing so they are foundation supported as in caged construction (ref. 1), providing a more economical design for the framing. Type II Hybrid Walls With Type ll walls, the masonry wall is essentially a loadbearing shear wall built within the frame: it supports both gravity and out-of-plane loads (see Fig. 1). There are two options: Type IIa and Type IIb. The engineer must indicate which will be used. For Type IIa walls, the vertical reinforcement (dowels) must be welded to the perimeter framing to transfer tension tiedown forces into the frame. The vertical dowels also transfer shear. For Type IIb walls, vertical reinforcement only needs to be doweled to the concrete slab to transfer shear forces because tie-down is not required. This simplifies the construction of multi-story buildings. The top of the masonry wall must bear tight to the framing. Options include grouting the top course, using solid units, or casting the top of the wall. The top connectors must extend down from the framing to overlap with the vertical wall reinforcement. Since the walls generally span vertically, the engineer must decide whether column anchors are needed similar to Type I walls. These anchors only need to transmit out-of-plane loads. The design must take into account the construction phasing. In multi-story buildings, each wall may be structurally dependent on a wall from the floor below which is very similar to a loadbearing masonry building.

Type III Hybrid Walls This wall type is fully confined within the framing—at beams and columns. Currently, there are no standards in the United States that govern Type III design. Standards are under development and research is underway to help determine structural and construction requirements. Therefore, no details are provided at this time. DETAILS Sample construction details were developed in conjunction with the National Concrete Masonry Association, International Masonry Institute (IMI), and David Biggs. They are hosted on the NCMA web site at www.ncma.org and the IMI web site at www. imiweb.org. Alternate details for hybrid construction are continually under development and will be posted on the web sites. There are several key details that must be considered, including: the wall base, the top of the wall, at columns, and parapets.

Type I Hybrid Wall

Type II Hybrid Wall Figure 1—Hybrid Wall Types I and II

2

NCMA TEK 3-3B

55

Base of Wall As previously noted for Type I and Type IIa walls, vertical reinforcement must be anchored to either foundation or frame to provide tension-tie downs for the structure. Figure 2 shows the reinforcement anchored to the foundation with a tension lap splice, and also shows the reinforcement anchored at a floor level and tension lap spliced. For Type IIb walls, the vertical reinforcement does not have to be anchored for tension forces because it only transfers shear forces. Figure 3 shows the reinforcement anchored to the foundation. Figure 4 shows the reinforcement anchored at a floor level. The designer must determine if the dowel can be effectively anchored to the slab for shear or if it must be welded to the framing as shown for Type I and Type IIa walls.

connectors at the top of the wall. Since the top course could be a solid unit, the connector should extend down to a solid grouted bond beam. Top of wall construction raises the most concern by designers. Constructability testing by masons has been successfully performed. The design concept for the connectors is: 1. Determine the out-of-plane loads to the wall top. 2. Design the top bond beam to span horizontally between connectors. Connector spacing is a designer's choice but is generally between 2 and 4 ft (6.09 and 1.22 m) o. c. 3. Using the in-plane loading, analyze the connector and design the bolts. 4. If the design does not work, repeat using a smaller connector spacing.

Top of Wall For all wall types, the top of the wall must be anchored to transfer in-plane shear loads from the framing to the wall. It also accommodates out-of-plane forces. This is accomplished by a connector. Figures 5 and 5A show an example with bent plates and slotted holes. For Type I walls, the gap at the top of the wall must allow for the framing to deflect without bearing on the wall or loading the bolts. For Type II walls, the gap is filled tight so the framing bears on the wall. The vertical reinforcement must overlap with the

Figure 3—Type IIb Foundation Detail

Figure 2—Type I and IIa Foundation and Floor Detail NCMA TEK 3-3B

Figure 4—Type IIb Floor Detail 3

56

Note: For Type I walls, provide soft joint (gap to allow for movement. For Type II walls, fill gap tight.

Figure 5—Top of Wall Details 4

NCMA TEK 3-3B

57

Figure 5—Top of Wall Details (continued)

Figure 5A—Connector Plate Detail NCMA TEK 3-3B

5

58

Figure 6—Column Details

Option 1 Figure 7—Parapet Details 6

NCMA TEK 3-3B

59

Option 2

Option 3 Figure 7—Parapet Details (continued) NCMA TEK 3-3B

7

60

The steel framing is affected by out-of-plane load transfer to the beam's bottom flange. Beam analysis and flange bracing concerns for the steel are identical to those for any infill wall. Column For Type I and IIa walls, the wall must be kept separated from the columns so that when the frame drifts it does not bear on the wall. Lightweight anchors can be used to support out-of-plane loads if desired. Figure 6 shows a possible anchor. Parapet Parapets can be constructed by cantilevering off the roof framing. Details vary depending on the framing used but are similar to Figure 2. Figure 7 shows three variations for: concrete slab, wide flange framing, and bar joist framing. There is a plate on the beam's top flange for the bar joist and wide flange framing options. QUALITY ASSURANCE

of the quality assurance plan. Besides verifying the vertical reinforcement is properly installed as required by Building Code Requirements for Masonry Structures (ref. 2), the connector must be checked as well. If Type I walls are used, the bolts from the connector to the wall must allow for vertical deflection of the framing without loading the wall. CONCLUSIONS Hybrid masonry offers many benefits and complements framed construction. By using the masonry as a structural shear wall, the constructability of the masonry with the frames is improved, lateral stiffness is increased, redundancy is improved, and opportunities for improved construction cost are created. For now, Type I and Type II hybrid systems can be designed and constructed in the United States using existing codes and standards. Criteria for Type III hybrid systems are under development. Design issues for hybrid walls are discussed in TEK 14-9A and IMI Tech Brief 02.13.01 (refs. 3, 4).

Special inspections should be an essential aspect REFERENCES 1. Biggs, D.T., Hybrid Masonry Structures, Proceedings of the Tenth North American Masonry Conference. The Masonry Society, June 2007. 2. Building Code Requirements for Masonry Structures, ACI 530-08/ASCE 5-08/TMS 402-08. The Masonry Society, 2008. 3. Hybrid Concrete Masonry Design, TEK 14-9A. National Concrete Masonry Association, 2009. 4. Hybrid Masonry Design, IMI Technology Brief 02.13.01. International Masonry Institute, 2009.



Provided by:

8

NCMA TEK 3-3B

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BRACING CONCRETE MASONRY WALLS DURING CONSTRUCTION

TEK 3-4B Construction

(2005)

Keywords: backfilling, basement walls, bracing walls, construction loads, lateral loads, plain concrete masonry, restricted zone, unreinforced concrete masonry, wind loads Figure 1. When the wind speeds exceed those allowed during the Initial and Intermediate Periods, there is a chance that the masonry wall could fail and the Restricted Zone must be evacuated in order to ensure life safety.

INTRODUCTION Various codes and regulations relating to buildings and structures place responsibility on the erecting contractor for providing a reasonable level of life safety for workers during construction. Until the recent development of the Standard Practice for Bracing Masonry Walls During Construction (ref. 3) by the Council for Masonry Wall Bracing, there were no uniform guidelines for masonry wall stability. The Standard only addresses strategies to resist the lateral loading effects of wind during construction. When other lateral loads such as impact, seismic, scaffolding, and lateral earth pressure are present, they need to be considered and evaluated separately. A section is provided at the end of this TEK regarding bracing and support of basement walls during backfilling operations.

Initial Period The Initial Period is the time frame during which the masonry is being laid above its base or highest line of bracing, limited to a maximum of one working day. During this period, the mortar is assumed to have no strength and wall stability is accomplished from its self weight only. Based on this assumption and a wind speed limit of 20 mph (32.2 km/hr), walls can be built to the height shown in Table 1 without bracing during the Initial Period. If wind speeds exceed 20 mph (32.2 km/hr) during the Initial Period, work on the wall must cease

WALLS SUBJECT TO WIND FORCES Recognizing that it may be impracticable to prevent the collapse of a masonry wall during construction when subjected to extreme loading conditions and that life safety is the primary concern, the Standard includes a procedure whereby the wall and the area around it is evacuated at prescribed wind speeds. Wind speeds as defined in the Standard are five-second gusts measured at the job site. The critical wind speed resulting in evacuation is dependent on the age of the wall being constructed and involves three new terms. They are “Restricted Zone,” “Initial Period,” and “Intermediate Period.” Restricted Zone The Restricted Zone is the area on each side of a wall equal to the length of the wall and extending a distance perpendicular to the wall equal to the height of the constructed wall plus 4 ft. (1.22 m), as shown in

Restricted zone

h ngt Le

Height

He igh t+

4f

t (1 .22

Restricted zone m)

He igh t+

4f t (1 .22

m)

Le

h ngt

Figure 1—Restricted Zone for Masonry Walls 62

TEK 3-4B © 2005 National Concrete Masonry Association (replaces TEK 3-4A)

scaffolding and evacuate the restricted zone. Table 3 lists bracing points determined by the bracing method previously described and Figure 2 shows a wood brace detail for support Density of Masonry Units, γ , lb/ft3 (kg/m3) Nominal wall Lightweight Medium Weight Normal Weight heights up to 14'-4" (4.37 m) maximum. Proprithickness, Units Units3 Units etary pipe bracing systems and cable systems in (mm) 95 < γ < 105 105 < γ < 115 115 < γ < 125 125 < γ are also available for all heights shown in Table (1522<γ<1682) (1682<γ<1842) (1842<γ<2002) (2002< γ) 3 and are detailed in the Standard. Provisions 4 (102) 8.0(2.44) 8.0(2.44) 8.0(2.44) 8.0(2.44) also are included in the Standard for strength 6(152) 8.0(2.44) 8.0(2.44) 8.0(2.44) 8.1(2.47) design methods. 8(203) 10.8(3.29) 12.0(3.66) 13.1(3.99) 14.2(4.33) Research has shown that properly designed 10(254) 17.0(5.18) 18.8(5.73) 20.0(6.10) 22.0(6.71) and constructed reinforcement splices can 12(305) 23.2(7.07) 25.7(7.84) 28.1(8.56) 30.6(9.33) achieve up to 75% of the specified yield stress Footnotes: of the reinforcing steel at 12 hours and 100% at 1. Height of walls above grade or highest line of lateral support 24 hours (ref. 3). Therefore, the Standard al2. Adapted from ref. 3. lows the full capacity of splices after grout has 3. For medium weight units, use 105 < γ < 115 (1682 < γ < 1842) category unless it is known that units are 115 < γ < 125 (1842 < γ < 2002). been in place 24 hours. Alternatively, the full splice capacity can be used after only 12 hours and the Restricted Zone on both sides of the wall must be if the design lap length is increased by 1/3 (to 40 in. (1016 evacuated. Evacuation for walls up to 8 ft (2.44 m) above mm) for No. 5 (No. 16M) bars). grade is not necessary until wind speeds reach 35 mph (56.3 Connections to masonry can be designed using the prekm/hr) in keeping with a long-standing OSHA requirement. viously quantified reduced masonry strengths and design formulas included in the Standard. As an alternate, restricted working loads for post-drilled anchors as reported in the Intermediate Period manufacturer's literature may be used. The Intermediate Period is the time following the Initial Period but before the wall is connected to the elements that provide its final lateral stability. The design wind speed is 40 Design Example mph (64.4 km/hr) 5 second gust for brace design. When the Determine the bracing requirements for a 24 ft (7.32 m) tall wind speed exceeds 35 mph (56.3 km/hr), the Restricted wall constructed with 8 in. (203 mm) concrete masonry Zone must be evacuated. The difference of 5 mph (8.0 km/hr) having a density of 110 lb/ft3 (1762 kg/m3) and reinforceis to allow workers time to evacuate the area. ment of No. 5 at 32 in. (No. 16M at 813 mm) on center using During the Intermediate Period, the masonry is assumed 30 in. (762 mm) splice lengths. Mortar is masonry cement to have one half of its design compressive strength and plain Type S, control joints are spaced at 24'-8" (7.52 m), and masonry allowable flexural stresses are taken as two-thirds flashing is at the base of the wall only. of the design value given in the Masonry Standards Joint Committee’s Building Code Requirements for Masonry Initial Period Structures (ref. 1). The masonry structural capacity then can From Table 1: be designed using these reduced values in accordance with Maximum unsupported height = 12'-0" (3.66 m). (These the provisions of the Code. initial period provisions apply to all of the options that The Standard allows for several methods of providing an follow). acceptable level of life safety for masons and others working on the construction site. They are: 1) an early warning and Intermediate Period - Unbraced Option evacuation program, 2) bracing to a design wind speed of 40 From Table 2: mph (64.4 kph), 5 second gust and evacuating if the wind Alternate 1: Evacuation wind speed of 15 mph (24.1 kph) speed exceeds 35 mph (56.3 kph), 5 second gust, and 3) Unreinforced wall: alternative bracing designs and methods approved by a regisMaximum height, unbonded = 12'-8" (3.86 m) tered professional engineer if supported by data representing Maximum height, bonded = 13'-4" (4.06 m) field conditions. Reinforced wall: Table 2 lists maximum unbraced wall heights when early Maximum height, bonded or unbonded = 26'-0" warning with an evacuation program is implemented. Maxi(7.92 m) mum allowable heights are provided for evacuation for 5 second gust wind speeds of 15 mph (24.1 kph), 25 mph (40.2 Strategy: Since reinforcement is No. 5 at 32 in. (No. 16M at 813 kph), and 35 mph (56.3 kph). The Standard also provides mm) o.c., the table values for No. 5 at 48 in. (16M at 1.22 additional tables for 20 and 30 mph (32.2 and 48.3 kph) which m) o.c. can conservatively be used. Build the wall to a are not presented in this TEK. Design wind speeds for the height of 12'-0" (3.66 m) the first day (Initial Period). unbraced heights in Table 2 are 5 mph greater than the The maximum unbonded height during the Intermediate evacuation speed to allow time for the masons to get off the Table 1—Maximum Unbraced Height1 of Ungrouted Hollow Concrete Masonry Walls During the Initial Period2, ft (m)

63

Table 2—Intermediate Period Maximum Unbraced Heights, ft (m)1,2 (adapted from ref. 3) Evacuation Wind Speed3 15 mph (24.1 kph) Bracing Condition

PCL & MRC4 M/S

N

25 mph (40.2 kph)

MC 5 M/S

N

PCL & MRC4 M/S

N

35 mph (56.3 kph)

MC 5 M/S

PCL & MRC4

N

M/S

N

MC 5 M/S

N

Unreinforced 8 in. (203 mm) wall Unbonded6 Bonded8

6'-0" (1.83)7

12'-8" (3.66)

8'-0"

3'-4" (1.02)7

16'-0"

14'-8"

13'-4" 12'-0"

10'-0"

8'-8"

6'-8"

6'-8"

6'-0"

5'-4"

4'-8"

(4.88)

(4.47)

(4.06) (3.66)

(3.05)

(2.64) (2.44) (2.03) (2.03) (1.83) (1.63) (1.42)

Unreinforced12 in. (305 mm) wall Unbonded6 Bonded8

28'-0" (8.53)

7'-4" (2.24)7

12'-8" (3.86)

27'-4"

25'-4"

23'-8" 22'-0"

15'-4"

14'-0" 12'-8" 11'-4" 10'-8" 10'-0" 8'-8"

8'-0"

(8.33)

(7.72)

(7.21) (6.71)

(4.67)

(4.27) (3.86) (3.45) (3.25) (3.05) (2.64) (2.44)

Reinforced 8 in.(203 mm) wall9,10 Unbonded or bonded No. 5 at 10 ft (16M at 3.05 m) o.c.11

20'-8" (6.30)

16'-8" (5.08)

26'-0" (7.92)

25'-4" (7.72)

12'-0" (3.66)

Unbonded or bonded No. 5 at 4 ft (16M at 1.22 m) o.c.11

19'-4" (5.89) 9,10

Reinforced 12 in. (305 mm) wall Unbonded or bonded No. 5 at 10 ft (16M at 3.05 m) o.c.11

28'-8" (8.74)

23'-4" (7.11)

20'-0" (6.10)

33'-4" (10.2)

33'-4" (10.2)

24'-0" (7.32)

Unbonded or bonded No. 5 at 6 ft (16M at 1.22 m) o.c.11

Footnotes: 1. Maximum height above highest line of lateral support permitted without bracing at windspeed indicated. 2. These values can be applied to all hollow concrete masonry of 95 lb/ft3 (1522 kg/m3) and greater density and all solid concrete masonry. 3. Wall design wind speed is 5 mph (8.05 kph) greater than evacuation wind speed. 4. PCL indicates portland cement/lime. MRC indicates mortar cement. 5. MC indicates masonry cement mortar. 6. Assumes an unbonded condition between the wall and foundation such as at flashing. 7. Exception: Walls may extend up to a height of 8 ft (2.44 m) above the ground without bracing. 8. Assumes continuity of masonry at the base (i.e. no flashing). 9. Reinforced walls shall be considered unreinforced until grout is in place 12 hrs. 10. Reinforcement indicated is minimum vertical required and shall be continuous into the foundation. Minimum lap splice for grout between 12 and 24 hrs. old is 40 in. (1016 mm) or 30 in. (762 mm) splice length for grout 24 hrs. old and over. 11. For reinforced walls not requiring bracing, check adequacy of foundation to prevent overturning.

Period is 12'-8" (3.86 m) for this wind speed, therefore neither bracing nor grouting needs be done for the 12 ft (3.86 m) height for the intermediate period. If the wall is reinforced and grouted, it can support a total height of 26 ft (7.92 m), the top 13'-4" (4.06 m) of which can be unreinforced, bonded masonry. Therefore if the first 12 ft (3.86 m) is reinforced and grouted, the remaining 12 ft (3.86 m) could be built after 24 hours of placing the grout if the standard 30 in. (1016 mm) reinforcement splice is

used (or 12 hours with a 40 in. (762 mm) splice). The total height of 24'-0" (7.32 m) is less than the maximum of 26'-0" (7.92 m) that the reinforced section can support and the top 12'-0" (3.66 m) is less than 13'-4" maximum that unreinforced bonded masonry can support. Therefore the wall can be built in this manner without bracing. Note: This option requires early warning and evacuation when wind speeds reach 15 mph (24.1 kph) 5 second gust. This may not be practical in all areas. 64

Alternate 2: Design for an evacuation wind speed of 25 mph (40.2 kph). Unreinforced wall: Maximum height, unbonded = 8'0" (2.44 m) at ground level, 6'-0" (1.83 m) otherwise Maximum height, bonded = 8'0" (2.44 m) Reinforced wall: Maximum height, bonded or unbonded = 25'-4" (7.92 m) Strategy: Again, build the wall to a height of 12'-0" (3.66 m) the first day (Initial Period). Since the maximum unbonded height above grade during the Intermediate Period is 8'-0" (2.44 m) for this wind speed, grouting must be done the first day. The restricted zone must then be vacated for the first 24 hours after placing the grout when using the standard 30 in. (762 mm) reinforcement splice (or 12 hours for 40 in. (1016 mm) splices). After that continue building the wall up to the height of 24'-0" (7.32 m) which is less than the maximum of 25'-4"

(7.72 m). The top 12'-0" (3.66 m) of this is bonded unreinforced masonry which is more than 6'-0" (1.83 m) maximum. Therefore, it must also be grouted the same day and the restricted zone vacated for the next 12 or 24 hours depending on the splice length used. Intermediate Period - Braced Option From Table 3 ( for 35 mph, 56.3 kph): Unreinforced wall: Maximum unsupported height = 3'-4" (1.02 m) Maximum height above top brace = 5'-4" (1.63 m) Maximum vertical spacing of braces = 11'-4" (3.45 m) Reinforced wall: Maximum height above top brace =10'-8" (3.25 m) Maximum vertical spacing of braces = 21'-4" (6.50 m) Strategy: Build the wall to a height of 12'-0" (3.66 m) the first day (Initial Period) and brace at a height of 11'-4" (3.45 m) by the end of

Table 3—Intermediate Period Brace Locations, ft-in. (m)1,2 35 mph (56.3 kph) Evacuation Wind Speed, 40 mph (64.4 kph) Design Wind Speed Hollow Concrete Masonry, 95 lb/ft3 (1522 kg/m3) Density, (adapted from ref. 3) PCL & MRC3 MC4 Bracing Condition M/S N M/S N Unreinforced 8" (203 mm) wall Maximum unbraced height, unbonded condition5 (i.e. at flashing)5 3'-4"6(1.02) 7 Maximum height above top brace 6'-8"(2.03) 6'-0"(1.83) 5'-4"(1.62) 4'-8"(1.42) Maximum vertical spacing between braces7 14'-0"(4.26) 12'-8"(3.85) 11'-4"(3.45) 10'-0"(3.04) Unreinforced 12" (305 mm) wall 5 Maximum unbraced height, unbonded condition (i.e. at flashing)5 7'-4"6 (2.24) 7 Maximum height above top brace 10'-8"(3.25) 10'-0"(3.04) 8'-8"(2.64) 8'-0"(2.44) Maximum vertical spacing between braces7 21'-4"(6.50) 19'-4"(5.89) 17'-4"(5.28) 16'-0"(4.88) Reinforced 8" (203 mm) wall8,9 Maximum unbraced height, unbonded condition5 and height above top brace7,11 10'-8"(3.25) Maximum vertical spacing between braces 21'-4"(6.50) 8,10 Reinforced 12" (305 mm) wall Maximum unbraced height, unbonded condition5 and height above top brace7,11 19'-4"(5.89) Maximum vertical spacing between braces 30'-0"(9.14) Footnotes: 1. Applies to panels up to 25' (7.62 m) wide with a brace located at 0.2 times the panel width from each end. 2. These values can be applied to all concrete masonry units of 95 lb/ft3 (1522 kg/m3)density and greater and all solid concrete masonry. 3. PCL indicates portland cement/lime. MRC indicates mortar cement mortar. 4. MC indicates masonry cement mortar. 5. Assumes an unbonded condition between the wall and foundation such as at flashing - affects only unreinforced walls. 6. Exception: Walls 8' (2.44 m) tall and less above the ground do not need to be braced. 7. Assumes continuity of masonry other than at the base (i.e. no flashing other than at base). 8. Reinforced walls shall be considered unreinforced until grout is in place 12 hours. 9. Minimum reinforcement for 8" (203 mm) reinforced walls is No. 5 (No. 16M) vertical bars at 48" (1219 mm) on center and 40" (1016 mm) minimum lap splice for grout between 12 and 24 hours old or 30 inch (762 mm) splice length for grout 24 hours and over. 10. Minimum reinforcement for 12" (305 mm) reinforced walls is No. 5 (No. 16M) vertical bars at 72" (1829 mm) on center and 40" (1016 mm) minimum lap splice for grout between 12 and 24 hours old or 30 inch (762 mm) splice length for grout 24 hours and over. 11. For reinforced walls not requiring bracing, check adequacy of foundation to prevent overturning. 12. Cantilevered retaining walls must meet the bonded condition. 65

Wall height

6 in. (152 mm) 5 in. (127 mm) 5 in. (127 mm)

Wall See top connection detail

Vertical member

Wall plate typical each side at each brace height

16 in. x 16 in. x 1 2 in. (407 mm x 406 mm x 12.7 mm) plywood plate

16 in. (406 mm)

Brace height

1 2 max

4 in. x 4 in. x 16 ft (102 mm x 102 mm x 4.88 m) timber brace, No. 2 or better, any species

1

2 in. (12.7 mm) thick plywood plate typ. both sides-sandwich vertical member

Continuous 2 in. x 4 in. (51 mm x102 mm) bridging at midheight with (4) #8 screws, typ. at each timber space 2 in. x 4 in. (51 mm x 102 mm) vertical member typ.

(2) 3 8 in. (9.5 mm) diameter A307 through bolts, typ. 3

4 in. (19.0 mm) thick plywood gusset plate with (12) no. 8 screws each at vertical and timber brace member both sides

(1) 2 in. x 4 in. (51 mm x 102 mm) knee brace with (4) # 8 screws typ. at each brace end

Gusset plate-adjust geometry to accomate multiple braces-typ.

See footing anchor detail

Timber brace member

Vertical member

Footing plate

2 in. x 4 in. (51 mm x 102 mm) horizontal member typ.

Top Connection Detail

Concrete floor, augered anchor or concrete dead man of the following min. dimensions: Timber brace

3 ft (0.91 m) diameter x 3 ft 6 in. (1.07 m) deep for 32 ft (9.75 m) wall height 2 ft (0.61 m) diameter x 3 ft 6 in. (1.07 m) deep for 24 ft (7.32 m) wall height

3 in. (19.0 mm) thick plywood 4 gusset with (12) No. 8 wood screws each at vertical and timber brace member, typ. both sides

(2) 3 4 in. (19.0 mm) diameter wedge or epoxy set anchors spaced 6 in. (152 mm) apart minimum at standard embedment

1 ft 6 in. (0.46 m) diameter x 3 ft 6 in. (1.07 m) deep for 16 ft (4.88 m) wall height

Horizontal member 1

2 in. (127 mm) thick plywood plate-sandwich horizontal member

Note: This brace as detailed is adequate only for support heights of 14 ft 4 in. (4.37 m) or less. For greater support heights, the brace must be redesigned or a pipe or cable brace used.

Concrete footing per main drawing

Footing Anchor Detail Figure 2—Wood Brace Detail

the first working day. This leaves an extension of 8 in. (203 mm) above the top brace which is less than the 5'-4" (1.63 m) allowed (OK). The next level of masonry could be built to a height of 11'-4" + 12'-0" = 23'-4" (3.45 m + 3.66 m = 7.11 m). At the end of that working day, place the second brace at 24'0" - 5'-4" = 18'-8" (7.32 m - 1.63 m = 5.69 m). Check the vertical spacing between the braces: 18'-8" - 11'-4" = 7'-4" < 21'-4" (5.69 m - 3.45 m = 2.24 m < 6.50 m) (OK). Then after installing the brace, place the remaining final course for the total height of 24'-0" (7.32 m). Note: The bottom brace could be removed after the 12 or 24 hour curing period (depending on the splice length) as the reinforced wall section can span 21'-4" (6.50 m) vertically and the height of the top brace is only at 18'-8" (5.69 m).

WALLS SUBJECT TO BACKFILLING Unless concrete masonry basement walls are designed and built to resist lateral earth pressure as cantilever walls, they should not be backfilled until the first floor construction is in place and anchored to the wall or until the walls are adequately braced. Figure 3 illustrates one type of temporary lateral bracing being used in the construction of concrete masonry basement walls. Heavy equipment, such as bulldozers or cranes, should not be operated over the backfill during construction unless the basement walls are appropriately designed for the higher resulting loads. Ordinarily, earth pressures assumed in the design of 66

basement walls are selected on the assumption that the backfill material will be in a reasonably dry condition when placed. Since lateral earth pressures will increase as the moisture content of the earth is increased, basement walls should not be backfilled with saturated materials nor should backfill be placed when any appreciable amount of water is standing in the excavation. Similarly, water jetting or soaking should never be used to expedite consolidation of the backfill. Care should be taken to avoid subjecting the walls to impact loads, as would be imparted by earth sliding down a steep slope and hitting the wall. This could also damage waterproofing, dampproofing, or insulation applied to the walls. Also if needed, a unit can be left out at the bottom of a wall to prevent an unbalanced accumulation of water and replace before backfilling.

8f

Ensure waterproofing, drainage systems, and bracing are properly in place prior to backfilling

8f

.4 m t (2

.4 m t (2

)

)

2 x 10 plank 2 x 4 cleat 2 x 4 brace

2 x 4 struct brace Two 2 x 6 stakes driven into firm soil at least 12 in. (305 mm)

Figure 3—Typical Temporary Bracing for Concrete Masonry Basement Walls (ref. 2)

REFERENCES 1. Building Code Requirements for Masonry Structures, ACI 530-02/ASCE 5-02/TMS 402-02. Reported by the Masonry Standards Joint Committee, 2002. 2. NCMA Guide for Home Builders on Residential Concrete Masonry Walls, TR-134, National Concrete Masonry Association, 1994. 3. Standard Practice for Bracing Masonry Walls Under Construction, Council for Masonry Wall Bracing, July 2001.

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SURFACE BONDED CONCRETE MASONRY CONSTRUCTION Keywords: construction techniques, mortar, surface bonding

TEK 3-5A

Structural

(1998)

periods of 8 hours. Colored pigment can be incorporated into the surface bonding mortar to produce a finished surface without the need to paint. Surface bonded concrete masonry construction offers all of the benefits and advantages of conventional concrete masonry construction, such as: • fire safety • acoustic insulation • energy efficiency • lasting durability and beauty •

INTRODUCTION


SURFACE BONDED GROUNDED CONCRETE MASONRY

SURFACE BONDED UNGROUND CM UNITS

CONVENTIONAL CONCRETE MASONRY

SURFACE BONDED CONCRETE MASONRY






RELATIVE WALL STRENGTH, PERCENTAGE

Surface bonding is an economical construction technique which was first introduced in the late sixties by the U. S. Department of Agriculture for use in low cost housing. In surface bonded construction, concrete masonry units are laid dry and stacked, without mortar, to form walls. Walls are constructed with units that have been precision ground or honed to achieve a uniform bearing surface, or with shims placed periodically to maintain a level and plumb condition. Both sides of the wall are then coated with a thin layer of reinforced surface bondDESIGN STRENGTH ing mortar. The synthetic fibers which reinforce the surface bonding mortar impart a tensile strength of about 1500 psi Many structural and nonstructural tests have been per(10.3 MPa), producing a strong wall despite the relatively formed on surface bonded walls to establish design parameters thin thickness of material on each side. The surface coating for the system. on each side of the wall bonds the concrete masonry units The nonstructural properties, such as sound transmission together in a strong composite construction, and serves as a class, fire resistance period, and energy efficiency, of surface protective water resistant shield. bonded concrete masonry can be considered equivalent to a Surface bonded concrete masonry has a number of advanconventional mortared concrete masonry wall. tages: There are a few differences between the structural prop• Less time and skill are required for wall construction. erties of the two types of construction. These differences are In a 1972 study of mason productivity sponsored by the discussed in the following paragraphs, and are illustrated in U. S. Department of Housing NOTE: IN SOME COMPARISONS, THE STRENGTH OF SURFACE BONDED and Urban Development and WALLS IN VERTICAL SPAN HAS BEEN TWO TO THREE TIMES THAT OF other interested organizations, COMPANION WALLS OF CONVENTIONAL CONSTRUCTION. it was found that surface bonded 100 100 concrete masonry construction resulted in 70 percent greater productivity than that achievable with conventional construction. • The surface bonding mortar 50 50 provides excellent resistance to water penetration in addition to its function of holding the units together. Tests of surface bonded walls have repeatedly shown their resistance to wind driven SHEAR LOADS FLEXURAL LOADS COMPRESSIVE LOADS rain to be “excellent” even with VERTICAL HORIZONTAL SPANS SPANS wind velocities as great as 100 mph (161 km/h), and over test 68

Figure 1 for ungrouted, unreinforced walls. Although national building codes, such as the BOCA National Building Code and the Standard Building Code (refs. 1, 3) do not specifically address reinforced or grouted surface bonded walls, manufacturers of surface bonding mortars may have code-approved criteria for their products. Compressive Loads Resistance to vertical compressive loads depends primarily on the compressive strength of the concrete block used in the wall construction. Stronger units make stronger walls. With mortared construction, a rule of thumb is that the wall strength will generally be about seventy percent of the unit strength. In comparison, surface bonded walls built with unground concrete masonry units develop approximately thirty percent of the strength of the individual block. This reduced wall strength is depicted in Figure 1 for walls constructed with unground concrete masonry units. The lower value obtained with the unground units is due to a lack of solid bearing contact between units, due to the natural roughness of the concrete units. The mortar bed used in conventional construction compensates for this roughness and provides a uniform bearing between units. If the masonry unit bearing surfaces are ground flat and smooth before the wall is erected, results similar to those for a mortared wall can be expected. In Figure 1, note that surface bonded walls built with precision ground concrete masonry units are equally as strong in compression as the conventional construction. Flexural Resistance The flexural strength of a surface bonded wall is about the same as that of a conventional mortared wall, as shown in Figure 1. When walls are tested in the vertical span (i.e., a horizontal force, such as wind, is applied to a wall that is supported at the top and bottom) surfaced bonded walls and mortared walls have about the same average strength; failure occurs in the surface bonded coating due to tensile stress at or near one of the horizontal joints. With mortared construction, failure occurs at a horizontal joint with bond failure between the mortar and the masonry units. The data from numerous tests on surface bonded constructions led to an allowable stress of 18 psi (0.12 MPa) based on the gross area. When walls are laid in a running bond pattern, either with mortar joints or with surface bonding, and tested in the horizontal span, (i.e., a wall supported at each end is subjected to a horizontal wind force) the strength in bending depends primarily on the strength of the units. This is due to the interlocking of the masonry units laid when in a running bond configuration. In such tests in the horizontal span, the wall strength of the surface bonded wall is exactly the same as the conventional construction. In Table 1, an allowable flexural stress of 30 psi (0.21 MPa) is recommended for horizontal span when the units have been laid in running bond. Shear Strength The shear resistance of surface bonded construction is the same as that of conventional walls. With face shell mortar bedding, conventional concrete masonry walls averaged 42

Table 1—Allowable Stress, Gross Cross-Sectional Area, Dry-Stacked, Surface-Bonded Concrete Masonry Wallsa Compression:

45 psi (0.31 MPa)

Shear:

10 psi (0.07 MPa)

Flexural Tension:

Horizontal span: 30 psi (0.21 MPa) Vertical span: 18 psi (0.12 MPa)

a

References 1 & 3

psi (0.29 MPa) shear resistance, based on gross area. Nine surface bonded walls, 8 in. (203 mm) in thickness, had an average shear resistance of 39 psi (0.27 MPa), and three 6 in. (152 mm) thick surface bonded walls averaged 40 psi (0.28 MPa). These data are compared in Figure 1, and led to a recommended allowable shear stress of 10 psi (0.07 MPa) on the gross area (see Table 1). CONSTRUCTION The construction procedure for surface bonded walls is similar to that of conventional, except that mortar is not placed between the masonry units. Standard Practice for Construction of Dry-Stacked, Surface-Bonded Walls, ASTM C 946 (ref. 4), governs the construction methods. Care should be taken to ensure uncoated walls are adequately braced. Because the walls are constructed without mortar joints, surface bonded wall dimensions do not conform to the standard 4 in. (102 mm) design module. Wall and opening dimensions should be based on actual unit dimensions, which are typically 75/8 in. high by 155/8 in. long (194 by 397 mm). Materials Surface bonding mortar should comply with Standard Specification for Packaged, Dry, Combined Materials for Surface Bonding Mortar, ASTM C 887 (ref. 6), which governs flexural and compressive strength, sampling, and testing. ASTM C 946 requires Type I, moisture-controlled, concrete masonry units be used for surface bonded construction. Type I units must be in a dry condition when delivered to the job site. Walls laid using dry units will undergo less drying shrinkage after construction, hence minimizing cracks. Standard Specification for Loadbearing Concrete Masonry Units, ASTM C 90 (ref. 5) governs these requirements. As for mortared masonry construction, materials should be properly stored on site to prevent contamination by rain, ground water, mud, and other materials likely to cause staining or to have other deleterious effects. If the bearing surfaces of the concrete masonry units are unground, metal or plastic shims or mortar may occasionally be required between units to maintain the wall level and plumb. Shims must have a minimum compressive strength of 2000 psi (13.8 MPa) to ensure their long term durability after the wall is loaded. Metal shims, if used, should be corrosion resistant to reduce the possibility that they will corrode and bleed through the finished masonry at a later time. 69

Leveling Because the footing is not typically level enough to lay up the dry units without additional leveling, the first course of masonry units is laid in a mortar bed or set in the fresh footing concrete to obtain a level base for the remainder of the wall. Vertical head joints should not be mortared, even when the first course is mortar bedded, since mortar in the head joints will misalign the coursing along the wall length. When required, additional leveling courses are constructed in the wall. Leveling courses should be placed when: • the wall is out of level by more than 1/2 in. (13 mm) in 10 ft, • at each floor level, and • at a horizontal change in wall thickness (see Figure 2). After the first course of masonry units is laid level in a mortar bed, dry stacking proceeds with the remaining courses beginning with the corners, and followed by stacking, in running bond, between the corners. As they are dry stacked, the ends of the concrete masonry units should be butted together tightly. Small burrs should be removed prior to placement. After every fourth course, the wall should be checked for plumb and level. Crack Control Temperature and moisture movements have the potential to cause small vertical cracks in a masonry wall. These cracks are an aesthetic, rather than a structural, concern. In exposed concrete masonry, where shrinkage cracks may be objectionable, horizontal joint reinforcement, control joints, or bond beams are used to control cracking. The absence of a mortar bed joint in surface bonded walls means that there is no space in the wall for joint reinforcement, so control joints or bond beams are used for crack control. Control joints should be placed: 1. at wall openings and at changes in wall height and thickness 2. at wall intersections, at pilasters, chases, and recesses 3. in walls without openings, at intervals of 20 ft (6.1 m) when there are no bond beams in the construction, and at intervals of 60 ft (18.3 m) when bond beams are in-

Figure 2—Change in Wall Thickness

corporated every 4 ft (1.2 m) vertically. Control joints for surface bonded walls are similar to those for mortared concrete masonry. At the control joint location, the surface bonding mortar should be raked out and the joint caulked. Placing Accessories & Utilities The absence of a mortar bed joint in the construction also requires that the face shell and/or the cross web of the concrete masonry units be notched or depressed whenever wall ties or anchors must be embedded in the wall. A coarse rasp is typically used to make small notches, while deeper notches are cut with a masonry saw. Cores containing anchors or wall ties should be grouted, or other adequate anchorage should be provided. Electrical lines and plumbing are often located in the cores of concrete masonry units. These lines should be placed before the surface bonding mortar is applied, so that the masonry units are visible. Applying Surface Bonding Mortar Manufacturer’s recommendations should be followed for job site mixing of the premixed surface bonding mortar and application to the dry stacked concrete masonry wall. As with mortared masonry construction, clean water and mixing equipment should be used to prevent foreign materials from being introduced into the mortar. Batches should be mixed in full bag multiples only, to compensate for any segregation of materials within a bag. All materials should be mixed for 1 to 3 minutes, until the mixture is creamy, smooth, and easy to apply. Note that mixing time should be kept to a minimum, as overmixing can damage the reinforcing fibers. The stacked concrete masonry units should be clean and free of any foreign matter which would inhibit bonding of the plaster. Contrary to recommended practice with conventional mortared walls, the dry stacked concrete masonry units should be damp when the surface bonding plaster is applied to prevent water loss from the mortar due to suction of the units. Care should be taken to avoid saturating the units. It is very important that the surface bonding mortar be applied to both sides of the dry stacked wall since the wall strength and stability depend entirely on this coating. Premixed surface bonding mortars are smooth textured and easily applied by hand with a trowel. The workability is due to the short 1/2 in. (13 mm) glass fibers which reinforce the mixture. The mortar should be troweled on smoothly with a minimum thickness of 1/8 in. (3 mm). Surface bonding mortar can also be sprayed on. On large projects, use of a power sprayer greatly increases the coverage rate of the mortar and further reduces wall costs. As applied, the “sprayed-on” surface bonding mortar usually has a rougher surface texture than a troweled finish, and possesses slightly less tensile strength due to the lack of fiber orientation in the plane of the mortar coating. This can be overcome by troweling, hand or mechanical, following spray application of the mortar. Hand or mechanical troweling of the sprayed coating also assures that all gaps and crevices are filled. When a second coat of surface bonding mortar is ap70

plied, either by trowel or spray, it should be applied after the first coat is set, but before it is completely hardened or dried out. The second coat may be textured to achieve a variety of finishes. Joints in surface bonding mortar are weaker than a continuous mortar surface, and, for this reason, should not align with joints between masonry units. If application of the surface bonding mortar is discontinued for more than one hour, the first application should be stopped at least 11/4 in. (32 mm) from the horizontal edge of the concrete masonry unit. At the foundation, the surface bonding mortar should either form a cove between the wall and the footer or, for a slab on grade, should extend below the masonry onto the slab edge, as shown in Figure 3. These details help prevent water penetration at the wall/footer interface. Curing After surface bonding application, the wall must be properly cured by providing sufficient water for full hydration of the mortar, to ensure full strength development. The wall should be dampened with a water mist between 8 and 24 hours after surface bonding mortar application. In addition, the wall should be fog sprayed twice within the first 24 hours, although with pigmented mortar, this may be extended to 48 hours.

The recommendations above may need to be modified for either cold or hot weather conditions. For example, dry, warm, windy weather accelerates the water evaporation from the mortarrequiring more frequent fog spraying. At the end of the day, tops of walls should be covered to prevent moisture from entering the wall until the top is permanently protected. Typically, a tarp is placed over the wall, extending at least 2 ft (0.6 m) down both sides of the wall, and weighted down with lumber or masonry units. REFERENCES 1. BOCA National Building Code. Country Club Hills, IL: Building Officials and Code Administrators International, Inc. (BOCA), 1996. 2. Building Code Requirements for Masonry Structures, ACI 530-95/ASCE 5-95/TMS 402-95. Reported by the Masonry Standards Joint Committee, 1995. 3. Standard Building Code. Birmingham, AL: Southern Building Code Congress International, Inc. (SBCCI), 1997. 4. Standard Practice for Construction for Dry-Stacked, SurfaceBonded Walls, ASTM C 946-91 (1996)e1. American Society for Testing and Materials, 1996. 5. Standard Specification for Loadbearing Concrete Masonry Units, ASTM C 90-97. American Society for Testing and Materials, 1997.

wall-footing

wall-slab on grade Figure 3—Wall/Footing Interface

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Disclaimer: NCMA and the companies disseminating this technical information disclaim any and all responsibility and liability for the accuracy and the application of the information contained in this publication.




CONCRETE MASONRY VENEERS

TEK 3-6B Construction

(2005)

Keywords: anchors, cavity walls, joint reinforcement, multiwythe walls, veneer, wall ties INTRODUCTION In addition to its structural use as through-the-wall units, or as the exterior wythe of composite and noncomposite walls, concrete brick and architectural facing units are also used as veneer over various backing surfaces. The variety of surface textures, colors, and patterns available makes concrete masonry a versatile and popular exterior facing material. Architectural units such as split-face, scored, fluted, ground face, and slump are available in a variety of colors and sizes to complement virtually any architectural style.

1 in. (25 mm) weeps at 32 in. (813 mm) o.c., partially open head joints Flashing

VENEER—GENERAL Veneer is a nonstructural facing of brick, stone, concrete masonry or other masonry material securely attached to a wall or backing. Veneers provide the exterior wall finish and transfer out-of-plane loads directly to the backing, but they are not considered to add to the loadresisting capacity of the wall system. Backing material may be masonry, concrete, wood studs or steel studs. For the purposes of design, veneer is assumed to support no load other than its own weight. The backing must be designed to support the vertical and lateral loads imposed by the veneer in addition to the design loads on the wall since it is assumed the veneer does not add to the strength of the wall. Masonry veneers may be designed using engineered design methods to proportion the stiffness properties of the veneer and the backing to limit stresses in the veneer and achieve compatibility (ref. 4). As an alternative, prescriptive code requirements have been developed based on judgement and successful performance. The prescriptive requirements relate to size and spacing of anchors and methods of attachment, and are described in the following sections. In addition to structural requirements, differential movement between the veneer and its supports must be accommodated. Movement may be caused by tempera-

Concrete masonry backing

1 in. (25 mm) min. air space

Foundation

Anchored Veneer Concrete masonry backing Type S mortar Neat portland cement paste

Veneer unit with neat portland cement paste Type S mortar applied to veneer unit

3

to 1 1 2 in. (9.5 to 38 mm) 8

Adhered Veneer Figure 1—Types of Veneer Note: For clarity, not all construction elements are shown. See TEK 5-1B (ref. 3) for full construction details 72


ture changes, moisture-volume changes, or deflection. In concrete masonry, control joints and horizontal joint reinforcement effectively relieve stresses and accommodate small movements. Control joints should be placed in the veneer at the same locations as those in the backing, or as required to prevent excessive cracking. See Crack Control for Concrete Brick and Other Concrete Masonry Veneers (ref. 6) for further information. For exterior veneer, water penetration through the veneer is anticipated. Therefore, the backing system must be designed and detailed to resist water penetration and prevent water from entering the building. Flashing and weep holes in the veneer collect any water that penetrates the veneers and redirect it to the exterior. Partially open head joints are one preferred type of weep hole. They should be at least 1 in. (25 mm) high and spaced not more than 32 in. (813 mm) on center. If necessary, insects can be thwarted by inserting stainless steel wool into the opening or by using proprietary screens. For anchored veneer, open weep holes can also serve as vents, allowing air circulation in the cavity to speed the rate of drying. Additional vents may be installed at the tops of walls to further increase air circulation. More detailed information is contained in Concrete Masonry Veneer Details and Flashing Details for Concrete Masonry Walls (refs. 3, 5). Two types of veneer are discussed—anchored veneer and adhered veneer, as illustrated in Figure 1. They differ by the method used to attach the veneer to the backing. Unless otherwise noted, veneer requirements are those contained in Building Code Requirements for Masonry Structures (ref. 2).

The height and length of the veneered area is typically not limited by building code requirements. The exception is when anchored veneer is applied over frame construction. For wood stud backup, veneer height is limited to 30 ft (9.14 m) (height at plate) or 38 ft (11.58 m) (height at gable). Similarly, masonry veneer over steel stud backing must be supported by steel shelf angles or other noncombustible construction for each story above the first 30 ft (9.14 m) (height at plate) or 38 ft (11.58 m) (height at gable) (ref. 2). This support does not necessarily have to occur at the floor height, but instead can be provided at a window head or other convenient location. Where anchored veneers are not self-supporting, such as over openings, the veneer must be supported by noncombustible lintels or supports attached to noncombustible framing. Deflection of these horizontal supports is limited to 1/600 of the span or 0.3 in. (7.6 mm), whichever is smaller. Floors that support anchored veneers are subject to the same deflection limit. A 1 in. (25 mm) minimum air space must be maintained between the anchored veneer and backing to facilitate drainage. A 1 in. (25 mm) air space is considered appropriate if special precautions are taken to keep the air space clean (such as beveling the mortar bed away from the cavity). Otherwise, a 2 in. (51 mm) air space is preferred. As an alternative, proprietary insulating drainage products can be used. The maximum distance between the inside face of the veneer and the outside face of the backing is limited to 4 1/2 in. (114 mm), except for corrugated anchors used with wood

ANCHORED VENEER Anchored veneer is veneer which is supported laterally by the backing and supported vertically by the foundation or other structural elements. Anchors are used to secure the veneer and to transfer loads to the backing. Anchors and supports must be noncombustible and corrosion-resistant. In areas where the basic wind speed exceeds 110 mph (145 km/hr), the veneer must be designed using engineering philosophies, and the following prescriptive requirements may not be used. In areas where seismic activity is a factor, anchored veneer and its attachments must meet additional requirements to assure adequate performance in the event of an earthquake. Masonry units used for anchored veneer must be at least 2 5/8 in. (67 mm) thick.

Max. 1 1 4 in. (32 mm) Joint reinforcement as required Vertical Section W2.8 (MW 18) wire, minimum Max. clearance 16 in. (1.6 mm)

1

Pintle unit Plan View

Eye unit

Figure 2—Adjustable Anchors

W

g len av e

th

ude plit Am

Wid

th

Minimum width Minimum thickness Wavelength

= = =

Amplitude

=

Thickness

Minimum embedment, solid units = Minimum cover from exterior =

/ in. (22 mm) 0.03 in. (0.76 mm) 0.3 - 0.5 in. (7.6 - 13 mm) 0.06 - 0.10 in. (1.5 - 2.5 mm) 1 1/2 in. (38 mm) 5/8 in. (16 mm) 7 8

Figure 3—Corrugated Sheet Metal Anchor Requirements (ref. 2) 73

backing, where the maximum distance is 1 in. (25 mm). When anchored veneer is used as an interior finish supported on wood framing, the veneer weight is limited to 40 lb/ ft2 (195 kg/m2). Anchors Veneers may generally be anchored to the backing using corrugated sheet metal anchors, sheet metal anchors, wire anchors, joint reinforcement or adjustable anchors, although building codes may restrict the use of some anchors. Requirements for the most common anchor types are summarized in Figures 2 through 4. Attachment to Backing When masonry veneer is anchored to wood backing, each anchor is attached to the backing with a corrosion-resistant 8d

W 1.7, (MW 11) minimum

common nail, or a fastener with equivalent or greater pullout strength. For proper fastening of corrugated sheet metal anchors, the nail or fastener must be located within 1/2 in. (13 mm) of the 90° bend in the anchor. The exterior sheathing must be either water repellent with taped joints or be protected with a water repellent membrane, such as building paper ship lapped a minimum of 6 in. (152 mm) at seams, to protect the backing from any water which may penetrate the veneer. When masonry veneer is anchored to steel backing, adjustable anchors must be used to attach the veneer. Each anchor is attached with corrosion-resistant screws that have a minimum nominal shank diameter of 0.19 in. (4.8 mm). Coldformed steel framing must be corrosion resistant and should have a minimum base metal thickness of 0.043 in. (1.1 mm). Sheathing requirements are the same as those for wood stud backing. Masonry veneer anchored to masonry backing may be attached using wire anchors, adjustable anchors or joint reinforcement. Veneer anchored to a concrete backing must be attached with adjustable anchors. ADHERED VENEER

5

in. (16 mm) minumum 8

16 in. (406 mm) maximum

Figure 4—Requirements for Joint Reinforcement Used to Anchor Veneer (ref. 2)

Adhered veneer is veneer secured and supported through adhesion to a bonding material applied over the backing. Masonry units used in this application are limited to 25/8 in. (67 mm) thickness, 36 in. (914 mm) in any face dimension, 5 ft2 (0.46 m2) in total face area and 15 lb/ft2 (73 kg/m2) weight (ref. 2). In addition, the International Building Code (ref. 1) includes requirements for adhered masonry veneers used on interior walls. In this application, the code stipulates a maximum weight of 20 lb/ft2 (97 kg/m2). When the interior

Table 1—Anchor Spacing Requirements (ref. 2)

Maximum vertical spacing Maximum wall surface area per anchor

Anchor location Maximum horizontal spacing

Backing Masonry

Max. wall surface area, ft2 (m2)a

Type of anchor wire, adjustable, or joint reinforcement Concrete adjustable Wood stud adjustable two-piece, anchors of wire size W 1.7 (MW 11), or 22 gauge (0.8 mm) corrugated sheet metal all other anchors Steel stud adjustable

Anchor spacing Max. vertical Max. horizontal spacing, in. (mm) spacing, in. (mm)

2.67 (0.25) 2.67 (0.25)

18 (457) 18 (457)

32 (813) 32 (813)

2.67 (0.25) 3.5 (0.33) 2.67 (0.25)

18 (457) 18 (457) 18 (457)

32 (813) 32 (813) 32 (813)

Additional requirements: . When anchored veneer is laid in other than running bond, the veneer shall have joint reinforcement of at least one W1.7 (MW 11) wire, spaced at a maximum of 18 in. (457 mm) on center vertically to increase the flexural strength of the veneer in the horizontal span. . Around openings larger than 16 in. (406 mm) in either dimension, space anchors around perimeter of opening at a maximum of 3 ft (0.91 m) on center, and place anchors within 12 in. (305 mm) of opening. a

For Seismic Design Categories D, E and F, reduce maximum wall area supported by each anchor to 75% of values shown .

74

veneer is supported by wood construction, the wood backup must be designed for a maximum deflection of 1/600 of the span of the supporting wood member. Adhered veneer and its backing must also be designed to either have sufficient bond to withstand a shearing stress of 50 psi (345 kPa) based on the gross unit surface area after curing 28 days (refs. 1, 2), or be installed according to the following. A paste of neat portland cement is brushed on the backing and on the back of the veneer unit immediately prior to applying the mortar coat. This cement coating provides a good bonding surface for the mortar. Type S mortar is then applied to the backing and to each veneer unit in a layer slightly thicker than 3/8 in. (9.5 mm). Sufficient mortar should be used so that a slight excess is forced out the edges of the units. The units are then tapped into place to eliminate voids between the units and the backing which could reduce bond. The resulting thickness of mortar between the backing and veneer must be between 3/8 and 11/4 in. (9.5 and 32 mm). Mortar joints are tooled with a round jointer when the mortar is thumbprint hard. Backing materials for adhered veneer must be continuous and moisture-resistant (wood or steel frame backing with adhered veneer must be backed with a solid water repellent sheathing). Backing may be masonry, concrete, metal lath and portland cement plaster applied to masonry, concrete, steel framing or wood framing. Note that care must be taken when

adhered masonry veneer is used on steel frame or wood frame backing to limit deflection of the backing, which can cause veneer cracking or loss of adhesion. The surface of the backing material must be capable of securing and supporting the imposed loads of the veneer. Materials that may affect bond, such as dirt, grease, oil, or paint (except portland cement paint) should be cleaned off the backing surface prior to adhering the veneer. REFERENCES: 1. 2003 International Building Code. International Code Council, 2003. 2. Building Code Requirements for Masonry Structures, ACI 530-05/ASCE 5-05/TMS 402-05. Reported by the Masonry Standards Joint Committee, 2005. 3. Concrete Masonry Veneer Details, TEK 5-1B. National Concrete Masonry Association, 2003. 4. Structural Backup Systems for Masonry Veneer, TEK 16-3A. National Concrete Masonry Association, 1995. 5. Flashing Details for Concrete Masonry Walls, TEK 195A. National Concrete Masonry Association, 2004. 6. Crack Control for Concrete Brick and Other Concrete Masonry Veneers, TEK 10-4. National Concrete Masonry Association, 2001.

Provided by:




CONCRETE MASONRY FIREPLACES


filled with masonry. Immediately above the foundation walls, support for the combustion chamber and the hearth extension are necessary. The hearth extension may be supported by corbelling the masonry foundation wall, but is usually provided by a poured concrete slab that also supports the combustion chamber. Forming the concrete

Keywords: chimneys, combustion chamber, construction details, corbels, fireplaces, fire protection, footings INTRODUCTION The fireplace is an American tradition and remains today a central feature of the home. Concrete masonry, due to its inherent fire resistance and beauty, is a popular and versatile building material for constructing part or all of a fireplace. Noncombustible concrete masonry effectively isolates the fireplace fire from nearby combustible materials such as wood, plastic and insulation. In addition, because of concrete masonry's thermal mass, heat is stored in the concrete masonry itself. Thus, heat is not only radiated to the room from the fire, but also from the concrete masonry hours after the fire dies. Concrete masonry fireplaces are a safe and efficient source of auxiliary heat when properly designed and constructed. All fireplaces contain essentially the same elements: a base, combustion chamber, smoke chamber and chimney, as shown in Figure 1 for a single opening fireplace. Requirements herein are based on the 2003 International Residential Code (IRC) (ref. 1). BASE The fireplace base consists of the foundation and hearth extension support. The foundation consists of a concrete footing and concrete masonry foundation walls or a thickened slab for slab-on-grade construction (see Figure 1). Local building codes should be reviewed for design soil pressures for foundations. Void areas are often provided in the base to form an air passage for external combustion air, an ash pit or both. Nonessential void areas should be solidly

Air space not to exceed thickness of flue liner Flue

Chimney block or concrete brick

Chimney Fire clay flue liner

Mantle

Smoke dome

Parging

Throat damper Smoke shelf

Lintel angle 8 in. (203 mm), min. Lintel Fireplace opening height

4 in. (102 mm), min. Slope 30° from vertical, max. 20 in. (508 mm) min.

External air damper

Hearth extension

Ash drop

Air passageway

Double joists

Smoke chamber, height ≤ inside width of fireplace opening

Parging

4 in. (102 mm) concrete masonry

Combustion chamber

10 in. (254 mm) min. firebox thickness or 8 in. (203 mm) where fire brick lining is used External air supply register Non-combustible forming 8 in. (203 mm), min.

Reinforced concrete slab, 4 in. (102 mm) min. thickness Temporary forming

Flue liner support 8 in. (203 mm) min. smoke dome thickness if parged, 6 in. (152 mm) if firebrick

Base assembly Ash dump

Cleanout door

6 in. (152 mm), min. Concrete footing

12 in. (305 mm), min.

Figure 1—Single Opening Fireplace 76


(2003)

slab requires “block outs” for external combustion air dampers and ash drops if there are air passageways or ash pits incorporated into the base of the fireplace. If permanent forming is required at the top of the foundation walls, it must be a noncombustible material. Temporary wood forming is typically used to pour the hearth extension support. The forming should be placed so that the projected slab will meet a doubled wood floor joist, and be such that it can be easily removed. The concrete slab must be at least 4 in. (102 mm) thick, reinforced and capable of resisting thermal stresses resulting from high temperatures. The hearth extension must extend at least 16 in. (406 mm) in front of the fireplace face and at least 8 in. (203 mm) beyond each side of the fireplace opening for fireplaces with openings that are less than 6 ft2 (0.56 m2). If the area of the fireplace opening is 6 ft2 (0.56 m2) or larger, the hearth extension must be 20 in. (508 mm) in front of the fireplace face and at least 12 in. (305 mm) beyond each side of the opening. Because the hearth extension must be constructed of noncombustible materials, concrete brick or decorative concrete masonry units are often used to construct the hearth extension. COMBUSTION CHAMBER

The fireplace opening should be based on the room size for aesthetics and to prevent overheating the room. Suggested fireplace opening widths are provided in Table 1. Once the opening width is selected, the dimensions of the masonry combustion chamber may be determined using Table 2. The steel angle lintel used above the fireplace opening should not be solidly embedded in mortar. With the ends free to move, lintel expansion due to high temperatures will not crack the masonry. The use of noncombustible fibrous insulation at the ends of the lintel angle will usually compensate for this expansion and eliminate cracking problems. The size and position of the throat is critical for proper burning and draft. The fireplace throat should be as wide as the firebox and should be not less than 8 in. (203 mm) above the fireplace opening. SMOKE CHAMBER The smoke chamber consists of the damper, smoke shelf, smoke dome and surrounding concrete masonry. The damper, which is critical for proper performance, is placed directly over the throat. The metal damper, like the lintel over the fireplace opening, should not be solidly embedded in mortar. When the fireplace is not in use, the damper should be closed to prevent heat loss. When a fire is started, the damper should be wide open. Once the

The combustion chamber consists of the hearth extension, the firebox and surrounding masonry and the throat. Fire brick, if used, must conform to Standard Classification of Table 1—Suggested Width of Fireplace Openings Appropriate Fireclay and High-Alumina Refractory Brick, ASTM to Size of Room (ref. 5) C 27 or Standard Specification for Firebox Brick for Residential Fireplaces, C 1261 (refs. 2, 3), laid to form Size of room, Width of fireplace opening, in. (mm) a firebox wall thickness of at least 2 in. (51 mm). Fire brick ft x ft (m x m) in short wall in long wall is laid using medium-duty refractory mortar conform10 x 14 (3.05 x 4.27) 24 (610) 24 to 32 (610-813) ing to Standard Test Method for Pier Test for Refrac12 x 16 (3.66 x 4.88) 28 to 36 (711-914) 32 to 36 (813-914) 1 tory Mortars, ASTM C 199 (ref. 4), with /4 in. (6.35 mm) 12 x 20 (3.66 x 6.10) 32 to 36 (813-914) 36 to 40 (914-1,016) mortar joints maximum. The total minimum thickness of 12 x 24 (3.66 x 7.32) 32 to 36 (813-914) 36 to 48 (914-1,219) the back and side walls must be 8 in. (203 mm) of solid 14 x 28 (4.27 x 8.53) 32 to 40 (813-1,016) 40 to 48 (1,016-1,219) masonry including the lining. When no lining is used, 16 x 30 (4.88 x 9.14) 36 to 40 (914-1,016) 48 to 60 (1,219-1,524) this minimum thickness is 10 in. (254 mm). 20 x 36 (6.10 x 10.97) 40 to 48 (1,016-1,219) 48 to 72 (1,219-1,829) Table 2—Single-Opening Fireplace Dimensions, Inches (ref. 5)a Opening Width Height 24 26 28 30 32 36 40 42 48 54 60 60 72 a

24 24 24 29 29 29 29 32 32 37 37 40 40

Firebox Throat Rear wall depth Depth Width Vertical Splayed height height 16 11 14 18 83 / 4 16 13 14 18 83 / 4 16 15 14 18 83 / 4 16 17 14 23 83 / 4 16 19 14 23 83 / 4 16 23 14 23 83 / 4 16 27 14 23 83 / 4 16 29 16 24 83 / 4 18 33 16 24 83 / 4 20 37 16 29 13 22 42 16 29 13 22 42 18 30 13 22 54 18 30 13

Smoke chamber

Steel angles

Width Height Shelf Length depth 32 19 12 36 34 21 12 36 36 21 12 36 38 24 12 42 40 24 12 42 44 27 12 48 48 29 12 48 50 32 12 54 56 37 14 60 68 45 12 66 72 45 14 72 72 45 14 72 84 56 14 84

Size 3 x 3 x 1/4 3 x 3 x 1/4 3 x 3 x 1/4 3 x 3 x 1/4 3 x 3 x 1/4 3 x 3 x 1/4 3 x 3 x 1/4 31/2 x 3 x 1/4 31/2 x 3 x 1/4 31/2 x 3 x 1/4 31/2 x 3 x 1/4 31/2 x 3 x 1/4 5 x 31/2 x 5/16

For millimeters, multiply inches by 25.4. 77

fire is burning readily, the damper should be adjusted to produce more efficient combustion. Keeping the damper wide open reduces the fireplace efficiency. For convenience and safety, a rotary controlled damper that is adjusted with a control on the face of the fireplace is preferred, since adjusting a poker controlled damper usually requires reaching into the firebox. The masonry above the damper should be supported on a second lintel angle (if required) and not on the damper. This lintel must be allowed to expand independently and thus should not be solidly embedded in the masonry. Immediately behind the damper is the smoke shelf, which checks down drafts. Any down drafts strike the smoke shelf and are diverted upward by the damper assembly. The smoke shelf may be curved to assist in checking down drafts, but flat smoke shelves perform adequately. The smoke dome should be constructed so that the side walls and front wall taper inward to form the chimney support. The walls of the smoke dome should be solid masonry or hollow unit masonry grouted solid and should provide a minimum of 8 in. (203 mm) of solid masonry between the smoke dome and exterior surfaces when no lining is used. When the smoke dome is lined using fire brick at least 2 in. (51 mm) thick or vitrified clay at least 5 /8 in. (16 mm) thick, this minimum thickness is reduced to 6 in. (152 mm). The inside of the smoke dome should be parged to reduce friction and help prevent gas and smoke leakage (when the inside is formed by corbelling the masonry, this parging is required). For ease of construction, a high form damper may be used. High form dampers are constructed such that the damper, smoke shelf and smoke dome are contained in one metal unit. Additionally, fireplace inserts may be used. Inserts include the elements of the high form damper as well as the firebox. The inserts are placed directly on the firebrick hearth. FLUE AND CHIMNEY The chimney should be positioned so that it is centered on the width of the fireplace and the back of the flue liner aligns with the vertical rear surface of the smoke dome. This configuration funnels the smoke and gases from the fire into the chimney. The chimney is constructed directly over the smoke shelf and consists of a flue liner and a chimney wall. For residential fireplaces, theflueliningmaybeaclayflueliningcomplyingwithStandard Specification for Clay Flue Linings, ASTM C 315 (ref. 6), a listed chimney lining system complying with Standard for Safety for Chimney Liners, UL 1777 (ref. 7) or other approved system or material. Fireclay flue liners are laid in medium-duty refractory mortar conforming to Standard Test Method for Pier Test for Refractory Mortars, ASTM C 199 (ref. 4), with flush mortar joints on the inside. Care should be taken to use only enough mortar to make the joint. Flue lining installation should conform to Standard Practice for Installing Clay Flue Lining, ASTM C 1283 (ref. 8). The chimney wall must be constructed of solid masonry units or hollow units grouted solid, and be at least 4 in. (102 mm) in nominal thickness. The chimney wall should be separated from the flue lining by an airspace or insulation not thicker than the thickness of the flue lining to permit the flue lining, when hot, to expand freely without cracking the chimney wall. Note that in Seismic Design Categories D and E, additional reinforcement and anchorage requirements apply to masonry chimneys in accor-

dance with applicable building codes. To ensure the fireplace draws adequately, flue size is determined by the shape of the flue and the size of the fireplace opening (see Table 3). The International Residential Code ( ref. 1) has an Option 2 where the flue size is based on chimney height as well as the fireplace opening area. The chimney must extend at least 3 ft (914 mm) above the point where the chimney passes through the roof and at least 2 ft (610 mm) above any part of the building within 10 ft (3,048 mm) of the chimney (see Figure 2). Higher chimneys may be required for adequate draft. Good draft is normally achieved with 15 ft (4,572 mm) high chimneys (measured from the top of the fireplace opening to the top of the chimney). The chimney must be capped to resist water penetration. A mortar wash that is feathered to the edge of the chimney wall is not an adequate cap. The cap should be either cast-in-place or precast concrete, as shown in Figure 2. Metal pan flashing over the top of the chimney will also perform adequately. CLEARANCES AND FIREBLOCKING A minimum 2 in. (51 mm) airspace must be maintained between combustible framing and masonry fireplaces, or 4 in. (102 mm) from the back face, and any combustibles, excluding trim and the edges of sheathing materials. The IRC (ref. 1) contains minimum clearances between masonry fireplaces or chimneys and exposed combustible trim and the edges of sheathing materials such as wood siding, flooring and drywall as well as mantles. These air spaces should be firestopped using noncombustible materials as precribed by the building code. A 2 in. (51 mm) clearance is required around the perimeter of the chimney wall. This clear space should be firestopped in the same manner as described for fireplaces. If the entire perimeter of the chimney wall is outside the building, including soffits or cornices, the clearance between the chimney wall and combustibles may be reduced to 1 in. (25 mm). ENERGY EFFICIENCY Proper fireplace design and operation helps maximize the efficiency. Maintaining efficient fuel consumption by properly adjusting the damper is critical. There are several other ways to significantly improve the performance of the concrete masonry fireplace. For example, positioning the fireplace on interior rather than exterior walls reduces heat loss when the fireplace is not in operation, and increases the amount of usable radiant heat from the concrete masonry. Fireplace efficiency can also be improved by introducing external air into the firebox for draft and combustion (not within Table 3—Minimum Flue Net Cross-Sectional Area for Masonry Fireplaces Flue shape

Net cross-sectional area of flue, fraction of fireplace opening size 1 /12 1 /10

Round Square Rectangular: aspect ratio < 2 to 1 aspect ratio > 2 to 1

1

/10 /8

1

78

the garage or basement. An external combustion air system requires a damper in the firebox, adequate ducting or air passageways and a grill or louver at the exterior opening. The external air damper should permit the control of both the direction and volume of the airflow for temperature control. The damper should be capable of directing air flow towards the back of the firebox so that when down drafts or negative pressures occur, hot ashes or embers are not forced into the room.

Cast-in-Place Cap: Concrete cap 4 in. (102 mm) thick, min.

Precast Cap:

Noncombustible resilient sealant

Temporary forming

10 ft (3,048 mm) 4 in. (102 mm) max. Precast cap

1

2 in. (13 mm) min. galvanized hardware cloth reinforcement

24 in. (610 mm) min.

2 in. (51 mm) min. typ.

36 in. (914 mm) min.

REFERENCES 1. 2003 International Residential Code. International Code Council, 2003. 2. Standard Classification of Fireclay and HighAlumina Refractory Brick, ASTM C 27-98. ASTM International, 1998. 3. Standard Specification for Firebox Brick for Residential Fireplaces, ASTM C 1261-98. ASTM International, 1998. 4. Standard Test Method for Pier Test for Refractory Mortars, ASTM C 199-84 (2000). ASTM International, 2000. 5. Book of Successful Fireplaces, How to Build, Decorate and Use Them, 20th Edition, by R. J. and M.J. Lytle, Structures Publishing Company, Farmington, Michigan, 1977. 6. Standard Specification for Clay Flue Linings, ASTM C 315-02. ASTM International, 2002. 7. Standard for Safety for Chimney Liners, UL 1777. Underwriters Laboratory, 1996. 8. Standard Practice for Installing Clay Flue Lining, ASTM C 1283-02. ASTM International, 2002.

Counter flashing

Roof rafter

2 in. (51 mm) clearance to framing, min.

Base flashing (fire stop) Fire clay flue liner Air space not to exceed thickness of flue liner Concrete brick or block 4 in. (102 mm) min. 1

2 in. (13 mm) non-combustible wall board (fire stop)

Ceiling joist

Figure 2—Chimney Roof Penetration

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NCMA TEK

Provided by: BetcoSupreme National Concrete Masonry Association


CONCRETE MASONRY CONSTRUCTION

TEK 3-8A

Construction

(2001)

INTRODUCTION Concrete masonry is a popular building material because of its strength, durability, economy, and its resistance to fire, noise, and insects. To function as designed however, concrete masonry buildings must be constructed properly. This TEK provides a brief overview of the variety of materials and construction methods currently applicable to concrete masonry. In addition, a typical construction sequence is described in detail.

a unit. Grout is used to fill masonry cores or wall cavities to improve the structural performance and/or fire resistance of masonry. Grout is most commonly used in reinforced construction, to structurally bond the steel reinforcing bars to the masonry, allowing the two elements to act as one unit in resisting loads. Reinforcement incorporated into concrete masonry structures increases strength and ductility, providing increased resistance to applied loads and, in the case of horizontal reinforcement, to shrinkage cracking. Specifications governing material requirements are listed in Table 1.

MATERIALS

CONSTRUCTION METHODS

Keywords: ASTM specifications, bond patterns, cleaning, construction techniques, construction tolerances, grout,

The constituent masonry materials: concrete block, morMortared Construction tar, grout, and steel, each contribute to the performance of a Most concrete masonry construction is mortared construcmasonry structure. Concrete masonry units provide strength, tion, i.e., units are bonded together with mortar. Varying the durability, fire resistance, energy efficiency, and sound attenubond or joint pattern of a concrete masonry wall can create a ation to a wall system. In addition, concrete masonry units are wide variety of interesting and attractive appearances. In admanufactured in a wide variety of sizes, shapes, colors, and architectural finishes to achieve any number of appearances and functions. The Concrete Masonry Shapes and Sizes Manual (ref. 4) illustrates a broad sampling of available units. While mortar constitutes approximately 7% of a typical masonry wall area, its influence on the performance of a wall is significant. Mortar bonds the individual masonry units together, allowing them to act as a composite structural assembly. In addition, mortar seals joints against moisture and air leakage and bonds to joint reinforcement, anchors, and ties to help enPlacement of Concrete Masonry Units sure all elements perform as TEK 3-8A © 2001 National Concrete Masonry Association (replaces TEK 3-8)

80

Table 1—Masonry Material Specifications Units Loadbearing Concrete Masonry Units, ASTM C 90 Concrete Building Brick, ASTM C 55 Calcium Silicate Face Brick (Sand-Lime Brick), ASTM C 73 Nonloadbearing Concrete Masonry Units, ASTM C 129 Prefaced Concrete and Calcium Silicate Masonry Units, ASTM C 744 Mortar Mortar for Unit Masonry, ASTM C 270 Grout Grout for Masonry, ASTM C 476 Reinforcement Axle-Steel Deformed and Plain Bars for Concrete Reinforcement, ASTM A 617 Deformed and Plain Billet-Steel Bars for Concrete Reinforcement, ASTM A 615 Epoxy-Coated Reinforcing Steel Bars, ASTM A 775 Low-Alloy Steel Deformed Bars for Concrete Reinforcement, ASTM A 706 Rail-Steel Deformed and Plain Bars for Concrete Reinforcement, ASTM A 616 Zinc-Coated (Galvanized) Steel Bars for Concrete Reinforcement, ASTM A 767 Masonry Joint Reinforcement, ASTM A 951 Ties & Anchors dition, the strength of the masonry can be influenced by the bond pattern. The most traditional bond pattern for concrete masonry is running bond, where vertical head joints are offset by half the unit length. Excluding running bond construction, the most popular bond pattern with concrete masonry units is stack bond. Although stack bond typically refers to masonry constructed so that the head joints are vertically aligned, it is defined as masonry laid such that the head joints in successive courses are horizontally offset less than one quarter the unit length (ref. 2). Concrete Masonry Bond Patterns (ref. 3) shows a variety of bond patterns and describes their characteristics. Dry-Stacked Construction The alternative to mortared construction is dry-stacked (also called surface bonded) construction, where units are placed without any mortar, then both surfaces of the wall are coated with surface bonding material. Shims or ground units are used to maintain elevations. This construction method results in faster construction, and is less dependent on the skill of the laborer than mortared construction. In addition, the surface bonding coating provides excellent rain penetration resistance. Surface Bonded Concrete Masonry Construction (ref. 9) con-

tains further information on this method of construction. CONSTRUCTION SEQUENCE Mixing Mortar To achieve consistent mortar from batch to batch, the same quantities of materials should be added to the mixer, and they should be added in the same order. Mortar mixing times, placement methods, and tooling must also be consistent to achieve uniform mortar for the entire job. In concrete masonry construction, site-mixing of mortar should ideally be performed in a mechanical mixer to ensure proper uniformity throughout the batch. Mortar materials should be placed in the mixer in a similar manner from batch to batch to maintain consistent mortar properties. Typically, about half the mixing water is added first into a mixer. Approximately half the sand is then added, followed by any lime. The cement and the remainder of the sand are then added. As the mortar is mixed and begins to stiffen, the rest of the water is added. Specification for Masonry Structures (ref. 7) requires that these materials be mixed for 3 to 5 minutes. If the mortar is not mixed long enough, the mortar mixture may not attain the uniformity necessary for the desired performance. A longer mixing time can increase workability, water retention, and board life. The mortar should stick to the trowel when it is picked up, and slide off the trowel easily as it is spread. Mortar should also hold enough water so that the mortar on the board will not lose workability too quickly, and to allow the mason to spread mortar bed joints ahead of the masonry construction. The mortar must also be stiff enough to initially support the weight of the concrete masonry units. To help keep mortar moist, the mortarboard should be moistened when a fresh batch is loaded. When mortar on the board does start to dry out due to evaporation, it should be retempered. To retemper, the mortar is mixed with a small amount of additional water to improve the workability. After a significant amount of the cement has hydrated, retempering will no longer be effective. For this reason, mortar can be retempered for only 11/2 to 21/2 hours after initial mixing, depending on the site conditions. For example, dry, hot, and windy conditions will shorten the board life, and damp, cool, calm conditions will increase the board life of the mortar. Mortar should be discarded if it shows signs of hardening or if 21/2 hours have passed since the original mixing. Placing Mortar Head and bed joints are typically 3/8 in. (10 mm) thick, except at foundations. Mortar should extend fully across bedding surfaces of hollow units for the thickness of the face shell, so that joints will be completely filled. Solid units are required to be fully bedded in mortar. Although it is important to provide sufficient mortar to properly bed concrete masonry units, excessive mortar should not extend into drainage cavities or into cores to be grouted. For grouted masonry, mortar protrusions extending more than 1 /2 in. (13 mm) into cells or cavities to be grouted should be removed (ref. 7). 81

The Importance of Laying to the Line Experienced masons state that they can lay about five times as many masonry units when working to a mason line than when using just their straightedge. The mason line gives the mason a guide to lay the block straight, plumb, at the right height, and level. The line is attached so that it gives a guide in aligning the top of the course. If a long course is to be laid, a trig may be placed at one or more points along the line to keep the line from sagging. Before work begins, the mason should check to see that the line is level, tight, and will not pull out. Each mason working to the same line needs to be careful not to lay a unit so it touches the line. This will throw the line off slightly and cause the rest of the course to be laid out of alignment. The line should be checked from time to time to be certain it has remained in position. PLACING UNITS The Foundation Before building the block wall, the foundation must be level, and clean so that mortar will properly adhere. It must also be reasonably level. The foundation should be free of ice, dirt, oil, mud, and other substances that would reduce bond. Laying Out the Wall Taking measurements from the foundation or floor plan and transferring those measurements to the foundation, footing, or floor slab is the first step in laying out the wall. Once two points of a measurement are established, corner to corner, a chalk line is marked on the surface of the foundation to establish the line to which the face of the block will be laid. Since a chalk line can be washed away by rain, a grease crayon, line paint, nail or screwdriver can mark the surface for key points along the chalk line, and a chalk line re-snapped along these key points. After the entire surface is marked for locations of walls, openings, and control joints, a final check of all measurements should be made. The Dry Run—Stringing Out The First Course Starting with the corners, the mason lays the first course without any mortar so a visual check can be made between the dimensions on the floor or foundation plan and how the first course actually fits the plan. During this dry layout, concrete blocks will be strung along the entire width and length of the foundation, floor slab, and even across openings. This will show the mason how bond will be maintained above the opening. It is helpful to have 3/8 in. (10 mm) wide pieces of wood to place between block as they are laid dry, to simulate the mortar joints. At this dry run the mason can check how the block will space for openings which are above the first course—windows, etc., by taking away block from the first course and checking the spacing for the block at the higher level. These checks will show whether or not units will need to be cut. Window and door openings should be double checked with the window shop drawings prior to construction. When this is done, the mason marks the exact location

and angle of the corners. It is essential that the corner be built as shown on the foundation or floor plan, to maintain modular dimensions. Laying the Corner Units Building the corners is the most precise job facing the mason as corners will guide the construction of the rest of the wall. A corner pole can make this job easier. A corner pole is any type of post which can be braced into a true vertical position and which will hold a taut mason’s line without bending. Corner poles for concrete block walls should be marked every 4 or 8 in. (102 to 203 mm), depending on the course height, and the marks on both poles must be aligned such that the mason’s line is level between them. Once the corner poles are properly aligned, the first course of masonry is laid in mortar. Typically, a mortar joint between 1 /4 and 3/4 in. (6.4 to 19 mm) is needed to make up for irregularities of the footing surface. The initial bed joint should be a full bed joint on the foundation, footing, or slab. In some areas, it is common practice to wet set the initial course of masonry directly in the still damp concrete foundation. Where reinforcing bars are projecting from the foundation footing or slab, the first course is not laid in a full mortar bed. In this case, the mason leaves a space around the reinforcing bars so that the block will be seated in mortar but the mortar will not cover the area adjacent to the dowels. This permits the grout to bond directly to the foundation in these locations. After spreading the mortar on the marked foundation, the first block of the corner is carefully positioned. It is essential that this first course be plumb and level. Once the corner block is in place, the lead blocks are set—three or four blocks leading out from each side of the corner. The head joints are buttered in advance and each block is lightly shoved against the block in place. This shove will help make a tighter fit of the head joint, but should not be so strong as to move the block already in place. Care should be taken to spread mortar for the full height of the head joint so voids and gaps do not occur. If the mason is not working with a corner pole, the first course leads are checked for level, plumb, and alignment with a level. Corners and leads are usually built to scaffold height, with each course being stepped back one half block from the course below. The second course will be laid in either a full mortar bed or with face shell bedding, as specified. Laying the Wall Each course between the corners can now be laid easily by stretching a line between. It should be noted that a block has thicker webs and face shells on top than it has on the bottom. The thicker part of the webs should be laid facing up. This provides a hand hold for the mason and more surface area for mortar to be spread. The first course of block is thereafter laid from corner to corner, allowing for openings, with a closure block to complete the course. It is important that the mortar for the closure block be spread so all edges of the opening between blocks and all edges of the closure block are buttered 82

before the closure block is carefully set in place. Also, the location of the closure block should be varied from course to course so as not to build a weak spot into the wall. The units are leveled and plumbed while the mortar is still soft and pliable, to prevent a loss of mortar bond if the units need to be adjusted. As each block is put in place, the mortar which is squeezed out should be cut off with the edge of the trowel and care should be taken that the mortar doesn’t fall off the trowel onto the wall or smear the block as it is being taken off. Should some mortar get on the wall, it is best to let it dry before taking it off. All squeezed out mortar which is cut from the mortar joints can either be thrown back onto the mortar board or used to butter the head joints of block in place. Mortar which has fallen onto the ground or scaffold should never be reused. At this point, the mason should: • Use a straightedge to assure the wall is level, plumb and aligned. • Be sure all mortar joints are cut flush with the wall, awaiting tooling, if necessary. • Check the bond pattern to ensure it is correct and that the spacing of the head joints is right. For running bond, this is done by placing the straightedge diagonally across the wall. If the spacing of head joints is correct, all the edges of the block will be touched by the straightedge. • Check to see that there are no pinholes or gaps in the mortar joints. If there are, and if the mortar has not yet taken its first set, these mortar joint defects should be repaired with fresh mortar. If the mortar has set, the only way they can be repaired is to dig out the mortar joint where it needs repairing, and tuckpoint fresh mortar in its place. Tooling Joints When the mortar is thumbprint hard, the head joints are tooled, then the horizontal joints are finished with a sled runner and any burrs which develop are flicked off with the blade of the trowel. When finishing joints, it is important to press firmly, without digging into the joints. This compresses the surface of the joint, increasing water resistance, and also promotes bond between the mortar and the block. Unless otherwise required, joints should be tooled with a rounded jointer, producing a concave joint. Once the joints are tooled, the wall is ready for cleaning. Cleanup Masonry surfaces should be cleaned of imperfections that may detract from the final appearance of the masonry structure including stains, efflorescence, mortar droppings, grout droppings, and general debris. Cleaning is most effective when performed during the wall construction. Procedures such as skillfully cutting off excess mortar and brushing the wall clean before scaffolding is raised, help reduce the amount of cleaning required. When mortar does fall on the block surface, it can often be removed more effectively by letting it dry and then knocking it off the surface. If there is some staining on the face of the

block, it can be rubbed off with a piece of broken block, or brushed off with a stiff brush. Masons will sometimes purposefully not spend extra time to keep the surface of the masonry clean during construction because more aggressive cleaning methods may have been specified once the wall is completed. This is often the case for grouted masonry construction where grout smears can be common and overall cleaning may be necessary. The method of cleaning should be chosen carefully as aggressive cleaning methods may alter the appearance of the masonry. The method of cleaning can be tested on the sample panel or in an inconspicuous location to verify that it is acceptable. Specification for Masonry Structures (ref. 7) states that all uncompleted masonry work should be covered at the top for protection from the weather. DIMENSIONAL TOLERANCES While maintaining tight construction tolerances is desirable to the appearance, and potentially to the structural integrity of a building, it must be recognized that factors such as the condition of previous construction and non-modularity of the project may require the mason to vary the masonry construction slightly from the intended plans or specifications. An example of this is when a mason must vary head or bed joint thicknesses to fit within a frame or other preexisting construction. The ease and flexibility with which masonry construction accommodates such change is one advantage to using masonry. However, masonry should still be constructed within certain tolerances to ensure the strength and appearance of the masonry is not compromised. Specification for Masonry Structures (ref. 7) contains site tolerances for masonry construction which allow for deviations in the construction that do not significantly alter the structural integrity of the structure. Tighter tolerances may be required by the project documents to ensure the final overall appearance of the masonry is acceptable. If site tolerances are not being met or cannot be met due to previous construction, the Architect/Engineer should be notified. Mortar Joint Tolerances Mortar joint tolerances are illustrated in Figure 1. Although bed joints should be constructed level, they are permitted to vary by ± 1/2 in. (13 mm) maximum from level provided the joint does not slope more than ± 1/4 in. (6.4 mm) in 10 ft (3.1 m). Collar joints, grout spaces, and cavity widths are permitted to vary by -1/4 in. to + 3/8 in. (6.4 to 9.5 mm). Provisions for cavity width are for the space between wythes of non-composite masonry. The provisions do not apply to situations where the masonry extends past floor slabs or spandrel beams. Dimensions of Masonry Elements Figure 2 shows tolerances that apply to walls, columns, and other masonry building elements. It is important to note that the specified dimensions of concrete masonry units are 83

/8 in. (9.5 mm) less than the nominal dimensions. Thus a wall specified to be constructed of 8 in. (203 mm) concrete masonry units should not be rejected because it is 7 5/8 in. (194 mm) thick, less than the apparent minimum of 7 3/4 in. (197 mm) (8 in. (203 mm) minus the 1/4 in. (6.4 mm) tolerance). Instead the tolerance should be applied to the 7 5/8 in. (194 mm) specified dimension. 3

Location of Elements Requirements for location of elements are shown in Figures 4 and 5.

Plumb, Alignment, and Levelness of Masonry Elements Tolerances for plumbness of masonry walls, columns, and other building elements are shown in Figure 3. Masonry building elements should also maintain true to a line within the same tolerances as variations from plumb. Columns and walls continuing from one story to another may vary in alignment by ± 3/4 in. (19 mm) for nonloadbearing walls or columns and by ± 1/2 in. (13 mm) for bearing walls or columns. The top surface of bearing walls should remain level within a slope of ± 1/4 in. (6.4 mm) in 10 ft (3.1 m), but no more than ± 1/2 in. (13 mm).

HEAD JOINT THICKNESS - 1/4 IN., + 3/8 IN. = 3/8 IN.

Figure 3—Permissible Variations From Plumb BED JOINT THICKNESS= 3/8 IN. +_ 1/8 IN.

FOOTING

INITIAL BED JOINT THICKNESS= 1/ IN. MIN. 4 3/4 IN. MAX.

Figure 1—Mortar Joint Tolerances

Figure 4—Location Tolerances in Plan

Figure 2—Element Cross Section and Elevation Tolerances

Figure 5—Location Tolerances in Story Height 84

REFERENCES 1. Building Block Walls, VO 6. National Concrete Masonry Association, 1988. 2. Building Code Requirements for Masonry Structures, ACI 530-99/ASCE 5-99/TMS 402-99. Reported by the Masonry Standards Joint Committee, 1999. 3. Concrete Masonry Bond Patterns, TEK 14-6. National Concrete Masonry Association, 1999. 4. Concrete Masonry Shapes and Sizes Manual, CM 260A. National Concrete Masonry Association, 1997. 5. Inspection of Concrete Masonry Construction, TR 156. National Concrete Masonry Association, 1996. 6. Nolan, K. J. Masonry & Concrete Construction. Craftsman Book Company, 1982. 7. Specification for Masonry Structures, ACI 530.1-99/ASCE 6-99/TMS 602-99. Reported by the Masonry Standards Joint Committee, 1999. 8. Standard Specification for Loadbearing Concrete Masonry Units, ASTM C 90-00. American Society for Testing and Materials, 2000. 9. Surface Bonded Concrete Masonry Construction, TEK 3-5A. National Concrete Masonry Association, 1998.

Provided by: BetcoSupreme Disclaimer: NCMA and the companies disseminating this technical information disclaim any and all responsibility and liability for the accuracy and the application of the information contained in this publication.





STRATEGIES FOR TERMITE RESISTANCE

TEK 3-9A

Construction

(2000)

Keywords: bond beams, capping concrete masonry walls,

crack control, Formosan termite, grouting procedures, termites, termite entry, termite resistance INTRODUCTION

very versatile with an almost endless array of architectural Termites are distributed widely throughout the United shapes, sizes textures and colors available. When wood is States, causing substantial damage to unprotected wood buildused as a construction material, the further the food source is ings. Although there are over forty species of termites in the from the soil, the lower the likelihood of termite infestation United States alone (over 2,500 species around the world), such as the traditional wood roof framing. most termite damage is attributed to subterranean termites. Subterranean termites nest in the ground because they Recently, much attention and concern has been directed to require a moist, humid environment to survive. Entry into the relative newcomer, the very aggressive Formosan termite, a building must be gained through a sheltered path, such found mainly in the southern states and Hawaii, but is dramatias a crack in a foundation wall or slab. If a sheltered path cally increasing in numbers and spreading toward the northern to the food source is not available, it is possible for termites states. In Southern Louisiana the population is estimated to have increased more than 3,000% in the past ten years alone. Concrete masonry is one of the best products available for termite resistance since it does not provide a source of nutrition. Entire structures can be constructed of concrete and masonry materials, virtually eliminating the possibility of damage from termites. This includes a composite block/steel bar joist floor system that is immune to termite attack (ref. 2). This TEK focuses on measures to reduce the possibility of subterranean termite entry into a building. While termites do not cause any Region I - Moderate to Region III - No Hazard damage to masonry materials, they to Light Hazard. Severe Hazard. do feed on any products containing cellulose, most notably wood. Region II - Light to Region IV - No Hazard. Moderate Hazard. Buildings that do not use wood or cellulose products as a construcNote: Local conditions may be more or less severe than indicated by the region classification. Such known local conditions should take tion material are not prone to terprecedence in determining the applicability of protective measures. mite infestation making concrete masonry the perfect application for both above and below grade Figure 1—Termite Infestation Potential construction. Concrete masonry is TEK 3-9A © 2000 National Concrete Masonry Association (replaces TEK 3-9)

86

to build their own access tunnels, which protect them from sunlight and open air. Often, these access tunnels can be the only direct sign of a termite infestation. It is important to consider the potential for termite infestation during the construction phase since the building construction practices themselves can help protect against future infestation. Many of these measures focus on proper design and quality construction to reduce possible entry routes and to provide a hostile (that is, dry) environment to ward off termites. These same methods may already be employed for protection from water penetration or soil gas entry. Strategies for termite control include: • building out of all concrete masonry; • minimizing cracks in walls and slabs; • sealing around all wall and floor penetrations; • adequate drainage around the foundation and adjacent soil; • providing access to inspect for termite tunnels; • installing barriers to prevent termite entry; • maintaining a minimum clearance between wood members and soil; • treating soil with chemicals to repel termites; and • utilizing termite resistant construction materials. The level of termite control employed on a particular job should be consistent with the expected severity of the termite hazard. This level of severity for a particular location can be determined from local experience or from the state entomological authorities. Where such information is not available, Figure 1 may serve as a guide. Site Conditions While preparing the site prior to construction, all roots, stumps, dead timber, and other wood debris should be removed from the site. Similarly, wood scraps from construction should be properly disposed. Leaving this material on site or in the backfill provides additional food sources for termites, attracting them and increasing the likelihood of infestation. Similarly, wood grade stakes or bracing stakes should be removed before or during a concrete placement and not be cast into the concrete. Leaving them in place attracts termites and provides a direct path for them through the concrete. Refer to Figure 2 for a summary of critical termite access areas. Backfilling with a free draining soil, incorporating a subgrade drainage system, and installing proper abovegrade water drainage will help keep the foundation and adjacent soil dry, providing a less hospitable environment for termites. In extreme circumstances, subterranean termites may not require constant access to and from the adjacent soil. Where conditions exist such that wood remains continuously wet, termites do not need to return to the soil to obtain water. However, such conditions are rare if proper design and construction for water penetration resistance are adhered to.

Key Notes 1 – Ensure that the soil directly adjacent to the foundation is dry and free of scrap lumber or decaying wood. 2 – All utility penetrations through foundation walls should be sealed for both termite and water penetration resistance. 3 – Remove any dead or decaying wood from the area. All trees and plants should be healthy. 4 – Any wood in direct contact with the ground should be rated for such use. Otherwise untreated or not naturally termite resistant wood provides a direct path for termite passage. 5 – Inspect the foundation at regular intervals for signs of termite activity or the development of cracks.

Figure 2—Concerns Regarding Termite Protection Reducing Entry Routes Once the termites have established a path, they have unimpeded access to the entire structure. Therefore, keeping termites out of the structure should always be the paramount objective. In addition to the obvious points of entry, such as wood in direct contact with the soil, other obscure (but critical) termite entry routes include: • through cracks in exposed wall faces or slabs. Termites are capable of moving through a crack only 1/32 inch (0.79 mm) wide; • direct access from soil under porches or patio slabs; • along the outside of pipes penetrating slabs or foundation walls; and • access tunnels on the interior or exterior of walls. Minimum Clearance to Soil It is desirable to keep wood elements as far as possible from the soil to minimize termite access. Nonstructural wood elements, such as wood siding and trim, should be kept a minimum of 6 inches (152 mm) from the soil surface. Structural wood framing, sill plates, and sheathing should be kept at least 8 inches (203 mm) above the soil, or as otherwise required by local building codes. However, if the nonstructural wood is in contact with the structural wood (which is generally the case), the 6 inch (152 mm) minimum clearance should be increased to 8 inches (203 mm). These general clearances do not apply 87

to pressure-treated wood or other termite and decay resistant woods. Minimizing Cracks Proper structural design of foundation walls, footings, and slabs will help prevent structural cracking that may allow termite entry. In addition to preventing cracks due to structural overload, cracking due to concrete shrinkage also needs to be addressed. Due to fluctuations in the temperature and moisture content, all materials have a tendency to expand and contract over time. With concrete masonry foundations, the primary concern focuses on shrinkage resulting in the development of tensile stresses. This is because the tensile strength of concrete is relatively small compared to the compressive strength; therefore shrinkage may result in small cracks within the masonry. It is normally not necessary to provide control joints in below grade residential concrete masonry basement walls. A control joint is a planned joint in a concrete masonry wall at regular intervals that accommodates shrinkage movement without unsightly, random cracking. The lack of a need for control joints is attributed to the relatively low range of thermal and moisture fluctuations occurring in below grade walls afforded by the soil adjacent to the walls and to the water resistant systems applied to basement walls. In most below grade basement wall construction, it is possible to provide a reinforced bond beam at or near the top of the wall in lieu of control joints to minimize crack development. The bond beam also provides a cap, preventing termites from coming up through the empty cores of ungrouted block and gaining entry into the building. Joint reinforcement embedded in the horizontal bed joints, usually at 16 inches on center, also provides additional tensile strength for the masonry and aids in crack control. It should be pointed out that horizontal reinforcement will not completely eliminate cracking, but it will hold the cracks so tightly together that the termites cannot get through. Additional measures to reduce the shrinkage cracking potential of concrete masonry include keeping the walls dry during construction. Because drying shrinkage is a primary cause of cracking in concrete masonry walls, it is important to minimize the potential for wetting concrete masonry during the construction process. At the jobsite, concrete block should be stored so as to protect the units from absorbing ground water or precipitation. This includes storing block on pallets (or otherwise isolating block from direct contact with the ground) and covering the units with plastic or other water-repellent materials. Concrete masonry units should be dry when laid. Some surface moisture is acceptable; however, saturated units should be allowed to dry out before placement in the wall. Concrete masonry units should never be wetted before or during placement in the wall, as may be customary with other types of masonry units. At the end of each workday, a weatherproof membrane should be placed over uncompleted walls to protect the units from rain or snow. Placing a board on top of the membrane

will help hold it in place and will prevent the membrane from sagging into the masonry cores and allowing water to collect. To limit concrete slab cracking, the recommendations of the American Concrete Institute (ref. 5) for quality concrete placement should be followed. In basement walls, the dampproofing and waterproofing measures employed to reduce water penetration aid in the prevention of termite entry. Waterproofing and dampproofing systems require that the barrier be continuous to prevent water penetration into voids or open seams. Similarly, the barrier is typically carried above the finished grade level to prevent water entry between the barrier and the foundation wall. Cracks exceeding 0.02 inches (0.5 mm) should be repaired before applying a waterproof or damp-proof barrier. However, the repair of hairline cracks is typically not required, as most barriers will either fill or span these small openings. In addition, waterproofing and dampproofing systems should be applied to clean dry walls. In all cases, manufacturer’s directions should be carefully followed for proper installation. Particular attention should be paid to reentrant corners at garages, porches, and fireplaces and to wall penetrations. Because stress concentrations develop at these intersections, pliable membranes and/or additional reinforcement are often recommended at these locations to span any potential cracks or hold them tightly together. Typical water penetration measures include coatings, sheet membranes, and drainage boards. Coatings are sprayed, trowelled, or brushed onto below-grade walls, providing a continuous barrier to water entry. Coatings should be applied to clean, structurally sound walls. Walls should be brushed or washed to remove dirt, oil, efflorescence, or other materials that may reduce the bond between the coating and the wall. Sheet membranes and panels (drainage boards) are less dependent on workmanship and on surface preparation than coatings. Many of the membrane systems are better able to remain intact in the event of settlement or other movement of the foundation wall. All seams, terminations, and penetrations must be properly sealed. Care must also be exercised during the backfilling process to ensure that the barrier is not damaged. In crawl space and stem walls, which typically are not treated on the exterior to prevent water entry as basement walls are, crack control measures become more important. In these cases, termites can enter the block through small cracks and move unseen up ungrouted cores. In these instances, solid grouting or capping of the walls is recommended. Capping Concrete Masonry Walls Various methods are used to seal the tops of masonry foundation walls. Should termites penetrate the face shell of a concrete masonry wall below, the cap prevents them from direct access to the wood superstructure. In reinforced construction, the masonry bond beam at the top of the wall serves as an effective cap, as shown in Figure 3. Bond beam units are specifically designed to accommo88

The Specification also requires enough water in the grout mixture to achieve a slump of 8 to 11 inches (203 to 279 mm) (ref. 6, 4) when tested in accordance with ASTM C 143 Standard Test FLOOR SHEATHING Method for Slump of Hydraulic Cement Concrete (ref. 9). See Figure 5. EXPOSEd WOOd FLOOR JOIST This high slump is contrary to the principles SHEATHING of cast-in-place concrete where high slump levels lead to reduced strengths and higher shrinkage. WOOd SILL Many engineers mistakenly try to apply this same CONTINUOUS REINFORCEMENT analogy to masonry – lowering the water content AS REQUIREd 8 in. (203 mm) in an effort to reduce shrinkage potential. HowMINIMUM FINISH BONd BEAM COURSE ever, in masonry construction, the high slump GRADE is critical as it allows the grout to be fluid enough GROUT STOP to flow around reinforcement and completely fill MATERIAL all the voids (ref. 3, 4, and 6). The initial high water-to-cement ratio is reduced significantly as the masonry units absorb the excess water, resulting in higher strengths and low shrinkage properties despite the high initial water-to-cement ratio. Additionally, as the excess water is absorbed into the masonry units, some of the cement is drawn into the unit with the water creating excellent bond and reducing the formation of voids. Figure 3—Masonry Bond Beam Cap Grout should also be placed in lifts not exceeding 5 ft. (ref. 6). A lift is the layer of grout date horizontal reinforcement and grout as shown in Figure 4. placed in a single continuous operation. AdditionBond beam units can be either solid bottom or open bottom. ally, each lift should be consolidated with either a 3/4 in. (19 The latter requires a screen grout stop or expanded metal mm) diameter low velocity vibrator. Consolidation eliminates to contain the grout within the unit. A reinforced bond beam voids, helping to ensure complete grout fill and good bond is preferred to solid units or solid bottom units with solid with the masonry units. After the water is absorbed from the head joints since the reinforcement in bond beams will hold grout mixture into the masonry (normally 3 to 10 minutes any cracks that form tightly together to prevent termite entry after placement, depending on the absorption characteristics through the cracks. of the unit and weather conditions), the grout should be re Proper grouting procedures are important to ensure bond consolidated to close the space left by the excess water that with the masonry units and void free areas in bond beams and was absorbed (ref. 3). In any case, reconsolidation must be cells to be filled. Grout should conform to the Specification completed before the grout loses its plasticity. for Grout for Masonry, ASTM C 476 (ref. 7) or be specified Metal termite shields may be installed as a continuous to have a minimum compressive strength of 2,000 psi (13.8 barrier directly below the sill plate. If infestation occurs, terMPa) at 28 days in accordance with the Specification for mites are forced to build conspicuous access tunnels around Masonry Structures, ACI 530.1/ASCE 6/TMS 402 (ref. 6). the shield, making detection easy. Because termites require only a 1/32 inch (0.79 mm) gap for penetration, termite shields must be installed with great care to be effective. All seams must be soldered and all openings around anchor bolts and service lead-ins must be sealed. Because of the extreme care required to provide an impenetrable metal termite shield, they generally are not to be relied on for termite protection.

CLOSEd BOTTOM Closed bottom

OPEN BOTTOM Open bottom

Figure 4—Bond Beam Units for Reinforced Construction

Exterior Insulation The rigid plastic foams that are often used to insulate crawl space and the exterior side of basement walls can allow termites to create undetectable tunnels and is prohibited for such use by some codes (ref. 7). An advantage of concrete masonry foundation walls is their ability to accommodate 89

4 in. (102 mm)

Additional Considerations for Crawl Spaces Figure 6 illustrates termite control measures for crawl space foundations. Crawl space floors should be kept at or above the exterior finished grade to facilitate drainage in the crawl space. Where this is not possible, or on sites where water flows toward the building due to the site slope, area drains should be installed. Unless specified otherwise by local codes, wood girders should be at least 12 inches (305 mm) above the crawl space floor, and wood joists should be no closer than 18 inches (457 mm) to the soil. In all cases, enough clearance should be maintained to allow access to the crawl space for inspection.

8 TO 11 in. (203 TO 279 mm) SLUMP

12 in. (305 mm) CONE

Chemical Treatments

8 in. (203 mm)

Figure 5—Masonry Requires a Fluid Grout; Slump to be between 8 and 11 in. (ref. 6)

insulation within the cores of the masonry units where it is protected from direct contact with the soil. Either rigid foam insulation inserts, granular fill insulation, or foamed-in-place insulation can be used for this purpose.

Numerous methods are available to create a pesticide barrier within the soil adjacent to a structure to prevent termite entry. Soil treatment before or during construction is often most effective as there is better access to the subgrade soil. If a slab-on-grade is also going to be used, the soil under the slab can also be pretreated. While post-construction treatment is far more common, it is also more difficult. Limited access to some areas may not allow for an effective chemical barrier to be established.

FLOOR SHEATHING EXPOSEd WOOd SHEATHING

FINISH GRADE

8 in. (203 mm) MINIMUM

FLOOR JOIST

WOOD GIRDER 18 in. (457 mm) MINIMUM 24 in. (610 mm) dESIRABLE 12 in. (305 mm) MININUM

DESIRED GRADE LEVEL OPTIONAL FOOTING DRAIN WHERE CRAWL SPACE GRADE IS BELOW EXTERIOR GROUND LEVEL

REINFORCING STEEL AS REQUIREd OPTIONAL AREA dRAIN AT LOW POINT

Figure 6—Termite Control Measures for Crawl Space Foundations 90

Conclusion Concrete masonry is an ideal construction material to resist termites. It does not provide food to attract them, and provides a barrier to prevent termite entry. It is also very versatile

with an almost endless amount of architectural shapes, sizes, textures, and colors available. An innovative, totally termite proof concrete masonry floor system utilizing a hidden steel bar joist supporting system is also available.

References 1. Basement Manual, TR-68B. National Concrete Masonry Association, 2000 2. Concrete Masonry Homes: Recommended Practices. U.S. Department of Housing and Urban Development, Office of Policy Development and Research, 1999. 3. Grouting Concrete Masonry Walls, NCMA TEK 3-2. National Concrete Masonry Association, 1997. 4. Grout for Concrete Masonry, NCMA TEK 9-4. National Concrete Masonry Association, 1998. 5. Guide to Residential Cast-In-Place Concrete Construction, ACI 332-84. American Concrete Institute, 1984. 6. Specification for Masonry Structures, ACI 530.1-99/ASCE 6-99/TMS 602-99. Reported by the Masonry Standards Joint Committee, 1999. 7. Standard Building Code. Southern Building Code Congress International, 1999: 2304.1.4. 8. Standard Specification for Grout for Masonry, ASTM C 476-99. American Society for Testing and Materials, 1999. 9. Standard Test Method for Slump of Hydraulic Concrete, ASTM C 143/C 143M. American Society for Testing and Materials, 1998

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METRIC CONCRETE MASONRY CONSTRUCTION


Keywords: construction, dimensions, hard metric, metric, metric conversion, modular coordination, soft metric METRIC UNITS

INTRODUCTION The metric system (Systeme Internationale or SI system) is the standard international system of measurement, and the system that has been mandated by the Metric Conversion Act (ref. 1) for use in the construction of all United States Federal buildings. Essentially, the Metric Conversion Act requires building designs and construction drawings to be submitted in metric units and constructed according to metric specifications. The subsequent Savings in Construction Act of 1996 (ref. 5) places strong limitations for Federal agencies requiring hard metric concrete masonry units and allows conventional concrete masonry units to be used in metric construction projects. Economical adjustments that have virtually no impact on the configuration of the final project can be made to accommodate inch-pound units on a job where the plans and specifications are in metric, as described here and in Metric Design Guidelines for Concrete Masonry Construction (ref. 3). Complying with these government mandates requires a knowledge of the metric system of measurement and its conventions as well as an understanding of how construction materials, such as concrete masonry, are best incorporated into a metric building design.

Table 1—Metric Decimal Prefixes

Prefix milli centi deci deca hecto kilo mega

Symbol m c d da h k M

Order of magnitude 10-3 10-2 10-1 10 102 103 106

Expression one thousandth, 0.001 one hundredth, 0.01 one tenth, 0.1 ten, 10 one hundred, 100 one thousand, 1000 one million, 1,000,000

The metric system uses several base units of measurement with various prefixes that indicate magnitude. For example, the base unit for length is the meter. When combined with the prefix kilo—meaning one thousand—the unit of measurement is kilometer (km), meaning one thousand meters. Table 1 lists the metric decimal prefixes and their magnitudes. Just as the inch-pound system has preferred units of measurement (i.e., building dimensions are measured in feet, not in yards), the metric system also conforms to a preferred set of units. For design and construction in the United States, typically only the prefixes milli and kilo are used. For example, lengths are given in millimeters, meters, or kilometers, not in centimeters or hectometers. Table 2 lists common inch-pound units used in building design and construction, their standard metric unit equivalents, and conversion factors. The metric units listed in Table 2 are the preferred units. As with any form of communication, there are some basic rules that apply to the use of the metric system so that the meaning is consistent and clear, thereby minimizing the potential for errors during construction. The following sections summarize common metric conventions. Abbreviations The third column of Table 2 indicates the proper abbreviations for metric units. Note the use of capital and lower case letters. For example, megapascal is abbreviated MPa. If mPa were written instead, it would indicate millipascals rather than megapascals. Symbols When using inch-pound units, the use of symbols to represent feet (') and inches (") is second nature. No such symbols are used in the metric system; only the abbreviations listed in Table 2. Stating Metric Units While mixing feet and inches is common practice, a similar practice is not used in the metric system. For example, if dual units are shown on a set of plans, the metric equivalent of 8' 92


(2008)

- 8" would be 2.64 m, not 2.4 m - 203 mm. In addition, fractions are never used in the metric system, decimals are used instead. For example, a length of nine and one-half meters is written as 9.5 m, not as 9 1/2 m. Rounding Dimensions on building plans are rarely shown to less than 1/8 in. (3 mm) because it is impractical to build to a tighter tolerance. Similarly, it is meaningless to state dimensions in decimals of millimeters. For example, a required tolerance of +3/8 in. thick becomes +10 mm, rather than + 9.5 mm. SOFT VERSUS HARD METRIC CONVERSION The most common consequence of the metric conversion effort has been a simple relabeling of products with equivalent metric dimensions, with no physical change to the product dimensions. This is commonly called soft metric conversion.

From a practical standpoint, soft metric conversion is easily accomplished. For soft metric conversion of concrete masonry, the metric equivalents of concrete masonry unit dimensions are simply the exact metric conversions of the inch-pound unit dimensions. Table 3 lists the inch-pound and metric equivalent dimensions for typical concrete masonry units of various sizes. Hard metric conversion means the product is resized to metric modular dimensioning. Hard metric conversion is principally applied to modular products where dimensional tolerances are critical. Hard metric concrete masonry units are manufactured to nominal widths of 100, 150, 200, 250, and 300 mm, nominal heights of 100 and 200 mm, and nominal lengths of 200 and 400 mm. Specified dimensions are 10 mm smaller than nominal to provide space for vertical and horizontal mortar joints. The difference between soft and hard metric concrete masonry units is shown in Figure 1.

Table 2—Inch-Pound To Metric Conversions Quantity Length

Area

Volume

Mass Mass density Force Force per unit length Force per unit area Bending moment Thermal resistance (R-Value) Thermal conductance (U-Factor) Temperature

to convert from these inch-pound units. . . mile (mi) foot (ft) foot (ft) inch (in.) square yard (yd2) square foot (ft2) square inch (in.2) cubic yard (yd3) cubic foot (ft3) cubic inch (in.3) pound (lb) kip (k) pounds/cubic foot (lb/ft3 or pcf) pound (lb) kip (k) pound/foot (lb/ft or plf) kip/foot (k/ft) pound/square inch (lb/in.2 or psi) kip/square inch (k/in.2 or ksi) pound/square foot (lb/ft2 or psf) foot-pound (ft-lb) foot-kip (ft-k) inch-pound per foot (in.-lb/ft) square foot-hourdegree Fahrenheit/British thermal unit (ft2-h-oF/Btu) British thermal unit/square foothour-degree Fahrenheit (Btu/h-ft2-oF) degrees Fahrenheit (oF) degrees Fahrenheit (oF)

to these metric units. . . kilometer (km) meter (m) millimeter (mm) millimeter (mm) square meter (m2) square meter (m2) square millimeter (mm2) cubic meter (m3) cubic meter (m3) cubic millimeter (mm3) kilogram (kg) metric ton (t) kilogram/cubic meter (kg/m3) newton (N) kilonewton (kN) newton/meter (N/m) kilonewton/meter (kN/m) megapascal (MPa) megapascal (MPa) pascal (Pa) newton . meter (N. m) kilonewton . meter (kN. m) newton . meter per meter (N.m/m) square meter . degree Kelvin/ Watt (m2 . K/W) Watt/square meter . degree Kelvin (W/m2 . K) degrees Celsius (oC) degrees Kelvin (K)

multiply the inch-pound units by: 1.609344 0.3048 304.8 25.4 0.83612736 0.09290304 645.16 0.764555 0.0283168 16,367.064 0.453592 0.453592 16.0185 4.44822 4.44822 14.5939 14.5939 0.00689476 6.89476 47.8803 1.35582 1.35582 0.370686 0.176

5.678 o

C = (oF - 32)/1.8 K = (oF + 459.67)/1.8

Example: The specified length of a concrete masonry unit is typically 155/8 in. To convert this length to millimeters, use the conversion factor 25.4. The converted actual length = 15.625 x 25.4 = 397 mm. 93

Table 3—Typical Concrete Masonry Unit Dimensions Nominal unit size Inch-pound Soft metric (in.) (mm) 4 x 8 x 16 102 x 203 x 406 6 x 8 x 16 152 x 203 x 406 8 x 8 x 16 203 x 203 x 406 10 x 8 x 16 254 x 203 x 406 12 x 8 x 16 305 x 203 x 406 (a)

Specified unit size Faceshell thickness(a) Web thickness(a) Inch-pound Soft metric Inch-pound Soft metric Inch-pound Soft metric (in.) (mm) (in.) (mm) (in.) (mm) 3 3 3 5/8 x 7 5/8 x 15 5/8 92 x 194 x 397 /4 19 /4 19 5 5/8 x 7 5/8 x 15 5/8 143 x 194 x 397 1 25 1 25 7 5/8 x 7 5/8 x 15 5/8 194 x 194 x 397 1 1/4 32 1 25 9 5/8 x 7 5/8 x 15 5/8 244 x 194 x 397 1 3/8 35 1 1/8 29 11 5/8 x 7 5/8 x 15 5/8 295 x 194 x 397 1 1/2 38 1 1/8 29

Dimensions are minimums required by Standard Specification for Loadbearing Concrete Masonry Units (ref. 4). 7 5/8 in. (194 mm) 7 5/8 in. (194 mm)

15 5/8 in. (397 mm) "Soft Metric" CMU 190 mm (7.5 in.) 190 mm (7.5 in.)

390 mm (15.4 in.) "Hard Metric" CMU

Figure 1—Specified Dimensions of Soft and Hard Metric Concrete Masonry Units MODULAR COORDINATION Modular design is based on the use of standardized components, which helps increase the efficiency and cost-effectiveness of construction. Modular components are massproduced to exacting physical properties and dimensions. Modular products are based on a 4-in. (102-mm) module in the inch-pound system and a 100-mm (3.9-in.) module in the metric system. Since 4 inches equals 101.6 mm, the inchpound module is 1.6 percent larger than the 100 mm metric module. This seemingly small difference (about 1/16 in. or 1.5 mm), however is cumulative, becoming 1/4 in. in 16 in. and 3 /4 in. in 4 ft (6 mm in 406 mm and 19 mm in 1.2 m), making the two modules incompatible. When modular units are placed, they produce wall lengths, heights and thicknesses that are multiples of the given module. This allows building dimensions and wall openings to be placed and sized to minimize cutting on site. However, when units of different modular dimensions are incorporated into the same wall, such as an 8-in. (203-mm) concrete masonry unit in a wall laid out on a 100-mm module, significant coordination and adjustment is needed.

When hard metric concrete masonry units are available for a metric project, modular coordination is straightforward, as the building is laid out on a 100-mm module, which corresponds to the nominal dimensions of the hard metric masonry units. When hard metric concrete masonry units are not available for a metric job, two options are available: lay out the building using inch-pound modules, which are then converted to their metric equivalents, or use soft metric concrete masonry units in a building laid out using a 100-mm module. These are described in more detail below. Metric Design Based on Soft Metric Building Modules This option essentially applies a soft metric conversion to the project plans and specifications. From the beginning of the project, a module of 101.6 mm, rather than 100 mm, is used. In this case, soft metric concrete masonry units can be used without further adjustment. Structures designed based on soft metric conversions should incorporate windows and doors sized to the inch-pound module as well. The width of an opening in a concrete masonry wall should be a multiple of 8 in. (203 mm) plus the width of one mortar joint ( 3/8 in. or 10 mm). The height of the opening should be a multiple of 8 in. (203 mm). For example, a nominal 4 ft x 4 ft (1,219 x 1,219 mm) opening should have actual dimensions of 4 ft - 3/8 in. x 4 ft (1,229 x 1,219 mm). Similarly, the width of piers should be a multiple of 8 in. (203 mm) minus the width of one mortar joint ( 3/8 in. or 10 mm). Soft Metric Units Used With Hard Metric Building Modules This option uses soft metric concrete masonry units in a project laid out using 100-mm modules. Because soft metric units are approximately 2% larger in height and length than hard metric units, complications arise when they are incorporated into a structure designed according to the 100 mm module, or when other modular metric components, such as windows and doors, are not readily available. Because soft metric units are longer, cutting around openings will be required. Cutting around door and window openings can be avoided by substituting soft metric door and window units in the masonry. Cutting can also be minimized by moving one side of the opening to the nearest inch-pound modular dimension, eliminating the need to cut units on both sides of the opening. Vertical coursing can be adjusted by either of the two 94

methods illustrated in Figure 2. The first method (Case A) is to use soft metric concrete masonry units with a 3/8 in. (10 mm) mortar joint and allow each story to be slightly taller than specified. For example, consider a specified story height of 13 courses (2600 mm, 8 ft - 6 3/8 in.). Using soft metric units, the story height would increase to 2641 mm (8 ft - 8 in.), an increase of 1 5/8 in. (41 mm) per story height. The second method (Case B) uses custom soft metric concrete masonry units manufactured to an actual height of 7 1/2 in. (191 mm) rather than 7 5/8 in. (194 mm) (unit height is more easily adjusted during manufacture than is unit length). In the example given above, the metric module is maintained for the entire wall height when 7 1/2 in. (191 mm) high units are used with standard 3/8 in. (10 mm) horizontal mortar joints. For more information on using soft metric units in 100-mm module construction, see Metric Design Guidelines for Concrete Masonry Construction (ref. 3).

193.7 193.7 193.7 193.7 193.7 193.7 193.7 193.7 193.7 193.7 193.7 193.7 193.7 Case A

Story Height = 2,641 mm = 8 ft - 8 in. 190.5 190.5 190.5 Standard 190.5 soft metric units 190.5 190.5 3 Joints = / 8 in. (9.5 mm) 190.5 190.5 190.5 190.5 190.5 190.5 190.5

Story Height = 2,600 mm = 8 ft - 6 3 /8 in. Custom 7 1/ 2 in. high soft metric units

3

Joints = /8 in. (9.5 mm)

Case B

Figure 2—Vertical Coursing With Inch-Pound Concrete Masonry Units (ref. 3)

REFERENCES 1. 2. 3. 4. 5.

Metric Usage in Federal Government Programs, Executive Order 12770, 1991. Metric Guide for Federal Construction, First Edition. Washington, DC: National Institute of Building Sciences, 1991. Metric Design Guidelines for Concrete Masonry Construction, TR 172. National Concrete Masonry Association, 2000. Standard Specification for Loadbearing Concrete Masonry Units, ASTM C 90-03. ASTM International, 2003. Savings in Construction Act of 1996, Public Law 104-298, 1996.

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CONCRETE MASONRY BASEMENT WALL CONSTRUCTION Keywords: basements, basement wall, bracing, construction details, construction techniques, corners, details, foundation walls, grout, insulation, mortar, plain concrete masonry, reinforced concrete masonry, surface bonding, unreinforced concrete masonry, waterproofing INTRODUCTION Basements allow a building owner to significantly increase usable living, working, or storage space at a relatively low cost. Old perceptions of basements have proven outdated by stateof-the-art waterproofing, improved drainage systems, and natural lighting features such as window wells. Other potential benefits of basements include room for expansion of usable space, increased resale value, and safe haven during storms. Historically, plain (unreinforced) concrete masonry walls have been used to effectively resist soil loads. Currently, however, reinforced walls are becoming more popular as a way to use thinner walls to resist large backfill pressures. Regardless of whether the wall is plain or reinforced, successful performance of a basement wall relies on quality construction in accordance with the structural design and the project specifications.

TEK 3-11 Construction

(2001)

MATERIALS Concrete Masonry Units Concrete masonry units should comply with Standard Specification for Loadbearing Concrete Masonry Units, ASTM C 90 (ref. 8). Specific colors and textures may be specified to provide a finished interior to the basement. Drywall can also be installed on furring strips, if desired. A rule of thumb for estimating the number of concrete masonry units to order is 113 units for every 100 ft2 (9.3 m2) of wall area. This estimate assumes the use of 3/8 in. (9.5 mm) mortar joints. Mortar Mortar serves several important functions in a concrete masonry wall; it bonds the units together, seals joints against air and moisture penetration, and bonds to joint reinforcement, ties, and anchors so that all components perform as a structural element. Mortar should comply with Standard Specification for Mortar for Unit Masonry, ASTM C 270 (ref. 9). In addi-

Table 1—Mortar Proportions by Volume (Ref. 12) Proportions by volume (cementitious materials) Portland cement or Masonry cement Mortar cement Mortar Type blended cementa M S N M S N Cement- M 1 — — — — — — lime S 1 — — — — — — N 1 — — — — — — O 1 — — — — — —Mortar M 1 — — — — — 1 cement M — --- — — 1 — — 1/2 S — — — — — 1 S — — — — — 1 — N — — — — — — 1 Masonry M 1 — — 1 — — — cement M — 1 — — — — — 1/2 S — — 1 — — — S — — 1 — — — — N — — — 1 — — — O — — — 1 — — — 1

Hydrated lime or lime puttya 1/4 over 1/4 to 1/2 over 1/2 to 11/4 over 11/4 to 21/2 — — — — — — — — — — —

Aggregate measured in a damp, loose condition Not less than 21/4 and not more than 3 times the sum of the separate volumes of cementitious materials.

When plastic cement is used in lieu of portland cement, hydrated lime or putty may be added, but not in excess of one tenth of the volume of cement.

96


tion, most building codes require the use of Type M or S mortar for construction of basement walls (refs. 2, 4, 5, 9, 13), because Type M and S mortars provide higher compressive strengths. Table 1 lists mortar proportions. Typical concrete masonry construction uses about 8.5 ft3 (0.24 m3) of mortar for every 100 ft2 (9.3 m2) of masonry wall area. This figure assumes 3/8 in. (9.5 mm) thick mortar joints, face shell mortar bedding, and a 10% allowance for waste. Grout In reinforced concrete masonry construction, grout is used to bond the reinforcement and the masonry together. Grout should conform to Standard Specification for Grout for Masonry, ASTM C 476 (ref. 10), with the proportions listed in Table 2. As an alternative to complying with the proportion requirements in Table 2, grout can be specified to have a minimum compressive strength of 2000 psi (13.8 MPa) at 28 days. Enough water should be added to the grout so that it will have a slump of 8 to 11 in. (203 to 279 mm). The high slump allows the grout to be fluid enough to flow around reinforcing bars and into small voids. This initially high water-to-cement ratio is reduced significantly as the masonry units absorb excess mix water. Thus, grout gains high strengths despite the initially high water-to-cement ratio. Table 2—Grout Proportions by Volume (Ref. 10)

Type Fine Grout

Coarse Grout

Proportions by volume (cementitious materials) portland hydrated cement or lime or blended cement lime putty 1

0 to 1/10

1

0 to 1/10

Aggregate measured in a damp, loose condition Fine Coarse 2¼ to 3 times the sum of the volumes of the cementitious materials 2¼ to 3 times the sum of the volumes of cementitious materials

1 to 2 times the sum of the volumes of cementitious materials

CONSTRUCTION Prior to laying the first course of masonry, the top of the footing must be cleaned of mud, dirt, ice or other materials which reduce the bond between the mortar and the footing. This can usually be accomplished using brushes or brooms, although excessive oil or dirt may require sand blasting. Masons typically lay the corners of a basement first so that alignment is easily maintained. This also allows the mason to plan where cuts are necessary for window openings or to fit the building’s plan. To make up for surface irregularities in the footing, the first course of masonry is set on a mortar bed joint which can range from 1/4 to 3/4 in. (6.4 to 19 mm) in thickness. This initial bed joint should fully bed the first course of masonry units, although mortar should not excessively protrude into cells that will be grouted.

All other mortar joints should be approximately 3/8 in. (9.5 mm) thick and, except for partially grouted masonry, need only provide face shell bedding for the masonry units. In partially grouted construction, webs adjacent to the grouted cells are mortared to restrict grout from flowing into ungrouted cores. Head joints must be filled solidly for a thickness equal to a face shell thickness of the units. Tooled concave joints provide the greatest resistance to water penetration. On the exterior face of the wall, mortar joints may be cut flush if parging coats are to be applied. When joint reinforcement is used, it should be placed directly on the block with mortar placed over the reinforcement in the usual method. A mortar cover of at least 5/8 in. (15.9 mm) should be provided between the exterior face of the wall and the joint reinforcement. A mortar cover of 1/2 in. (12.7 mm) is needed on the interior face of the wall. For added safety against corrosion, hot dipped galvanized joint reinforcement is recommended. See Figures 1-4 for construction details. Reinforced Masonry For reinforced masonry construction, the reinforcing bars must be properly located to be fully functional. In most cases, vertical bars are positioned towards the interior face of basement walls to provide the greatest resistance to soil pressures. Bar positioners at the top and bottom of the wall prevent the bars from moving out of position during grouting. A space of at least 1/2 in. (12.7 mm) for coarse grout and 1/4 in. (6.4 mm) for fine grout should be maintained between the bar and the face shell of the block so that grout can flow completely around the reinforcing bars. As mix water is absorbed by the units, voids can form in the grout. Accordingly, grout must be puddled or consolidated after placement to eliminate these voids and to increase the bond between the grout and the masonry units. Most codes permit puddling of grout when it is placed in lifts less than about 12 in. (305 mm). Lifts over 12 inches (305 mm) should be mechanically consolidated and then reconsolidated after about 3 to 10 minutes. Surface Bonding Another method of constructing concrete masonry walls is to dry stack units (without mortar) and then apply surface bonding mortar to both faces of the wall. The surface bonding mortar contains thousands of small glass fibers. When the mortar is applied properly to the required thickness, these fibers, along with the strength of the mortar itself, help produce walls of comparable strength to conventionally laid plain masonry walls. Surface bonded walls offer the benefits of excellent dampproof coatings on each face of the wall and ease of construction. Dry-stacked walls should be laid in an initial full mortar bed to level the first course. Level coursing is maintained by using a rubbing stone to smooth small protrusions on the block surfaces and by inserting shims every two to four courses. Water Penetration Resistance Protecting below grade walls from water entry involves installation of a barrier to water and water vapor. An imper97

19 18

17

12 7 5 6 1

4 3 9

15 11

14

2

10

13 8

16

1. Concrete masonry units, typically 8-in. units. Larger sizes may be required in for some soil and backfill height conditions. 2. Mortar, generally Type S. Joints should be tooled for improved impermeability unless the exterior side is parged. 3. Vertical reinforcing bars, if required. Reinforcement should be placed adjacent to openings, in corners and at a maximum spacing determined from a structural analysis. Positioners hold the vertical bars in proper position. 4. Joint reinforcement or horizontal reinforcing bars to aid in control of shrinkage cracking and in Seismic Design Categories C, D, E, and F. See TEK 14-18 (ref. 7) for more information on seismic reinforcement requirements. 5. Grout of 2,000 psi (13.8 MPa) minimum compressive strength in cores containing reinforcement. Consolidate grout by puddling or vibration to reduce voids. 6. Solid grouted and reinforced top course to distribute loads from the walls above and increase soil gas and insect resistance. 7. Anchor bolts. Typically 7 in. (178 mm) long, 1/2 in. (12.7 mm) diameter anchor bolts are spaced no more than 4 ft (1.2 m) on center. Anchor bolts significantly increase earthquake and high wind resistance. 8. Concrete footing. Footings distribute loads to the supporting soil. Concrete should have a minimum strength of 2500 psi (17.2 MPa) and be at least 6 in. (152 mm) thick, although many designers prefer footings to be as thick as the wall thickness and twice as wide as the wall thickness. Incorporating two #4 bars (or larger) increases the ability to span weak spots. 9. Concrete slab, typically minimum 2500 psi (17.2 MPa), 4 in. (101 mm) thick. Contraction joint spacing should not exceed about 15 ft (4.6 m). Welded wire fabric located near the center of the slab increases strength and holds unplanned shrinkage cracks tightly together. Welded wire fabric should be cut at contraction joints. 10. Aggregate base. A 4 to 6 in. (102 to 152 mm) base of washed aggregate (3/4 to 11/2 in. (19 to 38 mm) diameter) distributes slab loads evenly to the underlying soil, provides a level, clean surface for slab placement, and allows for inclusion of a soil gas depressurization system. 11. Vapor retarder. Continuous or lapped sheets of 6 mil (152 mm) polyethylene, PVC or equivalent reduce rising dampness and block soil gas infiltration through the slab. Vapor retarders can be placed on top of the aggregate base to increase the effectiveness of the soil gas barrier system, or under the aggregate to reduce concrete placement and curing difficulties. 12. Waterproof or dampproof membrane. Dampproof where hydrostatic pressure will not occur. Where ground water levels are high, soil drainage is slow, or where radon gas levels are high, consideration of waterproof membranes such as rubberized asphalt, polymer-modified asphalt, butyl rubber and/or drainage boards should be considered. 13. Foundation drain. Perforated pipe collects and transports ground water away from the basement. Drains should be located below the top of the slab and should be sloped away from the building to natural drainage, a storm water sewer, or a sump. 14. Free draining backfill. At least 12 in. (305 mm) of washed gravel or other free draining backfill material should be placed around drains to facilitate drainage. Cover the top of the gravel with a filtering geotextile to prevent clogging. 15. Backfill. Backfill should be placed after wall has gained sufficient strength and is properly braced or supported. 16. Undisturbed soil. Soil beneath footings and slabs should be undisturbed or compacted. 17. Top of grade. Surrounding soil should slope away from building to drain water away from walls. The top 4 to 8 in. (102 to 203 mm) of soil should be of low permeability so that water is absorbed slowly into the soil. 18. Floor diaphragm. A floor diaphragm supports the tops of masonry walls and distributes loads from the superstructure to them. 19. Flashing. Flashing should be installed at the top of basement walls to prevent water from entering the wall. Figure 1— Basement/Foundation Wall (Ref. 1) 98

1 3 4 5

12 15

9 10

Alternate Courses

14 13

2 8

11

16

Figure 2—Typical Footing Detail (Ref. 1)

(A) 8-in. to 8-in. (203 to 203 mm) Wall Corner Detail

Alternate Courses

18 19

Solid 2 x 6 x 8 in. (51 x 153 x 203 mm)

7 17

6

1 2 5

(B) 10-in. to 10-in. (254 to 254 mm) Wall Corner Detail

4 15

3

Figure 3—Typical Floor Connection (Ref. 1)

vious barrier on the exterior wall surface can prevent moisture entry. The barrier is part of a comprehensive system to prevent water penetration, which includes proper wall construction and the installation of drains, gutters, and proper grading. Building codes (refs. 2, 4 , 5, 9, 13) typically require that basement walls be dampproofed for conditions where hydrostatic pressure will not occur, and waterproofed where hydrostatic pressures may exist. Dampproofing is appropriate where groundwater drainage is good, for example where granular backfill and a subsoil drainage system are present. Hydrostatic pressure may exist due to a high water table, or due to poorly draining backfill, such as heavy clay soils. Materials used for waterproofing are generally elastic, allowing them to span small cracks and accommodate minor movements. When choosing a waterproof or dampproof system, consideration should be given to the degree of resistance to hydrostatic head of water, absorption characteristics, elasticity, stability in moist soil, resistance to mildew and algae, impact or puncture resistance, and abrasion resistance. A complete discussion of waterproofing, dampproofing, and drainage systems is included in TEK 19-3A (ref. 6). All dampproofing and waterproofing systems should be applied to walls that are clean and free from dirt, mud

Alternate Courses

Solid 4 x 4 x 8 in. (102 x 102 x 203 mm)

(C) 12-in. to 12 in. (305 to 305 mm) Wall Corner Detail

Figure 4—Standard Corner Layout Details

and other materials which may reduce bond between the coating and the concrete masonry wall. Draining water away from basement walls significantly reduces the pressure the walls must resist and reduces the possibility of water infiltration into the basement if the waterproofing (or dampproofing) system fails. Perforated pipe has historically proven satisfactory when properly installed. When placed on the exterior side of basement walls, perforated pipes are usually laid in crushed stone to facilitate drainage. To prevent migration of fine soil into the drains, filter fabrics are often placed 99

over the gravel. Drainage pipes can also be placed beneath the slab and connected into a sump. Pipes through the footing or the wall drain water from the exterior side of the basement wall. The drainage and waterproofing systems should always be inspected prior to backfilling to ensure they are adequately placed. Any questionable workmanship or materials should be repaired at this stage since repairs are difficult and expensive after backfilling.

Ensure water/dampproofing or drainage systems and bracing are properly in place prior to backfilling 2x10 in. (51x254 mm) plank vertical brace

2x4 in. (51x102 mm) cleat 2x4 in.

Two 2x6 in. (51x152 mm) stakes driven into firm soil at least

Backfilling (51x102 mm) brace strut One of the most crucial aspects of basement construction is how and when to properly backfill. Walls should be properly braced Figure 5—Typical Bracing for Concrete Masonry Basement or have the first floor in place prior to backfilling. Otherwise, a wall which is designed to a. Variation from level: bed joints................................. be supported at the top may crack or even fail from the +1/4 in. (6.4 mm) in 10 ft (3.1 m), +1/2 in. (12.7 mm) max large soil pressures. Figure 5 shows one bracing scheme top surface of bearing walls.................................... which has been widely used for residential basement walls. +1/4 in.(6.4 mm), +3/8 in.(9.5 mm), +1/2 in.(12.7mm) max More substantial bracing may be required for high walls b. Variation from plumb...........+1/4 in. (6.4 mm) 10 ft (3.1 m) or large backfill pressures. ...........................+3/8 in. (9.5 mm) in 20 ft (6.1 m) The backfill material should be free-draining soil with.................................+1/2 in. (12.7 mm) maximum out large stones, construction debris, organic materials, c. True to a line..............+1/4 in. (6.4 mm) in 10 ft (3.1 m) and frozen earth. Saturated soils, especially saturated clays, ...........................+3/8 in. (9.5 mm) in 20 ft (6.1 m) should generally not be used as backfill materials since .................................+1/2 in. (12.7 mm) maximum wet materials significantly increase the hydrostatic presd. Alignment of columns and bearing walls (bottom versure on the walls. sus top)......................................+1/2 in (12.7 mm) Backfill materials should be placed in several lifts 4. Location of elements and each layer should be compacted with small mechania. Indicated in plan...........+1/2 in (12.7 mm) in 20 ft (6.1 m) cal tampers. Care should be taken when placing the back...................................+3/4 in. (19.1 mm) maximum fill materials to avoid damaging the drainage, waterb. Indicated in elevation proofing or exterior insulation systems. Sliding boul.............................+1/4 in. (6.4 mm) in story height ders and soil down steep slopes should thus be avoided .................................+3/4 in. (19.1 mm) maximum since the high impact loads generated can damage not only the drainage and waterproofing systems but the wall Insulation as well. Likewise, heavy equipment should not be operThe thermal performance of a masonry wall depends ated within about 3 feet (0.9 m) of any basement wall on its R-value as well as the thermal mass of the wall. Rsystem. value describes the ability to resist heat flow; higher R-values The top 4 to 8 in. (102 to 203 mm) of backfill mategive better insulating performance. The R-value is rials should be low permeability soil so rain water is determined by the size and type of masonry unit, type and absorbed into the backfill slowly. Grade should be sloped amount of insulation, and finish materials. Depending on away from the basement at least 6 in. (152 mm) within the particular site conditions and owner’s preference, 10 feet (3.1 m) of the building. If the ground naturally insulation may be placed on the outside of block walls, in slopes toward the building, a shallow swale can be inthe cores of hollow units, or on the interior of the walls. stalled to redirect runoff. Thermal mass describes the ability of materials like concrete masonry to store heat. Masonry walls remain warm or Construction Tolerances cool long after the heat or air-conditioning has shut off, keepSpecifications for Masonry Structures (ref. 8) speciing the interior comfortable. Thermal mass is most effective fies tolerances for concrete masonry construction. These when insulation is placed on the exterior or in the cores of tolerances were developed to avoid structurally impairthe block, where the masonry is in direct contact with the ing a wall because of improper placement. interior conditioned air. 1. Dimension of elements in cross section or elevation Exterior insulated masonry walls typically use rigid board ......................-1/4 in. (6.4 mm), +1/2 in. (12.7 mm) insulation adhered to the soil side of the wall. The insula2. Mortar joint thickness: bed............+1/8 in. (3.2 mm) tion requires a protective finish where it is exposed above head...................-1/4 in (6.4 mm), +3/8 in. (9.5 mm) grade to maintain durability, integrity, and effectiveness. 3. Elements 100

Concrete masonry cores may be insulated with molded polystyrene inserts, expanded perlite or vermiculite granular fills, or foamed-in-place insulation. Inserts may be placed in the cores of conventional masonry units, or they may be used in block specifically designed to provide higher R-values. Interior insulation typically consists of insulation installed between furring strips, finished with gypsum wall board or panelling. The insulation may be fibrous batt, rigid board, or fibrous blown-in insulation. DESIGN FEATURES Interior Finishes Split faced, scored, burnished, and fluted block give

owners and designers added options to standard block surfaces. Colored units can be used in the entire wall or in sections to achieve specific patterns. Although construction with staggered vertical mortar joints (running bond) is standard for basement construction, the appearance of continuous vertical mortar joints (stacked bond pattern) can be achieved by using of scored units or reinforced masonry construction. Natural Lighting Because of the modular nature of concrete masonry, windows and window wells of a variety of shapes and sizes can be easily accommodated, giving basements warm, natural lighting. For additional protection and privacy, glass blocks can be incorporated in lieu of traditional glass windows.

REFERENCES 1. Basement Manual-Design and Construction Using Concrete Masonry, TR-68A, National Concrete Masonry Association, 2001. 2. BOCA National Building Code. Country Club Hills, IL: Building Officials and Code Administrators International, Inc. (BOCA), 1999. 3. Building Code Requirements for Masonry Structures, ACI 530-02/ASCE 5-02/TMS 402-02. Reported by the Masonry Standards Joint Committee, 2002. 4. International Residential Code. Falls Church, VA: International Code Council, 2000. 5. International Building Code. Falls Church, VA: International Code Council, 2000. 6. Preventing Water Penetration in Below-Grade Concrete Masonry Walls, TEK 19-3A. National Concrete Masonry Association, 2001. 7. Seismic Design Provisions for Masonry Structures, TEK 14-18, National Concrete Masonry Association, 1996. 8. Specifications for Masonry Structures, ACI 530.1-02/ASCE 6-99/TMS 602-02. Reported by the Masonry Standards Joint Committee, 2002. 9. Standard Building Code. Birmingham, AL: Southern Building Code Congress International, Inc. (SBCCI), 1999. 10.Standard Specification for Grout for Masonry, ASTM C 476-01. American Society for Testing and Materials, 2001. 11.Standard Specification for Load-Bearing Concrete Masonry Units, ASTM C 90-01. American Society for Testing and Materials, 2001. 12.Standard Specification for Mortar for Unit Masonry, ASTM C 270-00. American Society for Testing and Materials, 2000. 13.Uniform Building Code. Whittier, CA: International Conference of Building Officials (ICBO), 1997.

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NCMA TEK

Provided by: Nitterhouse Masonry Products, LLC National Concrete Masonry Association an information series from the national authority on concrete masonry technology

CONSTRUCTION OF HIGH-RISE CONCRETE MASONRY BUILDINGS


(1998)

Keywords: construction techniques, economical construction, high-rise, inspection, load-bearing masonry, scaffolding, specified compressive strength of masonry (f'm)

INTRODUCTION Masonry structures have been used for centuries throughout the world. Concrete masonry units, however, are a relatively recent innovation. Initially, these units were made with hand-operated equipment, although by the 1940’s, block production had developed to incorporate automated mixing, molding, and curing methods, resulting in consistent quality of materials. These new manufacturing processes allowed concrete masonry to be used in engineered structural systems such as multistory load-bearing structures. In the late 1940’s, one of the first examples of engineered multistory construction was used by Professor Paul Haller in Switzerland. Today there are many examples of loadbearing masonry buildings up to 15 to 28 stories high. The modular nature of concrete masonry units makes construction straightforward and the small unit size makes changes in plan or elevation easy. Special unit shapes are manufactured to accommodate reinforcement. Open end units, with one or both end webs removed, permit the place-

ment of units around vertical reinforcing bars. Slots manufactured into the webs of units (termed bond beam units) are used to position horizontal reinforcement within the wall. Concrete masonry is widely used because of the strength, durability, economy, architectural appeal, and versatility of the masonry system. A major milestone in the advancement of engineered concrete masonry was the establishment of the Specifications for Design and Construction of Load Bearing Concrete Masonry by NCMA in the late 1960's (ref. 1). This served as the building code for engineered concrete masonry structures and was adopted by the Southern Building Code Congress and other model codes. It has evolved into our present-day Building Code Requirements for Masonry Structures (ref. 2) and Specification for Masonry Structures (ref. 3). One of the earliest wall bearing concrete masonry structures using this new technology was a nine story senior citizens building in Cleveland, Tennessee which was built in 1969 utilizing partially reinforced concrete masonry walls.

Excalibur Hotel and Casino

(photo)

Figure 1–The four towers of the 28-story Excalibur Hotel in Las Vegas are load-bearing masonry. 102 TEK 3-12 © 1998 National Concrete Masonry Association

In our world of economics, the bottom line is still a deciding factor in determining a building's construction type. The real economy of concrete masonry lies in utilizing the strength of the masonry units (making them load-bearing) and minimizing the cutting of the modular building unit by utilizing multiples of 8 in. for building dimensions and openings. Regarding finish, the most economical one of course is normally plain, painted block. However, if the owner's budget permits enhancements, a wide variety of architectural units are available (i.e. colored, split-face, scored, fluted, burnished, and slump block). Prefaced units with a glazed finish, vibrant colors and graffiti resistance are also available. Architectural units not only provide pleasing aesthetics but also greatly reduce maintenance and upkeep costs. Additionally, stucco or a variety of proprietary finishing systems also can be applied. BUILDING TYPES Most concrete masonry multistory buildings fall into two main types; loadbearing shear wall-type buildings and infilled walls. The Uniform Building Code (ref. 4) has also recently approved a design method for moment-resisting masonry wall frames. Loadbearing/Shear Wall Buildings Loadbearing concrete masonry shear wall buildings make the most effective use of concrete masonry by relying on both the economy and the structural capacity—compressive strength and shear resistance—of the concrete masonry. The most common application uses concrete masonry walls with concrete floor and roof diaphragms. The concrete diaphragms can be poured in place, although precast hollow core slabs are the most common. Concrete masonry/precast slab buildings provide a fast, economical construction method that has allowed some builders to construct one story each week. Floors are enclosed quickly, so that mechanical, electrical, plumbing, and other contractors can begin working on one floor while masonry wall and plank construction continues on floors above them. Concrete Masonry Infill Infilled concrete masonry walls utilize the concrete masonry as cladding and interior partitions between concrete or steel frames, which form the structural load-resisting system. Concrete masonry walls are often used in this application because of the cost effectiveness and ease of construction. Historically, most of these walls have been constructed using standard concrete masonry units which were painted or plastered. More recently, however, architectural units are being used to eliminate the need for finishing the walls. Construction of infilled masonry walls is usually straightforward since the main building system is in place prior to the masonry construction. The most important consideration is whether “gapped” or “ungapped” infilled walls will be provided. Gapped infilled walls are constructed with a predetermined space between the masonry and the building frame. These gaps act as isolation joints, allowing the building frame to drift and sway under lateral loads. Ungapped infilled walls,

by contrast, are constructed tightly against the building frame so that the infilled walls serve as shear walls. DESIGN CONSIDERATIONS The typical specified compressive strength of concrete masonry, f'm, is 1500 psi (10.3 MPa). However, using high strength concrete masonry units, f'm values up to 4000 psi (27.6 MPa) are achievable. These high strength units are often specified on high-rise loadbearing projects to minimize wall thickness. For further economy, some designers specify lower f'm values in the upper stories, where the higher compressive strength is not needed, since high strength units may cost more than standard units. For example, the four, fast-track, 28-story towers of the $300 million, 4,000 room Excalibur hotel in Las Vegas, Nevada, used an f'm of 4000 psi (27.6 MPa) for the loadbearing walls on the first thirteen floors (ref. 5). The specified compressive strength decreased in successive stories, until the top floors where standard block with an f'm of 1500 psi (10.3 MPa) was used. Contractors prefer repetitive floor plans for high-rise construction. This important design feature allows similar construction and provides structural continuity from floor to floor both of which lend to economy in construction. The same holds true for architectural details. Designs which facilitate scheduling repetitive, “assembly-line” construction procedures improve productivity and reduce construction costs. Obviously, aesthetic and functional constraints must also be considered, so that buildings are useful and attractive as well as economical. Connections between building elements is key to the performance of the structures and should therefore be considered carefully during the design process. Connections should be simple and easy to construct and, where necessary, should accommodate building movements from expansion and/or contraction of building materials. Differential movement deserves particular attention on high-rises where concrete masonry is clad with clay brick. Concrete materials tend to shrink, while clay tends to expand. Over the height of many stories, these opposing movements can be significant. In one case, the seventeen story Crittenden Court in Cleveland, Ohio, these movements were accommodated by designing the exterior brick as a reinforced curtain wall supported on the foundation (ref. 6). The brick was tied to the precast concrete floor planks using slotted anchors that allow vertical but not horizontal movement. This accommodates the differential movement, and also provides enough lateral stiffness to transfer wind and seismic loads from the brick to the floor diaphragms. Because of the large size of most multistory buildings, a predefined quality control/quality assurance plan is recommended. Inspection, to ensure that key building elements have been installed properly, is essential to assure that the building was constructed as designed. Material testing may be required by the Specifications for Masonry Structures or the contract documents to verify that supplied materials meet the project specifications. As with all construction, tolerances should be carefully monitored. Steel or concrete frames con103

structed out of tolerance make the mason's job difficult and slow. Proper alignment of these elements will facilitate the construction process and provide a more appealing completed structure. CONSTRUCTION Construction Materials For construction to proceed smoothly and quickly, it is necessary to carefully schedule construction procedures and supply of materials. Where space allows, it is preferable to stockpile materials on site so that they are readily available when needed. For small sites, material delivery must be timed so that the materials can be moved quickly to the place they are needed. Materials are delivered to the masons on upper stories via crane or hoist. Materials can either be stocked from the building floors, or can be placed on the work platform, if the platform is large enough and can support the weight. Coordination with crane and elevator schedules should also be considered so that they are available when materials arrive on site. An adequate supply of concrete masonry units for the entire story should be supplied at one time. Mortar materials can be mixed using traditional techniques, although silo mix mortar systems have become increasingly popular. These systems deliver 14 to 28 yd3 (10.7 to 21.4 m3) of mortar ingredients, and produce consistent mortar from batch to batch. Additional advantages include ability to be lifted easily from floor to floor, mortar containment, and easy cleanup. Reinforcement cut to proper length and provided in bundles for each story level also facilitates construction. Grout is typically supplied via ready-mix trucks and is pumped to the top of the wall or is lifted using cubic yard buckets. Silo mixed grout is also supplied on some jobs. Also, as with all grouted masonry, it is vitally important that the grout has a slump between 8 and 11 in. per the Specification for Masonry Structures for proper placement and final performance of the building. Placing the Masonry Concrete masonry can either be laid from the inside of the building with the masons working on the interior floor area or from the outside of the building with the masons working on scaffolds or work platforms. The choice depends on the size of the job, type of construction, and mason's preferences. Laying Units from Inside the Building For load-bearing and infilled exterior walls, concrete masonry can often be laid from the inside of the building. This normally is the most efficient and cost effective method as this allows the masons to work on the building's floor area providing ample room for units, mortar, and other building materials. Since the mason's work is confined to the perimeter of the floor, other trades can also work at the same time. Laying from the interior may also be an advantage in windy conditions, when work on exterior platforms may be limited. Block for the next story are normally stacked on the concrete floor as soon as it has hardened enough to prevent

damaging the surface, usually a couple of hours after the steel troweling is completed. An example of this is a hotel structure where the wall between each room is a bearing wall and the floor system is a concrete, one-way, continuous slab. To ensure structural adequacy and maximum economy, two practices must be observed: 1) no shoring can be removed until the next story of walls has been laid up, and 2) sand must be spread over the new slab to facilitate cleanup of any dropped mortar. For masonry veneers laid from the interior, the building design and construction must accommodate the construction technique. For example, if the walls are masonry veneer with concrete masonry backup, both masonry wythes can easily be laid at the same time. If, on the other hand, the interior wythe is steel studs with sheathing, the veneer would have to be placed from the exterior. Similarly, large columns and deep beams may interfere with masonry veneer placement from the interior. One drawback to laying units from the inside of the building is that more time is typically required to place the units to assure they align on the exterior since the masons are facing the interior, unexposed, side of the wall. However, this decrease in productivity is often offset by large reductions in scaffolding costs, which can be substantial. Although some scaffolding is needed to lay the top portion of each wall, only one level of scaffold is required. Laying Units from Work Platforms Scaffolds and other temporary work platforms allow the masons to work facing the exposed side of the masonry, making it easier to ensure the exposed side is laid plumb and level. Most mason contractors own a supply of scaffolding, but often must rent supplemental scaffolds for high-rise construction. Time should be allotted for placing, dismantling, and moving scaffolds on the job. Two alternatives to traditional scaffolding for high-rise construction are powered mast-climbing platforms and suspended scaffolds. Both eliminate the labor required to construct multiple levels of conventional scaffolding. Powered mast-climbing work platforms are erected on the ground and use electric or hydraulic power to move the platform up and down the supporting mast or masts (ref. 7). The masts are attached to the building using adjustable ties or anchors. One advantage of these systems is that the platform can be easily moved in small increments. This means the platform can be adjusted as the wall is laid to keep it at the mason's optimum working height. This reduces the amount of lifting of individual units and improves productivity. Powered mastclimbing platforms have maximum heights ranging from 300 to almost 700 ft (91 to 213 m), depending on the type chosen. Other variables include maximum safe wind exposure, attachment requirements, speed, and optional equipment such as overhead protection. Suspended scaffolds (ref. 8) are work platforms that are suspended from either the roof of the building or from an intermediate floor and therefore would mainly be limited to use on infill projects where the structural frame precedes the wall. Like the mast-climbing platforms, the suspended scaffolds are 104

adjustable in small increments to keep the platform at the optimum working height for the masons. Most suspended scaffolds are raised and lowered by hand, rather than by a powered system. The attachment requirements for suspended scaffolds are fairly complex, and are typically designed for each project and installed by the scaffold supplier. Suspended scaffolds have the advantage of keeping the lower floors of the building accessible once the work has progressed above this point. They may also be preferable on sloping sites where erection of frame scaffolding would be difficult. Suspended scaffolds typically become cost effective at building heights of seven to ten stories. Below this height, traditional or power mast scaffolding is probably more cost effective.

CONCLUSION Many economical concrete masonry structures have been built around the country ranging from buildings to over twenty stories in height to fifteen foot high retaining walls. Rapid growth in areas like that of Orlando, Florida, spurred by the arrival of Disney World produced a market for quality, economical building systems. Concrete masonry construction and the early NCMA Specification for Design and Construction of Load-Bearing Concrete Masonry were ready with the technology to allow engineers and architects to design economical and aesthetically pleasing structures. High-rise buildings have seen an unprecedented growth with modern, innovative construction methods, proper engineering design and use of concrete masonry materials.

REFERENCES 1. Specification for Design and Construction of Load-Bearing Concrete Masonry, National Concrete Masonry Association, 1970. 2. Building Code Requirements for Masonry Structures, ACI 530-95/ASCE 5-95/TMS 402-95. Reported by the Masonry Standards Joint Committee, 1995. 3. Specification for Masonry Structures, ACI 530.1-95/ASCE 6-95/ TMS 602-95. Reported by the Masonry Standards Joint Committee, 1995. 4. Uniform Building Code. Whittier, CA: International Conference of Building Officials (ICBO), 1997. 5. Keating, Elizabeth. "A Floor a Week per Tower." Masonry Construction, November 1989. 6. Keating, Elizabeth. "Powered Mast-Climbing Work Platforms." Masonry Construction, May 1997. 7. Wallace, Mark A. "Loadbearing Masonry Rises High in Cleveland." Masonry Construction, May 1997. 8. Hooker, Kenneth A. "Suspended Scaffolds Cut High-Rise Masonry Costs." Masonry Construction, March 1991.

Provided by: Nitterhouse Masonry Products, LLC Disclaimer: NCMA and the companies disseminating this technical information disclaim any and all responsibility and liability for the accuracy and the application of the information contained in this publication.



NCMA TEK

Provided by: Quik-Brik National Concrete Masonry Association an information series from the national authority on concrete masonry technology

CONSTRUCTION OF LOW-RISE CONCRETE MASONRY BUILDINGS

TEK 3-13 Construction (2005)

Keywords: architectural details, bond beams, composite wall, construction details, construction techniques, flashing, joint reinforcement, construction techniques, lintels, water repellents, weep holes. INTRODUCTION The current trend of urban renewal and infill has sparked a high volume of new low-rise masonry residences. These structures come in many forms, but quite often they employ the use of load bearing concrete masonry walls supporting a wood floor system. These new buildings are largely derivative of the historic loadbearing masonry “brownstone” or “three flat” structures of old. This guide is intended to assist contractors and architects to give this building type a modern approach to detailing. FLOOR SYSTEM CONNECTIONS When designing low-rise loadbearing structures, the connection detail between the floor system and the wall system is critical for achieving a watertight structure. Much of this TEK will deal with which strategy should be utilized in connecting a wood floor system to a masonry load-bearing wall. Connection methods covered are joist hangers, beam pockets and ledger beam details. Other floor systems are used in low-rise construction that are not addressed here see TEK 5-7A for further information (ref. 2). BRICK AND BLOCK COMPOSITE WALL DETAILS Quite often, the front facade of these structures is composed of brick to give the building a more residential, more human scale. One way to construct a brick and block wall is to separate the two wythes with an airspace, creating a cavity wall. Another is to use a composite wall design. The composite wall consists of an exterior wythe of brick directly mortared or grouted and tied to an inner wythe of CMU. The collar joint between the two wythes should be 100% solid as it is the only defense against water penetration. Minimum tie requirements are one tie per 22/3ft2 of wall area for W1.7 (MW11)(9 gauge) wire or one tie per 41/2ft2 of wall area using W2.8 (MW19)(3/16 in.)wire (ref. 2). A W1.7 (MW11)(9 gauge) joint reinforcement @16 in. (406 mm) on center would meet this requirement and is often used. Details covered for this system are base flashing, window head and window sill details. EXTERIOR CONCRETE MASONRY The use of water repellent admixtures in concrete masonry and mortars can greatly reduce the amount of water entering the masonry. In addition, they inhibit any water that penetrates the face from wicking to the back of the wall.

Figure 1––Exterior Concrete Masonry in a Residence Proper selection and application of integral water repellents and surface treatments can greatly enhance the water resistive properties of masonry, but they should not be considered as substitutes for good fundamental design including flashing details and crack control measures. See TEKs 19-1, 19-2A and 19-4A (refs. 6, 3, & 5) for more information on water resistant concrete masonry construction. Because a 4 in. (102 mm) concrete masonry veneer will shrink over time, a 4 in. (102 mm) hot-dipped galvanized ladder type joint reinforcement should be placed in bed joints spaced 16 in. (406 mm) vertically. Compared to type N or O, type S mortar tends to be less workable in the field and should only be specified when dictated by structural requirements. Sills, copings and chimney caps of solid masonry units, reinforced concrete, stone, or corrosion resistant metal should be used. Copings, sills and chimney caps should project beyond the face of the wall at least 1 in. (25 mm) and should have functional flashing and weep holes. In addition, all sills, copings and chimney caps should have a minimum slope of 1:4, be mechanically anchored to the wall, and should have properly sized, sealed, and located movement joints when necessary. Flashing should be installed at locations shown on the plans and in strict accordance with the details and industry standard flashing procedures. Functional, unpunctured flashing and weep holes are to be used at the base of wall above grade, above openings, at shelf angles, lintels, wall-roofing intersections, chimneys, bay windows, and below sills and copings. The flashing should be extended past the face of the wall. The flashing should have end dams at discontinuous ends, and properly sealed splices at laps. 106


JOIST HANGER DETAILS

BEAM POCKET DETAILS

The use of a joist hanger system can greatly simplify the bearing detail. The floor system does not interrupt the continuity of the bearing wall. Installation is quicker and easier resulting in a more economical installation.

The traditional beam pocket detail still can be effective. Stepped flashing above the bearing line is critical to the performance of this system. Without the flashing, any water present in the wall has an unobstructed path inside the building and has the potential to deteriorate the floor structure.

Block & mortar treated with integral water repellent (where required) Stepped Through wall flashing

Block & mortar treated with integral water repellent (where required)

2 wythes of 4 in. (102 mm) CMU Inner wythe cut to form pocket

Through Wall Flashing

Drip Edge

Drip Edge Joist Hanger

Grouted Bond Beam

Grouted Bond Beam

Figure 2––Joist Hanger Bearing Detail

Figure 4––Beam Pocket Bearing Detail

2 Wythes of 4 in. (102 mm) CMU

Stepped through wall flashing

Stepped Through Wall Flashing

Strap anchor in head joint.

Strap Anchor

2 wythes of 4” (102 mm) CMU

Drip Edge

Drip Edge Grouted Bond Beam

Figure 3

Joist Hanger Non-Bearing Detail

Grouted Bond Beam

Figure 5

Beam Pocket Non-Bearing Detail

107

LEDGER BEAM DETAILS

PARAPETS AND WINDOW SILLS

The use of a ledger beam which is bolted to a bond beam is also a good option for this bearing condition. Through wall flashing is still required to maintain a watertight wall. Any water that penetrates the block with run down the inner cores of the block until it hits the flashing. The flashing and weep holes will allow the water to exit without damaging the structure.

Below are details for a parapet condition and a window sill condition. The parapet is reinforced with No. 4 bars at 48 in. (No.13M @1219 mm) on center or as required for wind resistance. If a metal cap is used, it should extend down the face of the wall at least 3 in. (76 mm) with continuous sealant at the joint on both sides of the wall. The sill detail shows the arrangement of flashing, end dam, weep holes and drip edge and how they all form a watertight

Optional: Counterflashing or waterproofing adhered to CMU Block & mortar treated with integral water repellent (where required) Through wall flashing

Block & mortar treated with integral water repellent (where required) Metal coping

Drip edge

Continuous sealant (both sides)

Anchor bolts grouted into bond beam

Flashing

Ledger Beam

Bond Beam Reinforcement if required for wind resistance.

Grouted Bond Beam

Figure 6––Ledger Beam Bearing Detail

Figure 8––Parapet Detail

Joint reinforcement as required

Flashing Flashing end dam Through wall flashing

Cotton sash weep

Drip edge

Grouted cell (under flashing)

Anchor bolts grouted into bond beam

Drip edge

Ledger Beam

Grouted Bond Beam

Figure 7––Ledger Beam Non-Bearing Detail

Figure 9––Window Sill Detail

108

WINDOW HEAD DETAILS

CONTROL JOINT DETAILS

These two window head details show the relationship between the steel lintel, drip edge, flashing, end dams, and weep holes. The first option shows the use of a concrete masonry lintel which is grouted solid and reinforced. The second detail shows two steel lintels used for spanning the opening.

Control joints simply are weakened planes placed at approximately 20 ft. (6 m) on center in concrete masonry walls and at changes in wall elevation/thickness. Notice that the joint reinforcement is discontinuous at the joint. Cores are shown grouted adjacent to the joints as well to ensure structural stability in taller walls and/or high load situations.

Joint Reinforcing Rebar / Grout Mortar Backer Rod Sealant

Joint reinforcing as required Flashing

Joint Reinforcing

Cotton weep

Rebar / Grout

Drip edge

Mortar

Bond beam

Backer Rod Sealant

Figure 10––Masonry Lintel Detail

Figure 12––Control Joint Details

Control joint location using masonry lintel Control joint location when using steel lintel

Flashing with end dams Joint reinforcing as required Control joint Steel lintels Cotton weep Drip edge

Figure 11––Double Angle Lintel Detail

Additional control joint [if opening is more than 6 ft. (1.8 m)wide]

Figure 13––Control Joint at Opening

109

COMPOSITE WALL BASE FLASHING DETAILS

COMPOSITE WALL WINDOW DETAILS

Figure 14 shows a stair-stepped flashing detail with the exposed drip edge and weep holes. Figure 15 shows a straight through wall flashing detail. The flashing must be set in mastic on top of the concrete foundation, or the flashing must be self adhesive. The flashing should be turned up on the inner side of the wall to direct water to the outside of the wall.

Here steel lintels back-to-back create the above window span. Stepped flashing turned up on the inside, and folded to form an end dam protects the head condition from moisture. The sill detail also uses flashing, end dams and weep holes to keep moisture out of the wall. The use of a precast concrete or stone sill is highly suggested over using brick rowlock sills.

Flashing support angle Stepped through wall flashing Continuous collar joint Cotton sash weep @16 in. (406 mm) o.c. Drip Edge

Continuous collar joint

Flashing End Dam Cotton sash weep Stepped flashing Drip Edge Steel Lintel

Figure 14––Stepped Flashing at Base

Figure 16––Window Head Detail

Joint reinforcement as required Collar joint Sealant and backer rod Flashing end dam Continuous collar joint Flashing support angle Through wall flashing

Cotton sash weep

Flashing Drip Edge Grouted solid

Cotton weep 16 in. (406 mm) o.c. Drip Edge

Figure 15––Level Flashing and Angle

Figure 17––Window Sill Detail

110

* All joint reinforcement should be hot-dipped galvanized (minimum)

8 in. (203 mm) CMU 1 in. (25 mm) Rigid insulation

SECTION

Figure 18 shows the detailing of a 4 in. (102 mm) concrete masonry veneer used in conjunction with a 8 in. (205 mm) CMU backup wall. Three types of joint reinforcement are shown including tri-rod, tab and adjustable types. It is imperative that the veneer have a continuous wire embedded in every other course to control movement. With the tri-rod system, the joint reinforcement satisfies this requirement. With the other two systems, an additional ladder type joint reinforcement is used to provide this movement control for the veneer.

PLAN

CONCRETE MASONRY VENEER DETAILING

Tri-rod joint reinforcement @ 16in. (406 mm) o.c. vertically*

Tab type reinforcement@ 16 in. (406 mm) o.c. vertically*

1 in. (25 mm) airspace

Adjustable joint reinforcement@ 16 in. (406 mm) o.c. 4 in. (102 mm) 2 wire ladder joint reinforcement @ alternate 16 in. (406 mm) o.c.

4 in. (102 mm) 2 wire ladder joint reinforcement@ alternate16 in. (406 mm) o.c. vertically

4 in. (102 mm) CMU Flashing

Tri-rod

Tab type

Adjustable

Figure 18––Concrete Masonry Veneer Detailing

REFERENCES 1. 2. 3. 4. 5. 6.

Building Code Requirements for Masonry Structures, ACI 530-05/ASCE 6-05/TMS-402-05. Reported by the Masonry Standards Joint Committee, 2005. Floor and Roof Connections to Concrete Masonry Walls, NCMA TEK 5-7A. National Concrete Masonry Association, 2001. Design for Dry Single-Wythe Concrete Masonry Walls, NCMA TEK 19-2A. National Concrete Masonry Association, 2004. Flashing Details for Concrete Masonry Walls, NCMA TEK 19-5A. National Concrete Masonry Association, 2004. Flashing Strategies for Concrete Masonry Walls, NCMA TEK 19-4A. National Concrete Masonry Association, 2003. Water Repellents for Concrete Masonry Walls, NCMA TEK 19-1. National Concrete Masonry Association, 2002.

Provided by: Quik-Brik Disclaimer: Although care has been taken to ensure the enclosed information is as accurate and complete as possible, NCMA does not assume any responsibility for errors or ommisions resulting from the use of this TEK

NATIONAL CONCRETE MASONRY ASSOCIATION 13750 Sunrise Valley Drive, Herndon, Virginia 20171-4662 www.ncma.org

To order a complete TEK Manual or TEK111 Index, contact NCMA Publications (703) 713-1900


POST-TENSIONED CONCRETE MASONRY WALL CONSTRUCTION Keywords: construction techniques, post-tensioned masonry, prestressed masonry, quality assurance, prestressing tendons, tensioning INTRODUCTION Prestressing is the general term used when a structural element is compressed prior to being subjected to building loads. This initial state of compression offsets tensile stresses from applied loads. Post-tensioning is a specific method of prestressing where tendons are stressed after the wall has been placed. The other type of prestressing, called pretensioning, involves tensioning the tendon prior to construction of the masonry. Because virtually all prestressed masonry built to date has been post-tensioned, the two terms are often used interchangeably as they apply to this form of masonry design and construction. Post-tensioned concrete masonry walls have been built for schools, retail, manufacturing, highway sound barriers, warehouses and other types of structures. In addition, post-tensioning has been used to strengthen and repair existing masonry walls. This TEK addresses new concrete masonry walls laid in running bond and built with unbonded vertical post-tensioning tendons. Post-Tensioned Concrete Masonry Wall Design, TEK 14-20A (ref. 1) addresses the structural design of vertically post-tensioned walls. POST-TENSIONING In post-tensioned construction, hollow concrete masonry units are laid conventionally and prestressing tendons are either placed in the concrete masonry cells or in the cavity between multiple wythes. Current design codes (ref. 3) typically address post-tensioning of masonry walls laid in running bond. The cells or cavity containing the tendons may or may not be grouted. Grouting helps increase cross-sectional area for shear and compressive resistance, but increases construction cost and time. Prestressing tendons are either installed during wall construction, or access ports are left in the walls so the tendons can be slipped in after the walls are completed. In either case, the tendons are tensioned only after the walls have cured for approximately three to seven days.


MATERIALS Construction of a post-tensioned wall proceeds similarly to that of conventional masonry. The materials are the same, with the addition of hardware to develop the posttensioning forces, steel prestressing tendons which can be wires, bars or strands, and sometimes prestressing grout. Concrete Masonry Units Open-ended (A- and H-shaped) concrete masonry units (Figure 1) are particularly suited to post-tensioned masonry , as these units can be placed around the tendons without having to lift the units over the tendons. While these two-core units are commonly used, proprietary units are also being developed that are specifically intended for use with tendons. The net area strength of concrete masonry units must be at least 1,900 psi (13.1 MPa) per Standard Specification for Loadbearing Concrete Masonry Units (ref. 2). However, stronger units are often specified for post-tensioned walls to utilize the higher compressive strength. Mortar and Grout Type S mortar is commonly used for conventional loadbearing masonry, and Type S is a good choice for posttensioned masonry as well. Higher early strength mortars can accommodate earlier stressing. Because mortar must be placed on concrete masonry webs adjacent to grouted cores to contain the fluid grout, full mortar bedding is sometimes specified when grout is used. Mortar bedding is a design issue as well, as the section properties of a wall with face shell mortar bedding are different from those of a fully bedded wall. Because this TEK addresses unbonded tendons only, the

Figure 1—Open -Ended Concrete Masonry Units 112


(2002)

grout discussed here is conventional grout (ASTM C 476, ref. 6), not prestressing grout. Prestressing grout is only used with bonded tendons. Encasing tendons in conventional grout restrains the tendons, but they are still considered unbonded. Tendons In the United States, tendons are usually high-strength bars joined by couplers, although Building Code Requirements for Masonry Structures (ref. 3) also allows steel strands or wires to be used. Couplers allow the use of shorter bars which minimizes the height of lifting. To date, there are no code provisions for tendons which are not steel. Important features of the tendons are their size, strength, and relaxation characteristics. Most tendons currently available in the United States are bars between 7/16 and 1 in. (11 and 25 mm) in diameter, with strengths between 60,000 and 100,000 psi (413 and 690 MPa), depending on the supplier. Steel strand tendons are generally 270,000 psi (1,860 MPa). Tendons are usually placed in hollow cells of masonry units with little or no grouting, except for certain shear walls (these must be identified on the design drawings). In addition, the open-ended units shown in Figure 1 must be grouted to meet minimum web requirements in ASTM C 90 (ref. 2). Tendon Corrosion Protection Tendons must be protected from moisture deterioration, and the design documents should indicate the type of protection required. Tendons in walls with a likelihood of high moisture levels (single wythe exterior walls in areas of high humidity and interior walls around swimming pools, locker rooms, etc.) must have corrosion protection in addition to that provided by the masonry cover, such as hot-dipped galvanizing (ref. 3). In practice, most prestressing tendons are supplied with a hotdipped galvanized coating. It is considered good practice to use additional corrosion protection, such as flexible epoxy-type coatings, for tendons in moist environments. Grouting While the need for grouting is minimized compared to conventionally reinforced walls, grout is still needed for mild reinforcement, anchorages for the tendons, such as in bond beams, and tendon restraints.

Concrete masonry unit Foundation or support

Tendon

Continuous bond beam (inverted) Foundation or support

Cast-in-place anchor

2a—Cast-in-place anchor

Anchorages Each tendon is anchored at the foundation and extends to the top of the wall. Building Code Requirements for Masonry Structures (ref. 3) requires that tendons be anchored by mechanical embedments or bearing devices or by bond development in concrete. Tendons can not be anchored by bond development into the masonry. The foundation anchorage is embedded in the wall or footing while the top anchorage utilizes a special block, a precast concrete spreader beam or a grouted bond beam. Unless the design documents call out specific bottom anchors, the contractor must select the anchor appropriate to the conditions. The cast-in-place bottom anchor (Figure 2a) is preferred for shear walls and for fire walls. While they are the best anchors for capacity, cast-in-place anchors are the most difficult to align. Cast-in-place anchors are often set by the foundation contractor, not the mason. Thus, quality control is a concern with these anchors. The mason controls bottom anchor placement when either adhesive anchors are installed in the foundation (Figure 2c), or when an anchor is used which does not rely on the foundation for support (Figure 2b). If the anchor in Figure 2b is used, foundation dowels are grouted into the wall to lock it in place. In some instances, tendons can also begin at an upper floor and not at the foundation. In this case, the foundationless anchor is used with a bond beam, similar to Figure 2b. The mechanical post-installed anchors can be used for nearly all applications, while the adhesive type should not be used for fire walls. CONSTRUCTION Key steps of post-tensioning concrete masonry walls include: selecting and setting the bottom anchorages; installing the tendons; selecting and setting the top anchorages; and tensioning the tendons. Bottom Anchors Bottom anchors are most critical to the proper construction of post-tensioned walls. Alignment is essential to ensure that the tendons are placed exactly as intended.

Tendon Bond breaker tape (2) No. 4 (M #13) continuous Foundationless threaded floor slab anchor

Concrete masonry unit

Tendon

Foundation or support

Dowel into slab or wall (locate minimum 8 in. (203 mm) from tendon)

2b—Foundationless anchor

Adhesive anchor

2c—Adhesive anchor

Figure 2—Bottom Anchors for Use in Post-Tensioned Masonry 113

Tendons Tendons are usually placed concentric with the wall. However, they may be placed off-center to counteract bending moments due to eccentric vertical forces or lateral forces from a single direction. However, tendons should not be placed such that tensile stresses develop in the wall due to the combination of prestressing force and dead load. Laterally-unrestrained tendons are free to move within the cell or cavity and are the simplest to construct. Laterally restrained tendons are not free to move within a cell or cavity. Restraint is accomplished by grouting the full height of the tendon or by providing intermittent restraints—either grout plugs or mechanical restraints—at the quarter points of the wall height. Placing tendons is much like that of mild reinforcement. They may be installed after the masonry is constructed provided the design allows laterally-unrestrained tendons. If laterally-restrained tendons are required, the tendon placement should proceed simultaneously with the masonry to allow the restraints to be installed unless the cells will be grouted. Tendon positioners (see Figure 3) are useful to maintain the tendon location within the wall during construction of the masonry. Positioners may also function as restraints if their capacity is determined by testing. In all details, the tendons must be able to slip freely. If grout encases the tendon either totally or at restraints or bond beams, a bond breaker such as poly tape should be used to allow the tendon to slip. Tendons can also be either bonded or unbonded. Bonded tendons are encapsulated by prestressing grout in a corrugated duct which is bonded to the surrounding masonry by grout. Both the prestressing grout inside the duct and the grout around the duct must be cured before the tendons are stressed. Thus, bonded tendons are also laterally-restrained. All other tendons are unbonded. However, unbonded tendons may be either laterally-restrained or unrestrained. Walls with laterally-unrestrained and unbonded tendons do not require grouting

Grouted cell Mesh grout stop

QUALITY ASSURANCE

Locate couplers to avoid lateral restraints

Bond breaker tape Tendon

Positioner t

/2

Top Anchors The top anchor must be placed on solid masonry, a grouted bond beam or a precast concrete unit. The anchor should not be supported by mortar. Figure 4 shows a means for supporting the top of a wall when the top anchor is placed on a bond beam in a lower course. This detail can also be used for interior partitions. Tensioning At the time the tendons are stressed, the masonry is considered to have its initial strength (f 'mi). The project specification should include either the minimum f 'mi and minimum specified compressive strength of masonry ( f 'm), or the amount of curing required before stressing can occur. The sequence of tensioning, whether it is accomplished by fully stressing each tendon sequentially or by stressing the tendons in stages, is a function of the design specifications. Prestressed masonry design, and therefore the structural integrity of these walls, relies on an accurate measure of the prestress in the tendons. To ensure the required level of accuracy, Specification for Masonry Structures (ref. 4) requires that the following two methods be used to evaluate the tendon prestressing force: 1. measure the tendon elongation and compare it with required elongation based on average load-elongation curves for the prestressing tendons, and either: 2a. use a calibrated dynamometer to measure the jacking force on a calibrated gage, or 2b.for prestressing tendons using bars of less than 150 ksi (1,034 MPa) tensile strength, use load-indicating washers complying with Standard Specification for Compressible-Washer-Type Direct Tension Indicators for Use with Structural Fasteners, ASTM F 959 (ref. 5). If the two values determined by methods 1 and 2 are not within 7 percent of each other, the cause of the difference must be corrected.

t

Remove and replace face shell for access to coupler

and are generally the most economical to construct. However, the wall performance will not be as good as with laterally restrained tendons. The designer must specify which system will be used. For some conditions, primarily seismic, grouted conventional reinforcement is used in addition to post-tensioning tendons to provide minimum requirements of bonded reinforcement. However, post-tensioned walls are most economical when the grouting is minimized or eliminated totally in comparison to a conventionally reinforced wall. The higher cost of the post-tensioning materials is more than offset by the savings of placing fewer tendons compared to reinforcing bars and eliminating most of the grouting.

t

/2

Figure 3—Tendon Coupler and Positioner

Post-tensioned walls must be constructed in conformance with masonry standards applicable to conventionally reinforced masonry. In addition to these, Specification for Masonry Structures (ref. 4) requires the following for posttensioned masonry: 114

1. In the out-of-plane direction, the tolerance for the tendon placement shall be + 1/4 in. (6 mm) for masonry beams, columns, walls, and pilasters with cross-sectional dimensions less than 8 in. (203 mm). For cross-sectional dimensions greater than 8 in. (203 mm), the tolerance increases to + 3/8 in. (10 mm). 2. In the in-plane direction, the tolerance for tendon placement is +1 in. (25 mm). 3. If tolerances exceed these amounts, the Architect/Engi-

Soft joint, fire-rated as required Lateral tendon restraint anchor bolted or welded to bottom flange of beam to provide simple support at top of wall Veneer Continuous bond beam Extend tendon such that it is properly engaged with projected tabs of restraint anchor

neer should evaluate the effect on the structure. REFERENCES: 1. Post-Tensioned Concrete Masonry Wall Design, TEK 14-20A. National Concrete Masonry Association, 2002. 2. Standard Specification for Loadbearing Concrete Masonry Units, ASTM C 90-01a. ASTM International, 2001. 3. Building Code Requirements for Masonry Structures, ACI 530-02/ASCE 5-02/TMS 402-02. Reported by the Masonry Standards Joint Committee, 2002. 4. Specification for Masonry Structures, ACI 530.1-02/ASCE 6-02/TMS 602-02. Reported by the Masonry Standards Joint Committee, 2002. 5. Standard Specification for Compressible-Washer-Type Direct TenSteel structure sion Indicators for Use with StrucRemove and replace tural Fasteners, ASTM F 959-01a. face shell for access ASTM International, 2001. to bearing plate 6. Standard Specification for Grout Nut, hardened washer for Masonry, ASTM C 476-01. ASTM and load-indicating washer International, 2001. Bearing plate (2) No. 4 (M #13) continuous Grout cell solid Bond breaker tape Mesh grout stop

Figure 4—Top Anchor

Provided by:





PRODUCTIVITY AND MODULAR COORDINATION IN CONCRETE MASONRY CONSTRUCTION


sonry unit weight greatly impacts masonry productivity, with lighter weight units resulting in higher productivity rates (other factors being equal). Based on typical hollow concrete masonry units, the use of lightweight concrete masonry units (less than 105 pcf (1,680 kg/m3) concrete) can increase productivity 10% to 18% over heavyweight units (125 pcf (2,000 kg/m3) or denser concrete) 8-in. (203-mm) units, and 20% to 54% for 12-in. (305-mm) units (refs. 3, 4). Bond pattern can also affect productivity. Because masonry crews are accustomed to laying concrete masonry

Keywords: construction techniques, economics, modular coordination, productivity

INTRODUCTION

For masonry construction, productivity is typically thought of as the number of concrete masonry units placed per unit of time. This production rate is influenced by many factors, some of which can be controlled by the mason and others which are beyond the mason's Figure 1—Estimated Production Rates Based on control. Concrete Masonry Unit Weight (ref. 4) PRODUCTIVITY RATES Ideally, concrete masonry productivity rates should be compiled by masonry estimators, based on records of completed jobs. Published productivity rates, such as those shown in Figure 1 and Table 1, should be used as guidelines only. The following sections discuss some of the various factors that can impact masonry productivity. In addition to these, productivity rates can vary with unit size and concrete density, mortar workability, masonry bond pattern, number and type of wall openings, amount of reinforcement and wall size. As illustrated in Figure 1, concrete ma-

Production, units per mason per day

250 200 150 100 50 0 10

20

30

40

50

60

Weight of unit, lb

Table 1—Typical Concrete Masonry Productivity Ratesa Unit nominal size and description: 4 x 2 x 8 concrete brick units 8 x 8 x 16 standard concrete masonry units 8 x 8 x 16 split face concrete masonry units

Productivity, number of units per mason per dayb 550 to 650 135 to 190 80 to 160

Notes: a Values assume: walls are constructed in running bond with standard 3/8 inch (10 mm) thick mortar joints and are of convenient height; adequate masonry labor is available; and walls incorporate modular layout to minimize cutting. b To obtain square feet of wall per day, multiply the values in the table by 0.89 (multiply by 0.083 to obtain m2/day). 116 TEK 4-1A © 2002 National Concrete Masonry Association

(2002)

primarily in running bond, other bond patterns often require more time to lay. For example, stack bond has been estimated to decrease productivity by about 8% over comparable running bond productivity rates (ref. 4). IMPACT OF QUALITY ON PRODUCTIVITY The overall quality of the project can influence the masonry productivity. Quality construction includes: 1. pre-bid and pre-construction conferences, 2. proper design, 3. attention to planning and layout, 4. quality materials, 5. adequate jobsite and 6 proper installation. A project with these ingredients will also be conducive to a very productive jobsite. Pre-Bid and Pre-Construction Conferences Pre-bid and pre-construction conferences should be held and attended by all parties involved in the masonry work including the owner’s representative, the architect/engineer, the contractor, the construction manager, the masonry material suppliers and the mason contractor. This facilitates good communication prior to the commencement of work and prior to the development of any misunderstandings. Clear communication minimizes delays due to factors such as lastminute changes and errors. Proper Design Quality design means that the designer has: • designed and detailed a project that is constructible, • developed plans and specifications that are sufficient for construction and are complete with the proper code and standards referenced, • reviewed the plans, specifications and structural drawings to eliminate conflicting words and conflicting details, • included the input of a quality mason contractor, and • incorporated all masonry materials into CSI Division 4. (Often, some mason materials are found in division 7. If all of the mason’s work is placed into Division 4, it enhances communication with the masonry team and has a better chance of being properly incorporated into the job.) Similar to the pre-bid and pre-construction conferences, a comprehensive set of plans and specifications will help enhance productivity because it will reduce or eliminate time spent correcting misunderstandings and errors. A complete set of plans and specifications will include a copy of Building Code Requirements for Masonry Structures and Specification for Masonry Structures (refs. 1, 2), the national consensus standards for masonry design and construction. In addition, applicable ASTM standards should be included for specifying masonry materials. Planning and Layout Attention to planning of the building itself and of construction sequencing and scheduling can impact masonry productivity.

Concrete masonry structures can be constructed using virtually any layout dimension. However, for maximum construction efficiency and economy, concrete masonry elements should be designed and constructed with modular coordination in mind. Modular coordination is the practice of laying out and dimensioning structures to standard lengths and heights to accommodate modular sized building materials. Standard concrete masonry modules are typically 8 in. (203 mm) vertically and horizontally, but may also include 4in. (102-mm) modules for some applications. These modules provide the best overall design flexibility and coordination with other building products such as windows and doors. Typically, masonry opening widths for doors and windows should be 4 in. (102 mm) larger than the door or window width. This allows for 2 in. (51 mm) on each side of the opening for framing. Masonry opening heights for windows typically are 8 in. (203 mm) greater than the window height. This opening size allows for 2 in. (51 mm) above and below for framing and 4 in. (102 mm) for installing a sill at the bottom of the window. Masonry opening door heights are 2 in. (51 mm) greater than the door height, which leaves 2 in. (51 mm) for the door framing. Figure 2 illustrates these opening sizes. Thus, door and window widths of 28 in., 36 in., 44 in., and 52 in. (711, 914, 1118 and 1,321 mm), and so on in 8 in. (203 mm) increments, are modular and would not require cutting of the masonry. Modular window heights are any multiple of 8 in. (203 mm), with a masonry window opening 8 in. (203 mm) greater than the height of the window if a 4 in. (102 mm) sill will be used. Similarly, a modular door height is 2 in. (51 mm) less than any multiple of eight. Thus, an 86 in. (2,184 mm) high door, which fits into an 88-in. (2,235 mm) high masonry opening, has a modular height. Note that products are available in some locations to accommodate 6' - 8" (2,032 mm) doors in masonry walls without the need for cutting the masonry units. These include precast lintels with a 2 in. (51 mm) notch which provides the necessary 6' - 10" (2,083 mm) masonry opening to accommodate the door and frame. In other areas, door frames are available with a 4 in. (101.6 mm) header which would allow a 6' - 8" (2,032 mm) door to fit into 7' - 4" or 88 in. (2,235 mm) high masonry opening. Nonmodular layouts may require additional considerations for items such as using nonstandard units or saw cutting masonry units and maintaining bond patterns. Additionally, other construction issues may arise, such as placement of jamb reinforcement and adequate grout consolidation within small core spaces. The end product typically is more difficult to construct, produces more waste and is more costly. Similarly, coordinating the placement of pipes, ducts, chases and conduits to align them with hollow masonry cores can reduce the need to saw-cut masonry units. Steel congestion in reinforced masonry can slow productivity. Placing too many reinforcing bars in too small a space makes it difficult to place the steel and to provide adequate grout coverage. Specification for Masonry Structures (ref. 3) requires 1/4 in. (6.4 mm) clear space between the 117

reinforcing bar and the masonry for fine grout and 1/2 in. (13 mm) clear space for coarse grout. Sample panels reduce misunderstandings and provide an objective indicator of the intended construction practices. They help ensure all parties understand the range of materials, methods and workmanship acceptable on the job. Sample panels are typically at least 4 ft by 4 ft (1.22 x 1.22 m) and should contain the full range of unit and mortar colors. Selecting units of all one shade for the sample panel will not accurately reflect the completed work. Instead, units should be randomly selected as they would in the project construction. Cleaning procedures, sealant application and all other procedures should be performed on the sample panel so that their acceptability can be judged as well. The sample panel should remain in place throughout construction as a point of reference. For maximum productivity, timely delivery of the units, mortar, grout and other masonry materials will help expedite the job. In addition, schedule masonry work to avoid times of the year particularly subject to freezing temperatures or prolonged rains whenever possible. Although masonry construction can take place during hot, cold and wet weather conditions, special construction procedures may be warranted in some cases to ensure the masonry quality is not impacted by the weather. More detailed information on these construction procedures can be found in All-Weather Concrete Masonry Construction (ref. 4). Quality Materials Masonry materials have a successful history of meeting applicable specifications and project requirements. Ensuring that the materials used are as specified helps keep the masonry construction on track. ASTM standards for masonry units, for example, specify dimensional tolerances for the units. Units meeting the ASTM tolerances will be easier to place, and allow the mason to more easily maintain level and alignment. Similarly, units without excessive chippage (a characteristic also governed by ASTM stan-

Masonry opening width = window opening width + 4 in. (102 mm)

2 in. (51 mm) framing

2 in. (51 mm) framing 2 in. (51 mm) framing

Masonry opening height = window opening height + 8 in. (203 mm)

2 in. (51 mm) framing

4 in. (102 mm) sill height

Window Openings

Masonry opening width = door opening width + 4 in. (102 mm)

2 in. (51 mm) framing Masonry opening height = door opening height + 2 in. (51 mm)

2 in. (51 mm) framing 2 in. (51 mm) framing

Door Openings Figure 2—Modular Wall Openings 118

dards) allow placement without the need for sorting the product for quality—an activity that reduces overall productivity. Jobsite A quality jobsite helps productivity by including ample space for the mason subcontractor to work and having easy access to the masonry supplies. This includes having: • undisturbed space for building the sample panel(s), • a defined and ample-sized area for materials and supplies, and • a defined and ample-sized area for sampling and testing procedures as required for the project. Proper Installation In addition to the factors cited above, quality installation requires: • an ample number of qualified craftsmen, • qualified and sufficient supervision, and • the right equipment for the job. There have been some marvelous developments in products and equipment to assist masons and hence increase masonry productivity. For example, newer fork lifts often have increased capacity, a single boom which increases visibility, are more maneuverable, have higher load ratings and higher extensions. Other equipment advances that can enhance productivity include portable hand-held lasers that work in numerous directions simultaneously, electric portable winches and power (crank-up or hydraulic) scaffolding. Products that are easier for the mason to install, such as

self-adhesive flashings and pre-formed flashing end dams, can also impact masonry productivity. Choice of mortar can also impact productivity. Masonry and mortar cements provide more consistency because all of the cementitious ingredients are premixed. Premixed mortars, which include the sand mixed with the appropriate cement, are also available in silos or in mixers or blenders. Premixed mortars can improve mortar quality control and uniformity and can also increase productivity by eliminating the need for job site mixing. In some cases, work by other trades can also impact masonry productivity. For example, poured concrete foundations or footings which do not meet their tolerances may require the mason to saw-cut the first course of block, or take some other measure, to compensate. REFERENCES 1. Building Code Requirements for Masonry Structures, ACI 530-02/ASCE 5-02/TMS 402-02. Reported by the Masonry Standards Joint Committee, 2002. 2. Specification for Masonry Structures, ACI 530.1-02/ ASCE 6-02/TMS 602-02. Reported by the Masonry Standards Joint Committee, 2002. 3. All-Weather Concrete Masonry Construction, TEK 31C. National Concrete Masonry Association, 2002. 4. Kolkoski, R. V. Masonry Estimating. Craftsman Book Company, 1988. 5. Research Investigation of Mason Productivity. National Concrete Masonry Association, 1989.

Provided by:





ESTIMATING CONCRETE MASONRY MATERIALS

TEK 4-2A Costs/Estimating

Keywords: concrete masonry units, construction, estimating, grout, mortar

INTRODUCTION Estimating the quantity or volume of materials used in a typical masonry project can range from the relatively simple task associated with an unreinforced single wythe garden wall, to the comparatively difficult undertaking of a partially grouted multiwythe wall coliseum constructed of varying unit sizes, shapes, and configurations. Large projects, due to their complexity in layout and detailing, often require detailed computer estimating programs or an intimate knowledge of the project to achieve a reasonable estimate of the materials required for construction. However, for smaller projects, or as a general means of obtaining ballpark estimates, the rule of thumb methods described in this TEK provide a practical means of determining the quantity of materials required for a specific masonry construction project. It should be stressed that the information for estimating materials quantities in this section should be used with caution and checked against rational judgment. Design issues such as non-modular layouts or numerous returns and corners can significantly increase the number of units and the volume of mortar or grout required. Often, material estimating is best left to an experienced professional who has developed a second hand disposition for estimating masonry material requirements.

(203 mm) and nominal lengths of 16 in. (406 mm), the exposed surface area of a single unit in the wall is 8/9 ft 2 (0.083 m 2). Including a 5 percent allowance for waste and breakage, this translates to 119 units per 100 ft 2 (9.29 m2) of wall area. (See Table 1 for these and other values.) Because this method of determining the necessary number of concrete masonry units for a given project is independent of the unit width, it can be applied to estimating the number of units required regardless of their width. When using this estimating method, the area of windows, doors and other wall openings needs to be subtracted from the total wall area to yield the net masonry surface. Similarly, if varying unit configurations, such as pilaster units, corner units or bond beam units are to be incorporated into the project, the number of units used in these applications need to be calculated separately and subtracted from the total number of units required.

ESTIMATING CONCRETE MASONRY UNITS

Unit Unit face Number of units per type size, in. (mm) 100 ft2 (100 m2) of wall area conventional 8 x 16 (203 x 406) 119 (1,275) half-high 4 x 16 (102 x 406) 238 (2,550) half-length 8 x 8 (203 x 203) 238 (2,550) brick 22/3 x 8 (68 x 203) 710 (7,610)

Probably the most straightforward material to estimate for most masonry construction projects is the units themselves. The most direct means of determining the number of concrete masonry units needed for any project is to simply determine the total square footage of each wall and divide by the surface area provided by a single unit specified for the project. For conventional units having nominal heights of 8 in.

ESTIMATING MORTAR MATERIALS Next to grout, mortar is probably the most commonly Table 1—Approximate Number of Concrete Masonry Units Required for Single Wythe Constructiona

a

based on net area of masonry wall, includes about 5% waste 120


(2004)

Table 2—Mortar Estimation for Single Wythe Concrete Masonry Walls

Mortar type & batch proportions Masonry cement: 8-70 lb (31.8 kg) bags masonry cement, 1 ton (907 kg) sandb Preblended mortar: 1-80 lb (36.3 kg) bag 1-3,000 lb (1,361 kg) bag Site-mixed mortarc : Portland cement-lime: Type M 1 ft 3 portland cement, 1/4 ft 3 hydrated lime, 33/4 ft 3 sand Type S 1 ft 3 portland cement, 1/2 ft 3 hydrated lime, 41/2 ft 3 sand Type N 1 ft 3 portland cement, 1 ft 3 hydrated lime, 6 ft 3 sand Type O 1 ft 3 portland cement, 2 ft 3 hydrated lime, 9 ft 3 sand Mortar cement: Type M 1 ft 3 portland cement, 1 ft 3 Type N mortar cement, 6 ft 3 sand, or 1 ft 3 Type M mortar cement, 3 ft 3 sand Type S 1/ 2 ft 3 portland cement, 1 ft 3 Type N mortar cement, 41/ 2 ft 3 sand, or 1 ft 3 Type S mortar cement, 3 ft 3 sand Type N or O 1 ft 3 Type N mortar cement, 3 ft 3 sand Masonry cement: Type M 1 ft 3 portland cement, 1 ft 3 Type N masonry cement, 6 ft 3 sand, or 1 ft 3 Type M masonry cement, 3 ft 3 sand Type S 1/ 2 ft 3 portland cement, 1 ft 3 Type N masonry cement, 41/ 2 ft 3 sand, or 1 ft 3 Type S masonry cement, 3 ft 3 sand Type N or O 1 ft 3 Type N masonry cement, 3 ft 3 sand a

b c

a

Approximate number of units that can be laid using one batch of mortar Conventional CMU: Brick-sized CMU: 240

1,000

16 420

50 1,550

38

187

46

225

62

300

93

450

62 31

300 150

46 31

225 150

31

150

62 31

300 150

46 31

225 150

31

150

Number of units can vary from those listed in the table, based on factors such as the skill level of the mason, nonmodular layouts, numerous returns and corners, etc. Values include nominal amounts for waste. Assumes face shell mortar bedding for conventional concrete masonry units and full bedding for brick-sized concrete masonry units. 1 ft 3 = 0.0283 m3. 1 ton (907 kg) damp loose sand = 25 ft 3 (0.71 m3) For conversion purposes, the following can be used: Portland cement: typical bag volume = 1 ft 3 (0.028 m3); typical bag weight 94 lb (42.6 kg); typical density 94 lb/ft 3 (1,506 kg/m3 ) Hydrated mason's lime: typical bag volume = 11/4 ft 3 (0.035 m3); typical bag weight 50 lb (22.7 kg); typical density 40 lb/ft 3 (641 kg/m3) Sand: 1 ft 3 is equivalent to about 7 shovelfuls; typical density of damp loose sand 80 lb/ft 3 (1,281 kg/m3) Masonry and mortar cement bag weights vary, although commonly: Type N masonry cements and mortar cements are packaged in 70 lb (31.8 kg) bags; Type S masonry cements and mortar cements are packaged in 75 lb (34.0 kg) bags; Type M masonry cements and mortar cements are packaged in 80 lb (36.3 kg) bags.

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misestimated masonry construction material. Variables such as site batching versus pre-bagged mortar, mortar proportions, construction conditions, unit tolerances and work stoppages, combined with numerous other variables can lead to large deviations in the quantity of mortar required for comparable jobs. As such, masons have developed general rules of thumb for estimating the quantity of mortar required to lay concrete masonry units. These general guidelines are as follows for various mortar types. Note that the following estimates assume the concrete masonry units are laid with face shell mortar bedding; hence, the estimates are independent of the concrete masonry unit width. Masonry cement mortar Masonry cement is typically available in bag weights of 70, 75 or 80 lb (31.8, 34.0 and 36.3 kg), although other weights may be available as well. One 70 lb (31.8 kg) bag of masonry cement will generally lay approximately 30 hollow units if face shell bedding is used. For common batching proportions, 1 ton (2,000 lb, 907 kg) of masonry sand is required for every 8 bags of masonry cement. If more than 3 tons (2,721 kg) of sand is used, add 1/2 ton (454 kg) to account for waste. For smaller sand amounts, simply round up to account for waste. This equates to about 240 concrete masonry units per ton of sand.

Portland cement lime mortar One 94 lb (42.6 kg) bag of portland cement, mixed in proportion with sand and lime to yield a lean Type S or rich Type N mortar, will lay approximately 62 hollow units if face shell bedding is used. This assumes a proportion of one 94 lb (42.6 kg) bag of portland cement to approximately one-half of a 50 lb (22.7 kg) bag hydrated lime to 4 1/4 ft 3 (0.12 m3) of sand. For ease of measuring in the field, sand volumes are often correlated to an equivalent number of shovels using a cubic foot (0.03 m3) box, as shown in Figure 1. ESTIMATING GROUT The quantity of grout required on a specific job can vary greatly depending upon the specific circumstances of the project. The properties and configuration of the units used in construction can have a huge impact alone. For example,

Preblended mortar Preblended mortar mixes may contain portland cement and lime, masonry cement or mortar cement, and will always include dried masonry sand. Packaged dry, the mortars typically are available in 60 to 80 lb (27.2 to 36.3 kg) bags or in bulk volumes of 2,000 and 3,000 lb (907 and 1,361 kg).

Figure 1—Measuring Mortar Sand Volume

Table 3—Grout Volume Estimation for Hollow Single Wythe Concrete Masonry Walls Volume of grout, ft3 per 100 ft2 of wall (m3 per 100 m2)a Grout spacing, in. (mm) 8 (203) 16 (406) 24 (610) 32 (813) 40 (1,016) 48 (1,219) 56 (1,422) 64 (1,626) 72 (1,829) 80 (2,032) 88 (2,235) 96 (2,438) 104 (2,642) 112 (2,845) 120 (3,048) a

6 in. (152 mm) 25.6 (7.8) 12.8 (3.9) 8.6 (2.6) 6.4 (2.0) 5.2 (1.6) 4.3 (1.3) 3.7 (1.1) 3.2 (1.0) 2.9 (0.9) 2.6 (0.8) 2.4 (0.7) 2.2 (0.7) 2.0 (0.6) 1.9 (0.6) 1.8 (0.5)

8 in. (203 mm) 36.1 (11.0) 18.1 (5.5) 12.1 (3.7) 9.1 (2.8) 7.3 (2.2) 6.1 (1.9) 5.2 (1.6) 4.6 (1.4) 4.1 (1.2) 3.7 (1.1) 3.3 (1.0) 3.1 (0.9) 2.8 (0.9) 2.6 (0.8) 2.5 (0.8)

Wall width: 10 in. (254 mm) 47.0 (14.3) 23.5 (7.2) 15.7 (4.8) 11.8 (3.6) 9.4 (2.9) 7.9 (2.4) 6.8 (2.1) 5.9 (1.8) 5.3 (1.6) 4.7 (1.4) 4.3 (1.3) 4.0 (1.2) 3.7 (1.1) 3.4 (1.0) 3.2 (1.0)

12 in. (305 mm) 58.9 (18.0) 29.5 (9.0) 19.7 (6.0) 14.8 (4.5) 11.8 (3.6) 9.9 (3.0) 8.5 (2.6) 7.4 (2.3) 6.6 (2.0) 5.9 (1.8) 5.4 (1.6) 5.0 (1.5) 4.6 (1.4) 4.3 (1.3) 4.0 (1.2)

14 in. (356 mm) 74.5 (22.7) 37.3 (11.4) 24.8 (7.6) 18.6 (5.7) 14.9 (4.5) 12.4 (3.8) 10.6 (3.2) 9.3 (2.8) 8.3 (2.5) 7.5 (2.3) 6.8 (2.1) 6.2 (1.9) 5.7 (1.7) 5.3 (1.6) 4.9 (1.5)

Assumes two-core hollow concrete masonry units and 3% waste. 122

units of low density concrete tend to absorb more water from the mix than comparable units of higher density. Further, the method of delivering grout to a masonry wall (pumping versus bucketing) can introduce different amounts of waste. Although the absolute volume of grout waste seen on a large project may be larger than a comparable small project, smaller projects may experience a larger percentage of grout waste. Table 3 provides guidance for the required volume of grout necessary to fill the vertical cells of walls of varying thickness. Additional grout may be necessary for horizontally grouting discrete courses of masonry. Note that walls constructed of 4-in. (102-mm) masonry units are not included in Table 3. Due to the small cell size and difficulty in adequately placing and consolidating the grout, it is not recommended to grout conventional 4-in. (102-mm) units. Tables 4 and 5 contain estimated yields for bagged preblended grouts for vertical and horizontal grouting, respectively. REFERENCES 1 . Kreh, D. Building With Masonry, Brick, Block and Concrete . The Taunton Press, 1998. 2 . Annotated Design and Construction Details for Concrete Masonry, TR 90B. National Concrete Masonry Association, 2003.

Table 4—Grout Estimation for Hollow Single Wythe Concrete Masonry Walls, Vertical Grouting with Preblended Grouta CMU size, in. (mm) 6 (152) 8 (203) 10 (254) 12 (305) a

Yield, number of cores 80 lb (36.3 kg) bag 3,000 lb (1,361 kg) bag 3.6 150 2.7 110 2.2 95 1.8 80

80 lb (36.3 kg) bag yields approximately 0.66 ft 3 (0.019 m3); 3,000 lb (1,361 kg) bag yields approximately 25 ft 3 (0.71 m3 ) Table 5—Grout Estimation for Hollow Single Wythe Concrete Masonry Walls, Horizontal (Bond Beam) Grouting with Preblended Grouta

CMU size, in. (mm) 6 (152) 8 (203) 12 (305) a

Yield, linear ft (m) 80 lb (36.3 kg) bag 3,000 lb (1,361 kg) bag 2.7 (0.823) 100 (30.48) 2.0 (0.609) 80 (24.38) 1.6 (0.488) 60 (18.29)

80 lb (36.3 kg) bag yields approximately 0.66 ft 3 (0.019 m3); 3,000 lb (1,361 kg) bag yields approximately 25 ft 3 (0.71 m3 )

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CONCRETE MASONRY VENEER DETAILS Keywords: architectural details, cavity walls, connectors, construction details, flashing, parapets, wall openings, wall ties, weep holes INTRODUCTION A wall constructed with two or more wythes of masonry can technically be classified in one of three ways, depending on how each individual wythe is designed and detailed. These three wall systems are composite, noncomposite or veneer walls. A true veneer is nonstructural—any contribution of the veneer to the wall’s out-of-plane load resistance is neglected. Building Code Requirements for Masonry Structures (ref. 1) defines veneer as a masonry wythe which provides the exterior finish of a wall system and transfers out-of-plane loads directly to the backing, but is not considered to add load resisting capacity to the wall system. Noncomposite walls, on the other hand, are designed such that each wythe individually resists the loads imposed on it. Bending moments (flexure) due to wind or gravity loads are distributed to each wythe in proportion to its relative stiffness. Composite walls are designed so that the wythes act together as a single member to resist structural loads. This requires that the two masonry wythes be connected by masonry headers or by a mortar or grout filled collar joint and wall ties to help ensure adequate load transfer between the two wythes. The primary function of anchored veneers is to provide an architectural facade and to prevent water penetration into the building. As such, the structural properties of veneers are neglected in veneer design. The veneer is assumed to transfer out-of-plane loads through the anchors to the backup system. Building Code Requirements for Masonry Structures Chapter 6 (ref. 1) includes requirements for design and detailing anchored masonry veneer. A masonry veneer with masonry backup and an air space between the masonry wythes is commonly referred to as a cavity wall. The continuous air space, or cavity, provides the wall with excellent resistance to moisture penetration and wind driven rain as well as a convenient location for insulation. This TEK addresses concrete masonry veneer with concrete masonry backup.

TEK 5-1B Details

(2003)

DESIGN CONSIDERATIONS Masonry veneers are typically composed of architectural units such as: concrete or clay facing brick; split, fluted, glazed, ground face or scored block; or stone veneer. Most commonly, anchored masonry veneers have a nominal thickness of 4 in. (102 mm), although 3 in. (76 mm) veneer units may be available as well. Although structural requirements for veneers are minimal, the following design considerations should be accounted for: crack control in the veneer, including deflection of the backup and any horizontal supports; adequate anchor strength to transfer applied loads; differential movement between the veneer and backup; and water penetration resistance. The continuous airspace behind the veneer, along with flashing and weeps, must be detailed to collect any moisture that may penetrate the veneer and direct it to the outside. A minimum 1 in. (25 mm) air space between wythes is required (ref. 1), and is considered appropriate if special precautions are taken to keep the air space clean (such as by beveling the mortar bed away from the cavity or by placing a board in the cavity to catch and remove mortar droppings and fins while they are still plastic). Otherwise, a 2 in. (51 mm) air space is preferred. As an alternative, proprietary insulating drainage products can be used. Although veneer crack control measures are similar to those for other concrete masonry wall constructions, specific crack control recommendations have been developed for concrete masonry veneers. These include: locating control joints to achieve a maximum panel length to height ratio of 11/2 and a maximum spacing of 20 ft (6,100 mm), as well as where stress concentrations occur; incorporating joint reinforcement at 16 in. (406 mm) on center; and using Type N mortar for maximum flexibility. See Crack Control for Concrete Brick and Other Concrete Masonry Veneers for more detailed information (ref. 3). Because the two wythes in a veneer wall are designed to be relatively independent, crack control measures should be employed as required for each wythe. It is generally not necessary for the vertical movement joints in the veneer wythe to exactly align with those in the backup wythe, provided that the ties allow differential in-plane lateral movement. Wall ties may be joint reinforcement or wire wall ties. 124


Wall ties for veneers transfer lateral loads to the Slope to roof Wood nailer structural wythe and also allow differential inwith anchor bolt plane movement between wythes. This second Anchor bolt Fill solid at anchor feature is particularly important when the two bolt locations wythes are of materials with different thermal Sealant and moisture expansion characteristics (such as Sealant Concrete concrete masonry and clay brick), or in an Cant masonry veneer insulated cavity wall which tends to have Roofing membrane differential thermal movement between the Mesh or other Sealant wythes. When horizontal joint reinforcement is grout stop device Roofing membrane used to tie the two wythes together, hot-dipped Structural wythe as ladder type reinforcement is preferred over required by design Notch/pocket truss type, because the ladder shape Joint reinforcement accommodates differential in-plane and wall ties at movement and facilitates placing vertical 16 in. (406 mm) o.c., typ. reinforcement, grout and loose fill insulation. Because veneers rely on the backup for Insulation, Steel bar joist welded or as required support, wall ties must be placed within 12 in. bolted to bearing plate (305 mm) of control joints and wall openings to ensure the free ends of the veneer are Bond beam Mesh or other grout stop device adequately supported. More information on ties for veneers can be found in TEK 3-6B, Notes: Structural wythe of parapet must be a minimum of 8 in. (203 mm) Concrete Masonry Veneers (ref. 4). thick when empirical design is used (ref. 1). Rational design may allow a The distance between the inside face of the thinner wythe. Extending insulation up the full height of the parapet helps veneer and the outside face of the masonry prevent thermal losses through the parapet. backup must be a minimum of 1 in. (25 mm) and Figure 1—Parapet a maximum of 4 1/2 in. Sealant at top of Vapor retarder, (114 mm). For glazed flashing unless per local practice masonry veneer, beself-adhering cause of their imperInsulation, flashing is used or meable nature, a 2 in. as required tuck flashing into (51 mm) wide airmortar joint space is recomAirspace, 1 in. mended with air vents Finish varies (25 mm), min. at the top and bottom Concrete masonry Concrete masonry of the wall to enhance veneer backup drainage and help 1 in. (25 mm) weeps at Cavity filter or other equalize air pressure 32 in. (813 mm) o.c., mortar collection between the cavity partially open "L" device and the exterior of the shaped head joints wall. Vents can also be installed at the top Drip edge of other masonry veGrade neer walls to provide natural convective air Fill solid flow within the cavbelow flashing ity to facilitate drying. For vented caviConcrete slab ties, it is prudent to create baffles in the Waterproofing or Protective metal cavity at the building dampproofing on flashing foundation corners to isolate the cavities from each Insulation, Reinforcement, as other. This helps preas required required Grout vent suction being Note: Local codes may restrict the use of foam plastic insulation below grade in areas where the formed in the hazard of termite damage is very heavy. leeeward cavities. Figure 2—Foundation 125

Airspace, 1 in. (25 mm), min.

Vapor retarder, per local practice

Insulation, as required

Horizontal joint reinforcement at 16 in. (406 mm) o.c., typ.

Flashing

Concrete masonry backup Concrete masonry veneer 1 in. (25 mm) weeps at 32 in. (813 mm) o.c., partially open "L" shaped head joint

Concrete masonry lintel Finish varies

Drip edge

Ceiling support Cavity filter or other mortar collection device

Sealant Backer material Lateral support Window frame

Finish varies

Insulated glass

Sealant and backer material (a) Head

Window frame Min. slope 15°

Sealant Upside down lintel unit or solid unit

Concrete masonry sill unit or precast concrete sill

Flashing

Weeps 24 in. (610 mm) o.c. Drip edge 1 1 2 in. (38 mm) min. Concrete masonry veneer Airspace, 1 in. (25 mm), min.

Concrete masonry backup


Horizontal joint reinforcement at 16 in. (406 mm) o.c., typ.

Insulation, as required

(b) Sill

Figure 3—Window Opening 126

Concrete masonry veneer

Notes: In the backup wythe, the cell adjacent to the door should be filled solid. This is typically accomplished by slushing mortar into the cell as the wall is erected. A form board, or similar, is used at the edge of the cavity to confine the mortar or grout fill to the hollow metal jamb. For larger cavities where part of the cavity will not be covered by the door jamb, masonry units may be cut and mortared into place to provide a solid backing for the door jamb.

Insulation, as required Vapor retarder, per local practice Airspace, 1 in. (25 mm), min. Anchor, shape varies in mortar joint Form return-cut masonry or pressure treated wood blocking Caulk

Concrete masonry backup

Fill solid adjacent to door

Caulk Fill solid with mortar or grout

Figure 4—Metal Door Jamb REFERENCES 1. Building Code Requirements for Masonry Structures, ACI 530-02/ASCE 5-02/TMS 402-02. Reported by the Masonry Standards Joint Committee, 2002.

2. Annotated Design and Construction Details for Concrete Masonry, TR 90B. National Concrete Masonry Association, 2003. 3. Crack Control for Concrete Brick and Other Concrete Masonry Veneers, TEK 10-4. National Concrete Masonry Association, 2001. 4. Concrete Masonry Veneers, TEK 3-6B. National Concrete Masonry Association, 2003.

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CLAY AND CONCRETE MASONRY BANDING DETAILS

TEK 5-2A Details

(2002)

Keywords: architectural bands, architectural details, banding, clay brick, crack control, control joints, joint reinforcement, veneer, wall ties

INTRODUCTION

BANDING DETAILS

Masonry is often specified because of its aesthetic versatility. Combining masonry units of different size, color and finish provides a virtually limitless palette. Often, exterior concrete masonry walls incorporate clay brick, or concrete masonry is used in clay brick walls as accent bands. The bands add architectural interest to the wall and can also help hide horizontal elements such as flashing and expansion joints. However, combining these two materials within one wythe of masonry requires special detailing due to their different material properties. In general, all masonry walls should be designed and detailed to accommodate anticipated movement resulting from volume changes in the masonry materials themselves. For example, vertical control joints and horizontal joint reinforcement can be incorporated into concrete masonry walls to control cracking and still allow horizontal shrinkage of the concrete masonry units to occur without introducing undue stress into the wall. Similarly, clay masonry walls incorporate vertical and horizontal expansion joints to allow the clay to expand without distress. When both clay and concrete masonry units are used in the same masonry wythe, detailing is required to accommodate concrete masonry shrinkage and clay masonry expansion occurring side by side. Concrete masonry is a hydraulic cement product and as such requires water for cement hydration, which hardens the concrete. Therefore, concrete masonry units are relatively wet at the time of manufacture and from that time on tend to shrink as the units dry. Conversely, clay masonry units are very dry subsequent to firing during the manufacturing process and then tend to expand as they pick up moisture from the atmosphere and from mortar as they are laid. Without due consideration of these opposing movements, cracking can result. In veneers, the cracking is primarily an aesthetic issue, as any water that penetrates the veneer through cracks between the two materials drains down the cavity and is directed out of the wall via flashing and weep holes.

When detailing a wall to accommodate movement, the design goal is to allow the movement to occur (as restraint will cause cracking) while providing appropriate support. The recommendations that follow are based on a record of successful performance in many locations across the United States. These can be adjusted as needed to suit local conditions and/or experience. In general, several strategies are used to accommodate movement. These include movement joints (control joints in concrete masonry and expansion joints in clay masonry); horizontal joint reinforcement to take tension due to concrete masonry shrinkage and help keep any cracks that occur closed; and sometimes horizontal joints to allow longitudinal movement. In veneers, it is particularly important that the band, as well as the wall panel above and below the band be supported by wall ties. Wall ties should be installed within 12 in. (305 mm) of the top and bottom of the band to help ensure the surrounding masonry is adequately supported. In addition, using a lower compressive strength mortar helps ensure that if cracks do occur, they occur in the mortar joint rather than through the unit. Type N mortar is often specified for veneers, because it tends to be more flexible than other mortar Types. Concrete Masonry Band in Clay Brick Wall Figure 1a shows a two-course high concrete masonry band in a clay brick exterior wythe of a cavity wall. With this type of construction, the following practices are employed to minimize the potential for cracking. Horizontal joint reinforcement is placed in the mortar joints above and below the band to take stress from the differential movement in that plane. For bands higher than two courses, joint reinforcement should also be placed within the band itself at a spacing of 16 in. (406 mm) on center vertically. Ideally, the joint reinforcement and ties should be placed in alternate joints so that one does not interfere with


128

placement of the other. Some designers, Wall tie, within however, prefer placing joint reinforceVapor retarder, per 12 in. (305 mm) ment in every bed joint in the concrete local practice of band masonry band, particularly if the aspect ratio of the band is high. In this case, a tie Adjustable ladder Clay brick which accommodates both tie and wire wall tie (hot dipped galvanized) @ 16 in. in the same mortar joint should be used, (406 mm) o.c. vertical such as a seismic clip type wall tie. Joint reinforcement, Although the detail in Figure 1a has W1.7 (9 gage) demonstrated good performance in (MW 11) at Closed cell rigid many areas of the United States, there 16 in. (406 mm) insulation, as are locations where use of bond breaks o.c. or equivalent required at the top and bottom of the band is preferred (see Figure 1b) A local maConcrete masonry sonry industry representative should be Air space, 1 in. accent band (25 mm), min., contacted for further information on 2 in. (51 mm) which detail has been more successful in preferred a given location. Wall tie, within Figure 1b shows a slip plane incor12 in. (305 mm) porated into the interfaces between the of band concrete and clay masonry to allow unrestrained longitudinal movement be1a—with joint reinforcement at top and bottom of band tween the two materials. This can be accomplished by placing building paper, polyethylene, flashing or a similar mateWall tie, within Vapor retarder, per rial in the horizontal bed joints above and 12 in. (305 mm) local practice below the band. When hollow masonry of band units are used for the band, the slip plane Seismic clip-type Clay brick below the band should incorporate flashwall tie ing, so that any water draining down the Sealant and building cores of the band can be directed out of Closed cell rigid paper or other the wall at that point. insulation, as bond break material When slip planes are used, joint required Joint reinforcement reinforcement should be incorporated into the concrete masonry band. The Air space, 1 in. Concrete masonry exposed mortar joint at the top and bot(25 mm), min., accent band 2 in. (51 mm), tom of the band should be raked back and preferred sealed with an appropriate sealant to prevent water penetration at these joints. Note that this construction is typically Wall tie, within 12 in. (305 mm) more expensive than the detail shown in of band Figure 1a. In addition to joint reinforcement, 1b—with slip planes at top and bottom of band reduced spacing of expansion joints in the wall is recommended to reduce the Figure 1—Multi-Course Concrete Masonry Band in Clay Brick Veneer potential for cracking. Experience has shown that vertical expansion joints in the clay masonry reinforcement continuous through that joint. The continuous should extend through the concrete masonry band as well, and joint reinforcement in this location helps keep the clay brick be placed at a maximum of 20 ft (6.1 m) along the length of above and below the band from cracking as the concrete the wall. Although concrete masonry construction typically masonry shrinks. requires control joints rather than expansion joints, control Bands only one course high must be detailed to incorjoints should not be used in the concrete masonry band at the porate joint reinforcement and wall ties in the joints above expansion joint locations. and below the band (see Figure 2). Note that local experience may require reducing the When concrete masonry banding is used over a wood expansion joint spacing to 16 ft (4.9 m). If brick vertical stud backup, similar provisions apply (see Figure 3). It is expansion joint spacing does exceed 20 ft (6.1 m), consider imperative that joint reinforcement be used in the concrete placing an additional vertical movement joint through the masonry band, even if it is not used in the surrounding clay concrete masonry accent band near mid-panel with joint brick masonry.

129

Wall tie, within 12 in. (305 mm)

Vapor retarder, per local practice Seismic clip-type wall tie

Clay brick of band Concrete masonry accent band Joint reinforcement, W1.7 (9 gage) (MW 11) at 16 in. (406 mm) o.c. or equivalent Wall tie, within 12 in. (305 mm) of band

Closed cell rigid insulation, as required Air space, 1 in. (25 mm), min., 2 in. (51 mm), preferred

Figure 2—Single-Course Concrete Masonry Band in Clay Brick Veneer Wall tie, within 12 in. (305 mm) of band


Clay brick

Interior finish Sheathing

Joint reinforcement, W1.7 (9 gage) (MW 11) at 16 in. (406 mm) o.c. or equivalent Concrete masonry accent band

Wall tie, within 12 in. (305 mm) of band

Building paper, 6 in. (152 mm) min. lap Air space, 1 in. (25 mm), min.

Corrosion resistant 8d common nail, or one with equivalent pull-out strength

Figure 3—Concrete Masonry Band in Clay Brick Veneer Over Wood Stud Backup Wall tie, within 12 in. (305 mm) of band Concrete masonry Joint reinforcement, W1.7 (9 gage) (MW 11) at 16 in. (406 mm) o.c. or equivalent Clay brick accent band Wall tie, within 12 in. (305 mm) of band

Vapor retarder, per local practice Adjustable ladder wall tie (hot dipped galvanized) @ 16 in. (406 mm) o.c. vertical at 16 in. (406 mm) o.c., as required Closed cell rigid insulation, as required Air space, 1 in. (25 mm), min., 2 in. (51 mm), preferred

Clay Brick Band in Concrete Masonry Wall The recommendations to control differential movement for clay brick masonry bands in concrete masonry are very similar to those for a concrete masonry band in clay brick veneer: joint reinforcement above and below the band and wall ties within the band. Seismic clip-type wall ties are recommended, as they provide an adjustable wall tie and joint reinforcement in one assembly. With this construction, it is imperative that the veneer control joint not contain mortar as it goes through the clay brick band (see Figure 4). Mortar in this joint will restrict brick expansion, reducing the movement joint's effectiveness. Note that although control joints in structural masonry walls must permit free longitudinal movement while resisting lateral or out-ofplane shear loads, veneers are laterally supported by the backup and do not require a shear key. In single wythe construction as shown in Figure 5, flashing and weep holes are used above the accent band to facilitate removal of any water that may accumulate in the wall. The use of two reduced thickness concrete masonry units allows flashing to be placed within the wall without causing a complete horizontal bond break at the flashing. In reinforced walls (Figure 5b), flashing and weeps are also used. On the wall interior, rather than using reduced thickness units, a full size unit is cut to fit to allow adequate space for the reinforcement and grout. Vapor retarder, per local practice Closed cell rigid insulation Air space, 1 in. (25 mm) min., 2 in. (51 mm), preferred

Expansion joint

Adjustable tie

Sealant and No mortar backer rod in joint Expansion Joint Plan View for Clay Brick (Control joint in concrete masonry is similar, except it may contain a raked out mortar joint)

Figure 4—Multi-Course Clay Brick Band in Concrete Masonry Veneer

130

Cavity filter or other mortar collection device


4 in. (102 mm) thick concrete masonry unit

4 in. (102 mm) thick concrete masonry unit Flashing and weeps at 32 in. (813 mm) o.c., max.

Concrete masonry unit, nominal thickness = wall thickness - 4 in. (102 mm)

Flashing and weeps at 32 in. (813 mm), max., between grouted cells

Joint reinforcement

Clay brick accent band

Concrete masonry unit with one faceshell and part of webs cut off to fit Joint reinforcement


(a) unreinforced wall

(b) reinforced wall

Figure 5—Multi-Course Clay Brick Band in Loadbearing Concrete Masonry Wall

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NCMA TEK National Concrete Masonry Association an information series from the authority on concrete masonry technology

CLAY AND CONCRETE MASONRY BANDING DETAILS

CAN/TEK 5-2A Details (2003) Addresses Canadian construction practices, codes and standards

Keywords: architectural bands, architectural details, banding, clay brick, crack control, control joints, joint reinforcement, veneer, wall ties

INTRODUCTION

BANDING DETAILS

Masonry is often specified because of its aesthetic versatility. Combining masonry units of different size, color and finish provides a virtually limitless palette. Often, exterior concrete masonry walls incorporate clay brick, or concrete masonry is used in clay brick walls as accent bands. The bands add architectural interest to the wall and can also help hide horizontal elements such as flashing and expansion joints. However, combining these two materials within one wythe of masonry requires special detailing due to their different material properties. In general, all masonry walls should be designed and detailed to accommodate anticipated movement resulting from volume changes in the masonry materials themselves. For example, vertical control joints and horizontal joint reinforcement can be incorporated into concrete masonry walls to control cracking and still allow horizontal shrinkage of the concrete masonry units to occur without introducing undue stress into the wall. Similarly, clay masonry walls incorporate vertical and horizontal expansion joints to allow the clay to expand without distress. When both clay and concrete masonry units are used in the same masonry wythe, detailing is required to accommodate concrete masonry shrinkage and clay masonry expansion occurring side by side. Concrete masonry is a hydraulic cement product and as such requires water for cement hydration, which hardens the concrete. Therefore, concrete masonry units are relatively wet at the time of manufacture and from that time on tend to shrink as the units dry. Conversely, clay masonry units are very dry subsequent to firing during the manufacturing process and then tend to expand as they pick up moisture from the atmosphere and from mortar as they are laid. Without due consideration of these opposing movements, cracking can result. In veneers, the cracking is primarily an aesthetic issue, as any water that penetrates the veneer through cracks between the two materials drains down the cavity and is directed out of the wall via flashing and weep holes.

When detailing a wall to accommodate movement, the design goal is to allow the movement to occur (as restraint will cause cracking) while providing appropriate support. The recommendations that follow are based on a record of successful performance in many locations across the United States and typical Canadian conditions. These can be adjusted as needed to suit local conditions and/or experience. In general, several strategies are used to accommodate movement. These include movement joints (control joints in concrete masonry and expansion joints in clay masonry); horizontal joint reinforcement to take tension due to concrete masonry shrinkage and help keep any cracks that occur closed; and sometimes horizontal joints to allow longitudinal movement. In veneers, it is particularly important that the band, as well as the wall panel above and below the band be supported by wall ties. Wall ties should be installed within 300 mm (12 in.) of the top and bottom of the band to help ensure the surrounding masonry is adequately supported. In addition, using a lower compressive strength mortar helps ensure that if cracks do occur, they occur in the mortar joint rather than through the unit. Type N mortar is often specified for veneers, because it tends to be more flexible than other mortar Types. Concrete Masonry Band in Clay Brick Wall Figure 1a shows a two-course high concrete masonry band in a clay brick exterior wythe of a cavity wall. With this type of construction, the following practices are employed to minimize the potential for cracking. Horizontal joint reinforcement is placed in the mortar joints above and below the band to take stress from the differential movement in that plane. For bands higher than two courses, joint reinforcement should also be placed within the band itself at a spacing of 400 mm (16 in.) on center vertically. Ideally, the joint reinforcement and ties should be placed in alternate joints so that one does not 132

CAN/TEK 5-2A © 2003 National Concrete Masonry Association

interfere with placement of the other. Vapor barrier, per Wall tie, within Some designers, however, prefer placlocal practice 300 mm (12 in.) ing joint reinforcement in every bed of band Air barrier, (typical) joint in the concrete masonry band, particularly if the aspect ratio of the Clay brick band is high. In this case, a tie which accommodates both tie and wire in the Adjustable ladder same mortar joint should be used, such wall tie (hot dipped Joint reinforcement, as a seismic clip type wall tie. galvanized @ 400 W1.7 (9 gage) Although the detail in Figure 1a has mm (16 in.) o.c. (MW 11) at vertical demonstrated good performance in 400 mm (16 in.) many areas, there are locations where use o.c. or equivalent Closed cell rigid of bond breaks at the top and bottom of insulation as the band is preferred (see Figure 1b) A required Concrete masonry local masonry industry representative accent band should be contacted for further informaAir space, 25 mm tion on which detail has been more suc(1 in.), min. cessful in a given location. Wall tie, within Figure 1b shows a slip plane incorpo300 mm (12 in.) rated into the interfaces between the conof band crete and clay masonry to allow unrestrained longitudinal movement between 1a—with joint reinforcement at top and bottom of band the two materials. This can be accomplished by placing building paper, polyethylene, flashing or a similar material in Wall tie, within Vapor barrier, per the horizontal bed joints above and below 300 mm (12 in.) local practice of band the band. When hollow masonry units are Air barrier, used for the band, the slip plane below the Clay brick (typical) band should incorporate flashing, so that any water draining down the cores of the Sealant and building Seismic clip-type band can be directed out of the wall at that paper or other bond wall tie point. break material When slip planes are used, joint Joint reinforcement Closed cell rigid reinforcement should be incorporated insulation as into the concrete masonry band. The required Concrete masonry exposed mortar joint at the top and botaccent band tom of the band should be raked back and Air space, 25 mm sealed with an appropriate sealant to (1 in.), min. prevent water penetration at these joints. Wall tie, within Note that this construction is typically 300 mm (12 in.) more expensive than the detail shown in of band Figure 1a. In addition to joint reinforcement, 1b—with slip planes at top and bottom of band reduced spacing of expansion joints in the wall is recommended to reduce the Figure 1—Multi-Course Concrete Masonry Band in Clay Brick Veneer potential for cracking. Experience has shown that vertical expansion joints in the clay masonry reinforcement continuous through that joint. The continushould extend through the concrete masonry band as well, ous joint reinforcement in this location helps keep the clay and be placed at a maximum of 6.1 m (20 ft) along the length brick above and below the band from cracking as the of the wall. Although concrete masonry construction typiconcrete masonry shrinks. cally requires control joints rather than expansion joints, Bands only one course high must be detailed to incorpocontrol joints should not be used in the concrete masonry rate joint reinforcement and wall ties in the joints above and band at the expansion joint locations. below the band (see Figure 2). Note that local experience may require reducing the When concrete masonry banding is used over a wood expansion joint spacing to 4.9 m (16 ft). If brick vertical stud backup, similar provisions apply (see Figure 3). It is expansion joint spacing does exceed 6.1 m (20 ft), consider imperative that joint reinforcement be used in the concrete placing an additional vertical movement joint through the masonry band, even if it is not used in the surrounding clay concrete masonry accent band near mid-panel with joint brick masonry. 133

Wall tie, within 300 mm (12 in.) of band

Vapor barrier, per local practice Air barrier, (typical)

Clay brick Concrete masonry accent band Joint reinforcement, W1.7 (9 gage) MW 11) at 400 mm (16 in.) o.c. or equivalent

Seismic clip-type wall tie Closed cell rigid insulation as required Air space, 25 mm (1 in.), min.


Figure 2—Single-Course Concrete Masonry Band in Clay Brick Veneer Sealed air/vapor barrier, per local practice


Interior finish

Clay brick

Sheathing Joint reinforcement, W1.7 (9 gage) (MW 11) at 400 mm (16 in.) o.c. or equivalent

Building paper, 150 mm (6 in.) min. lap Air space, 25 mm (1 in.), min.

Concrete masonry accent band Wall tie, within 300 mm (12 in.) of band

Corrosion resistant 8d common nail, or one with equivalent pull-out strength

Figure 3—Concrete Masonry Band in Clay Brick Veneer Over Wood Stud Backup Wall tie, within 300 mm (12in.) of band Concrete masonry

Clay Brick Band in Concrete Masonry Wall The recommendations to control differential movement for clay brick masonry bands in concrete masonry are very similar to those for a concrete masonry band in clay brick veneer: joint reinforcement above and below the band and wall ties within the band. Seismic clip-type wall ties are recommended, as they provide an adjustable wall tie and joint reinforcement in one assembly. With this construction, it is imperative that the veneer control joint not contain mortar as it goes through the clay brick band (see Figure 4). Mortar in this joint will restrict brick expansion, reducing the movement joint's effectiveness. Note that although control joints in structural masonry walls must permit free longitudinal movement while resisting lateral or out-ofplane shear loads, veneers are laterally supported by the backup and do not require a shear key. In single wythe construction as shown in Figure 5, flashing and weep holes are used above the accent band to facilitate removal of any water that may accumulate in the wall. The use of two reduced thickness concrete masonry units allows flashing to be placed within the wall without causing a complete horizontal bond break at the flashing. In reinforced walls (Figure 5b), flashing and weeps are also used. On the wall interior, rather than using reduced thickness units, a full size unit is cut to fit to allow adequate space for the reinforcement and grout.

Vapor barrier, per local practice Air barrier, (typical)

Joint reinforcement, W1.7 (9 gage) (MW 11) at 400 mm (16 in.) o.c. or equivalent

Adjustable ladder wall tie (hot dipped galvanized @ 400 mm (16 in.) o.c.vertical at 400 mm (16 in.) o.c., as required


Closed cell rigid insulation as required


Air space, 25 mm (1 in.), min.

Vapor barrier, per local practice Air barrier, (typical) Closed cell rigid insulation Air space, 25 mm (1 in.), min.

Expansion joint

Adjustable tie

Sealant and No mortar in joint backer rod Expansion Joint Plan View for Clay Brick (Control joint in concrete masonry is similar, except it may contain a raked out mortar joint)

Figure 4—Multi-Course Clay Brick Band in Concrete Masonry Veneer 134

Cavity filter or other mortar collection device Concrete masonry unit, nominal thickness = wall thickness - 100 mm (4in.)

100 mm (4in.) thick concrete masonry unit Flashing and weeps at 800 mm (32 in.) o.c., max.

Joint reinforcement


100 mm (4 in.) thick concrete masonry unit

Concrete masonry unit with one faceshell and part of webs cut off to fit

Flashing and weeps at 800 mm (32 in.) max., between grouted cells Clay brick accent band

Joint reinforcement


(a) unreinforced wall

(b) reinforced wall

Figure 5—Multi-Course Clay Brick Band in Loadbearing Concrete Masonry Wall

ACKNOWLEDGMENT: The following assisted in the development of NCMA CAN/TEK for consistency with the National Building Code of Canada. Masonry Canada, 4628 10th Line, RR 2, Beeton, Ontario, Canada, L0G 1A0 (705) 458-9630. www.masonrycanada.ca For additional copies of CAN/TEK contact MC or NCMA at (705) 458-9630 or (703) 713-1900, respectively

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CONCRETE MASONRY FOUNDATION WALL DETAILS

TEK 5-3A Details

(2003)

Keywords: architectural details, basement wall, crawlspace wall, foundation wall, pier, plain concrete masonry, reinforced concrete masonry, residential details, stemwall INTRODUCTION Concrete masonry is used to construct various foundasulting from heaving caused by freezing of water in the soil. tion wall types, including full basement walls, crawlspace walls, Footings should be placed on undisturbed native soil, stem walls and piers. Concrete masonry is well suited for below unless this soil is unsuitable, weak or soft. In this case, the soil grade applications, because of its strength, durability, economy, should be removed and replaced with compacted soil, gravel or and resistance to fire, insects and noise. The modular nature of concrete. Similarly, tree roots, construction debris and ice concrete masonry allows floor plan and wall height changes Building paper to be easily accommodated as Sheathing well. Concrete masonry can be Flashing Floor sheathing used to provide a strong, duDrip edge rable, energy efficient and inSill, pressure treated or use moisture barrier sect resistant foundation for all Sealant building types. Anchor bolt Fill all voids This TEK contains details Concrete under flashing masonry wall for various types of concrete with mortar Grade masonry foundation walls, with Mesh or other accompanying text as approgrout stop device priate. The reader is referred to TEK 3-11, Concrete Masonry Waterproof or dampproof Basement Wall Construction, Insulation membrane Concrete masony wall TEK 19-3A, Preventing Water Horizontal joint Backfill Penetration in Below-Grade reinforcement, as Concrete Masonry Walls and required Free draining NCMA's Basement Manual for 1 2 in. (13 mm) isolation backfill more detailed design and conjoint Concrete slab struction information (refs. 2, 3, 4, respectively). Undisturbed Footings Footings lie under the basement, crawlspace or stem wall and transfer structural loads from the building to the supporting soil. Footings are typically cast-in-place concrete, placed beneath the frost depth to prevent damage re-

Vapor retarder

soil

Aggregate base Optional foundation drain Foundation drain

Full bed joint Concrete footing

Optional footing drain

Reinforcement, as required

Figure 1—Plain Basement Wall 136


should be removed prior to placing footings. Unless otherwise required, footings should be carefully aligned so that the concrete masonry wall will be near the center line of the footing. Although the top surface of poured concrete footings should be relatively level, it should generally not be troweled smooth, as a slightly roughened surface enhances the bond between the mortar and concrete. Concrete footing design is governed by Building Code Requirements for Structural Concrete, ACI 318 (ref. 5), and concrete foundations are constructed with tolerances conforming to the requirements of Standard Specifications for Tolerances for Concrete Construction and Materials, ACI 117 (ref. 9). BASEMENT WALLS Basements are typically built as conditioned space so that they can be used for storage, work or living space. Because of this, water penetration resistance is of paramount importance to basement wall design and construction. Following recommended backfill procedures will help prevent basement wall cracking during this operation. Walls should always be properly braced to resist backfill soil loads or have the first floor diaphragm in place prior to backfilling. Otherwise, a wall designed to be supported at the top may crack or even fail from overstressing the wall. Similarly, heavy equipment, such as bulldozers or cranes, should not be operated over

Flashing Drip edge Sealant Fill all voids under flashing with mortar Grade

the backfill during construction unless the basement walls are appropriately designed for the higher resulting loads. The top 4 to 8 in. (102 to 203 mm) of backfill should be low permeability soil so rain water absorption into the backfill is minimized. Finished grade should be sloped away from the building. Control joints are not typically used in foundation walls due to concerns with waterproofing the joint and the fact that shrinkage is less significant in below grade walls due to relatively constant temperature and moisture conditions. If warranted, horizontal joint reinforcement can be installed as a crack control measure. The foundation drain shown in Figures 1 and 2 can also be located on the interior side of the footing, or on both sides if necessary. The drain should be placed below the top of the footing. The optional footing drain shown, such as 2 in. (51 mm) PVC pipe at 8 ft (2400 mm) on center, allows water on the interior to reach the foundation drain. Footing drains can either be cast into the footing or constructed using plastic pipes through the bottom of the first course of masonry, directly on top of the footing. For reinforced construction (Figure 2), reinforcing bars must be properly located to be fully functional. In most cases, vertical reinforcement is positioned towards the interior face of below grade walls to provide the greatest resistance to soil pressures. A solid top course on the below grade concrete masonry wall Building paper spreads loads from the building Sheathing above and also improves soil gas and termite resistance. Where only Floor sheathing the top course is to be grouted, Sill, pressure treated or wire mesh or another equivalent use moisture barrier grout stop material can be used to contain the grout to the top course. Anchor bolt Note that local codes may reReinforced bond strict the use of foam plastic insubeam lation below grade in areas where Vertical reinforcement, the hazard of termite damage is high. as required

Grout Backfill


Waterproof or dampproof membrane

Vertical reinforcement, as required Horizontal joint reinforcement, as required Isolation joint Concrete slab Vapor retarder Optional foundation drain

Foundation drain Free draining backfill Undisturbed soil Concrete footing


Figure 2—Reinforced Basement Wall

Optional footing drain

STEMWALLS FOR CRAWLSPACES Unlike basements, crawlspaces are typically designed as unconditioned spaces, either vented or unvented. Several alternate crawlspace constructions are shown in Figures 3 and 4. Although most building codes require operable louvered vents near each corner of a crawl space to reduce moisture buildup, research has shown that the use of a moisture retardant ground cover eliminates the need for vents in many locations (ref. 6). If the crawlspace is vented, the 137

Vertical reinforcement, as required Horizontal joint reinforcement, as required

Continuous band joist or blocking, pressure treated or use moisture barrier Finish varies

Floor joist


Reinforced bond beam, as required Grade Bottom of footing minimum 12 in. (305 mm) below grade or below frost line, whichever is greater

Floor sheathing

Sill, pressure treated or use moisture barrier Termite shield required when no bond beam is provided below sill Anchor bolt

Concrete masonry stem wall

Install drain for water removal if not higher than adjacent exterior grade for majority of perimeter Vapor retarder

Concrete footing Bottom of footing


Figure 3—Crawlspace Stemwall with Masonry Above Grade floor, exposed pipes and ducts are typically insulated. If unvented, either the walls or the floor above can be insulated. Unvented crawlspaces must have a floor covering to minimize moisture and, where applicable, soil gas entry. A vapor retarder (typically 6-mil (0.15 mm) polyethylene, PVC or equivalent) is good practice to minimize water migration and soil gas infiltration. A 2 1/2 in. (64 mm) concrete mud slab is generally used when a more durable surface is desired for access to utilities. A thicker concrete slab may be desirable, particularly if the crawlspace will be used for storage. A dampproof coating on the exterior crawlspace wall will also help prevent water entry into the crawlspace. STEMWALLS FOR SLAB ON GRADE A stemwall with slab on gradesupports the wall above and often also provides a brick ledge to support an exterior masonry veneer. Figures 5 and 6 show concrete masonry stemwalls with masonry and with frame above grade walls, respectively. Because the wall is exposed to soil on both sides, waterproofing or dampproofing coatings are generally not required. Stemwalls are typically insulated on the exterior of the masonry. If insulated on the interior, it is important to place insulation in the joint between the slab edge and the foundation wall to avoid thermal bridging. A stemwall with brick ledge is shown in Figure 6. For this

case, note that masonry design codes typically require a minimum 1 in. (25 mm) clear air space between the masonry and backup to ensure an open drainage cavity. A 1 in. (25 mm) air space is considered appropriate if special precautions are taken to keep the air space clean (such as by beveling the mortar bed away from the cavity or by drawing a piece of wood up the cavity to collect mortar droppings). Otherwise, a 2 in. (51 mm) air space is preferred. FOUNDATION PIERS Foundation piers (see Figure 7) are isolated structural elements used to support the building above. Structural design ensures the piers are sized and spaced to carry the necessary building loads. Piers typically are in enclosed crawlspaces, so recommendations for moisture and soil gas resistance for crawlspaces should be followed for piers as well. Building Code Requirements for Masonry Structures (ref. 7) requires a foundation pier to have a minimum nominal thickness of 8 in. (203 mm), with a nominal height not exceeding four times its nominal thickness and a nominal length not exceeding three times its nominal thickness. Note that the International Building Code, (ref. 8) allows foundation piers to have a nominal height up to ten times the nominal thickness if the pier is solidly grouted, or four times the nominal thickness if it is not solidly grouted. 138

Stud

Water resistant sheathing

Finish varies

Brick veneer Wall tie

Floor sheathing

Continuous plate

Sill, pressure treated or use moisture barrier

1 in. (25 mm) air space, min. for drainage (note: 1 in. (25 mm) is maximum when corrugated ties are used)

Joist

Continuous band joist or blocking Building paper Anchor bolt Flashing, adhered to sheathing Weeps at 32 in. (813 mm) o.c. Fill solid below flashing

Termite shield, as required

18 in. (457 mm) min. Drain to daylight or install drain for water removal when below exterior grade

Grade

Concrete masonry

Vapor retarder

Bottom of footing minimum 12 in. (305 mm) below grade or below frost line, whichever is greater

Bottom of footing Reinforcement, as required

Concrete footing Finish varies

Exterior sheathing and finish Stud

Floor sheathing Joist

Sill, pressure treated or use moisture barrier

Termite shield, as required

Anchor bolt Mesh or other grout stop device Grade

Isolation joint 18 in. (457 mm) min. 2 1 2 in. (64 mm) concrete mud slab Install drain for water removal if not higher than adjacent exterior grade

Optional foundation drain Vapor retarder

Concrete footing



Bottom of footing Reinforcement, as required

Figure 4—Crawlspace Stemwalls with Wood Frame Above Grade 139


Concrete masonry wall Concrete masonry header unit

Isolation joint Concrete slab on grade with WWF

Concrete slab on grade with WWF Control joint, as required in concrete slab Vapor retarder Concrete footing Reinforcement, as required

Bottom of footing minumum 12 in. (305 mm) below grade or below frost line, whichever is greater

Vapor retarder Concrete footing Reinforcement, as required

Figure 5—Slab on Grade Stemwalls with Masonry Above Grade

Building paper Flashing Concrete slab on vapor retarder on 4 in. (102 mm) gravel

Perimeter insulation, as required

6 in. (152 mm) concrete masonry Concrete footing

Sheathing 1 in. (25 mm) air space, min. for drainage, (note: 1 in. (25 mm) is maximum when corrugated ties are used) Wall ties Drip edge Sealant Sill, pressure treated or use moisture barrier Anchor bolt Flashing (top adhered to backup) Weeps at 32 in. (813 mm) o.c.

10 in. (254 mm) solid concrete masonry top course, or grouted


Figure 6—Slab on Grade Stemwall with Wood Frame Above Grade 140

Sill plate Finish varies

Strap anchor nailed to girder and embedded in masonry

Sheathing

Joist hanger Joist Girder

Grout at strap anchor locations

Sill, pressure treated or use moisture barrier 8 in. (203 mm) nominal, min.

18 in. (457 mm) min.

Bottom of footing 12 in. (305 mm) below grade or below frost line, whichever is greater

Figure 7—Concrete Masonry Foundation Pier REFERENCES 1. Annotated Design and Construction Details for Concrete Masonry, TR 90A. National Concrete Masonry Association, 2002. 2. Concrete Masonry Basement Wall Construction, TEK 3-11. National Concrete Masonry Association, 2001. 3. Preventing Water Penetration in Below-Grade Concrete Masonry Walls, TEK 19-3A. National Concrete Masonry Association, 2001. 4. Basement Manual, Design and Construction Using Concrete Masonry, TR 149. National Concrete Masonry Association, 2001. 5. Building Code Requirements for Structural Concrete, ACI 318 -02. American Concrete Institute, 2002. 6. 2001 ASHRAE Handbook, Fundamentals. American Society of Heating, Refrigerating and Air-Conditioning Engineers, Inc., 2001. 7. Building Code Requirements for Masonry Structures, ACI 530-02/ASCE 5-02/TMS 402-02. Reported by the Masonry Standards Joint Committee, 2002. 8. International Building Code. International Code Council, 2000. 9. Standard Specifications for Tolerances for Concrete Construction and Materials, ACI 117-90. American Concrete Institute, 1990.

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CONCRETE MASONRY RESIDENTIAL DETAILS

TEK 5-4B Details

(2002)

Keywords: architectural details, energy conservation, residential, roof/wall connections, water penetration resistance INTRODUCTION Concrete masonry homes reflect the beauty and durability of concrete masonry materials. Masonry housing provides a high standard of structural strength, design versatility, energy efficiency, termite resistance, economy and aesthetic appeal. A wide range of architectural styles can be created using both architectural concrete masonry units and conventional units. Architectural units are available with many finishes, ranging from the rough-hewn look of split-face to the polished appearance of groundface units, and can be produced in many colors and a variety of sizes. Concrete masonry can also be finished with brick, stucco or any number of other finish systems if desired. Concrete masonry's mass provides many consumer benefits. It has a high sound dampening ability, is energy efficient, fire and insect proof, durable and can easily be designed to resist hurricaneforce winds and earthquakes.

Insulation, as required Roof deck + + + + o o

Exterior grade sheathing (vent as required)

Moisture barrier Embedded strap anchor (alternate: anchor bolt and top plate)

Bond beam Standard window system Sill

Finish varies Concrete masonry lintel

See TEK 19-5A for flashing details

Solid unit to support flashing

Wood backing, as required

Flashing with drip edge Insulation

Horizontal joint reinforcement, as required

Drainage layer

Vertical reinforcement as required

Concrete masonry wall Stucco

Isolation joint Concrete slab

Moisture barrier Flashing with drip edge Positive slope Vapor retarder

Perimeter insulation, as required

WALLTYPES Figures 1 through 3 illustrate a few of the construction options available for concrete masonry home construction, some of which are described in more detail below. Both top plate/anchor bolt and

Concrete masonry foundation Concrete footing


Figure 1—Stucco Exterior Finish 142


Roof system Roof insulation

Top plate, pressure treated or use moisture barrier (alternate: embedded strap anchor)

Finish varies Concrete masonry lintel

Soffit

Wood backing, as required Standard window system Furring and insulation, as required Sill

Vapor retarder, as required Solid unit to support flashing

See TEK 19-5A for flashing details Flashing with drip edge

Solid or filled unit to support flashing

1 in. (25 mm) partially open head joints for weeps at 32 in. (813 mm) o.c., max. between grouted cores

Sheathing Wood joist

See TEK 19-2A for flashing details

Joist hanger

Flashing with drip edge Ledger, pressure treated or use moisture barrier Bond beam

Anchor bolt Grade Horizontal joint reinforcement, as required

Insulation, as required Vertical reinforcement, as required

Backfill

Grout, as required Concrete masonry wall


Isolation joint

Foundation drain

Concrete slab Vapor retarder

Free draining backfill

Optional foundation drain

Undisturbed soil

Optional footing drain Concrete footing


Figure 2—Exposed Concrete Masonry Exterior 143

Roof system Roof insulation

Top plate, pressure treated or use moisture barrier (alternate: embedded strap anchor)

Finish varies

Soffit

Concrete masonry lintel Wood backing, as required

Standard window system

Furring and insulation, as required

Horizontal joint reinforcement, as required

Vapor retarder, as required



Subfloor

Siding

Positive slope

Floor joist Anchor bolt Bond beam

12 in. (305 mm) concrete masonry wall

Sill, pressure treated or use moisture barrier Install drain for water Vapor retarder removal if not higher than adjacent exterior grade for majority of perimeter

Concrete footing Reinforcement, as required

Figure 3—Wood or Vinyl Siding Exterior Finish 144

embedded strap anchor roof connections are shown and can be used interchangeably, along with several foundation types. See also TEK 5-7A Floor and Roof Connections to Concrete Masonry Walls and TEK 5-3A Concrete Masonry Foundation Wall Details (refs. 2, 3) for additional alternatives. Single wythe walls offer the economy of providing structure and an architectural facade in a single building element. They supply all of the attributes of concrete masonry construction with the thinnest possible wall section. To enhance the performance of this wall system, two areas in particular need careful consideration during design and construction—water penetration resistance and energy efficiency. Design for water resistance is discussed in detail in References 4 through 6. A full discussion of options for energy efficient concrete masonry walls is contained in Insulating Concrete Masonry Walls (ref. 7). The use of exterior finish systems lends itself to exterior insulation. Figure 1 shows an exterior insulation system, including a water drainage plane and stucco. Stucco can also be applied directly to the exterior block surface and used in conjunction with integral or interior insulation. Note that local codes may restrict the use of foam plastic insulation below grade in areas where the hazard of termite damage is high. Figure 2 shows a residential wall section with exposed concrete masonry on the exterior and a furred-out and insulated interior. Concrete masonry can be exposed on the interior as

well. In this case, integral insulation (placed in the masonry cores) can be used as required. Figure 3 shows exterior siding with insulation installed between furring. Wood or vinyl siding, as shown, is typically attached using exterior wood furring strips which have been nailed to the masonry. Cavity wall details are shown in TEK 5-1A Concrete Masonry Cavity Wall Details (ref. 8). REFERENCES 1. Annotated Design and Construction Details for Concrete Masonry, TR 90A. National Concrete Masonry Association, 2002. 2. Floor and Roof Connections to Concrete Masonry Walls, TEK 5-7A. National Concrete Masonry Association, 2001. 3. Concrete Masonry Foundation Wall Details, TEK 5-3A. National Concrete Masonry Association, 2003. 4. Water Repellents for Concrete Masonry Walls, TEK 19-1. National Concrete Masonry Association, 2002. 5. Design for Dry Single-Wythe Concrete Masonry Walls, TEK 19-2A. National Concrete Masonry Association, 2002. 6. Flashing Details for Concrete Masonry Walls, TEK 19-5A. National Concrete Masonry Association, 2000. 7. Insulating Concrete Masonry Walls, TEK 6-11. National Concrete Masonry Association, 2001. 8. Concrete Masonry Cavity Wall Details, TEK 5-1A. National Concrete Masonry Association, 1995.

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An

information

series

from

the

national

authority

on

concrete

INTEGRATING CONCRETE MASONRY WALLS WITH METAL BUILDING SYSTEMS

masonry

technology

TEK 5-5B

Details (2011)

typical details used for exterior concrete masonry cladding on a metal building. These details may need to be modified to meet individual design conditions. Because of the inherent material differences between steel and masonry, careful consideration must be given to accommodating differential movement between the two materials and their assemblies. In Serviceability Design Considerations for Low-Rise Buildings (ref. 2), a lateral drift limit of H/100 for a ten year recurrence wind loading based on main wind force resisting system loads is suggested for low rise buildings with exterior masonry walls reinforced vertically. See Table 12.12.1 of ASCE 7 (ref. 4) for the allowable story drift for seismic loading. Most reinforced masonry walls for metal buildings are designed to span vertically, supported by a steel spandrel at the top and by the foundation at the bottom.

INTRODUCTION

Roof purlin

Eave height

Metal buildings are used extensively for warehouses and other structures requiring large, open floor spaces. Part of their design flexibility comes from the ability to clad metal buildings with a variety of materials to provide different appearances or functions to the buildings. Concrete masonry walls are popular enclosure systems for metal buildings because of masonry's aesthetic appeal, impact resistance, strength, and fire resistance. The durability of concrete masonry resists incidental impacts from hand carts and forklifts, provides maximum protection in disasters such as earthquakes and hurricanes, as well as superior security, fire resistance, and noise control. Concrete masonry walls used for metal buildings can include: exterior full-height walls, either with or without a parapet; exterior partial-height or wainscot walls; and interior loadbearing walls or nonloadbearing walls or partitions. Ridge Architectural concrete masonry units, such as colored, split faced, burnished, or scored units, Roof System can be used to provide an almost limitless array Gutter of textures and patterns to the walls. These units can be used for the entire facade or for banding courses to achieve specific patterns or highlight certain design aspects of the building. A more detailed discussion of the system, along with structural design and construction considerations, is included in Concrete Masonry Walls for Metal Building Systems (ref. 1). The CMU wall manual is intended to bridge the gap between the Spandrel engineer who designs the metal building system Bracing and the engineer who designs the concrete masonry walls to unify their respective knowledge. DETAILS A typical metal building clad with masonry is shown in Figure 1. Figures 2 - 6 show some

Eave strut Rigid frame column Rigid frame

an

sp ar e l C Ba ys

pac ing

Sidewall

End wall frame End wall column End wall roof beam End wall End wall corner column

Figure 1—Schematic of Metal Building Clad with Concrete Masonry Walls

Keywords: anchorage, architectural details, cladding, connectors, construction details, deflection, drift, lateral loads, lateral support, metal building, shear walls, veneer, wall movement NCMA TEK 5-5B

146 1

Wall Base Because of stiffness and deforRigid frame column Concrete masonry mation incompatibilities between wall flexible steel and rigid masonry Flashing adhered to Extend foundation dowel 2 in. assemblies, and consequently, to concrete masonry (51 mm) into grouted cell of control the location of cracking in wall. Tape bar above flashing the masonry walls that may result "Hairpin" reinforcement to reduce bond to grout from relatively larger steel frame as required by design deflections at the top of the strucMastic seal around reinforcing bar ture, a “hinge” can be incorporated at the base of the masonry assembly to allow out-of-plane rotation. Continuous flashing Two such hinge connections with drip are shown in Figures 2 and 3. The construction shown in Figure 2 Column footing as Concrete column uses through-wall flashing to required by design break the bond at the base of the wall providing a simply supported Wall strip footing condition allowing shear transfer beyond but no moment for out-of-plane Footing loading. In many cases the shear reinforcement as force can be adequately transferred required by design by friction through the flashed bed joint. However, it is recommended Figure 2—Vertically Spanning Reinforced Concrete Masonry Side Wall at that a positive shear connection be provided by extending foundaFoundation for Other than Shear Wall Segment tion dowels across the joint. It is recommended that the number of bars extended across the horizontal joint be minimized, and that the extension be limited to 2 in. (51 mm), to ensure that the Concrete masonry wall Rigid frame column joint will behave as assumed. Therefore, every vertical Lap splice per design bar otherwise required for Flashing adhered to strength at critical sections concrete masonry Continuous flashing does not necessarily need to with drip "Hairpin" reinforcement be extended through the joint. as required by design Masonry shear walls are very strong and stiff Foundation dowel-extend past and are often used to resist flashing and lap with vertical reinforcement in masonry shear lateral loads. However, wall segment where required by masonry wall sections used design to maintain continuity and as shear wall segments must resist in-plane overturning forces have vertical reinforcement continuous into the foundaColumn footing as tion as shown in Figure 3. required by design Concrete column Flashing is also incorporated Wall strip footing at the floor level to allow beyond the wall some out-of-plane rotation due to building drift. Footing Design aids are included in reinforcement as Concrete Masonry Walls for required by design Metal Building Systems (ref. 1) for in-plane and out-ofplane reinforced masonry walls as well as for lintels Figure 3—Vertically Spanning Reinforced Concrete Masonry and anchor bolts. Appendix Side Wall Shear Wall Segment Detail at Foundation C also presents design ex2

147 NCMA TEK 5-5B

amples using NCMA’s popular, easy to use Structural Masonry Design System Software (ref. 3). As shown in Figure 4, these walls normally span vertically and are laterally supported by a spandrel at the top of the masonry portion of the wall. When the masonry is designed with a base hinge, it is important to properly detail the building corners to accommodate the movements. A vertical isolation joint should be placed near the building corner and proper consideration should be given to the masonry and steel connections at corner columns. Flexible anchors and/or slotted connections should be used. Wainscot Walls Although full height masonry walls provide the most benefit particularly when the masonry is used for shear walls, partial-height walls, or wainscots, are sometimes used. These walls are commonly 4 to 10 ft (1.2 to 3.0 m) high with metal panel walls extending from the top of the masonry to the roof. The masonry provides strength and impact resistance for the portion of the wall most susceptible to damage.

Rigid frame Bond beam Anchor bolts at 17 in. (432 mm) o.c., or 34 in. (864 mm) o.c. max. Reinforced bond beam at spandrel Grout cell at anchor bolt locations Mesh to confine grout Reinforced concrete masonry wall (reinforcement not shown for clarity)

Spandrel

Note: A standardized punching of 9/16 in. (14 mm) diameter holes at 17 in. (432 mm) centers for ½ in. (13 mm) masonry anchors is recommended The masonry engineer may choose to place the anchors farther apart than 17 in. (432 mm) o.c.; however, anchors should not be spaced more than 34 in. (864 mm) as this could affect lateral stability of the steel member being connected to prevent torsional buckling (ref. 1).

Column Detail Figure 5 shows the connection of a rigid frame column to concrete masonry sidewalls with a coincident vertical control joint. The Figure 4—Single Wythe Wall Without Parapet at details show vertically adjustable column anchors connecting the wall to the column. Low Side Wall or Eave (see also Figure 6) For walls designed to span vertically, it is good practice to provide a nominal number of anchors connecting the wall to the colRigid frame column umn to add stiffness and strength to the Vertical reinforcement edge of the wall. If rigid enough, these Inside flange brace as as required by wall anchors can assist in laterally bracing required by metal design the outside column flange. For larger building manufacturer lateral loads, more substantial connec(typ.) tions may be required. Anchorage to Anchor bolt (typ.) end wall columns is very similar. Spandrel Detail A typical spandrel detail is shown in Figure 6. Spandrels should be placed as high as possible to reduce the masonry span above the spandrel, especially on walls with parapets. Depending on the rigid frame configuration used, rigid frame connection plates and diagonal stiffeners may restrict the spandrel location. The spandrel is designed by the metal building manufacturer. If the inner flange of the spandrel needs to be braced, the metal building manufacturer will show on the drawings where the braces are required along with the inNCMA TEK 5-5B

Shim as required (typ.)

Contol joint Sash unit Preformed gasket Rake joint, fill with sealant on closed-cell backer rod

Grout cell at anchor location (typ.) Adjustable anchors

Figure 5—Adjustable Anchor Connection to Rigid Frame Column and Control Joint Detail 148 3

formation needed for the masonry engineer to design them and their anchorage to the wall. Shim plates should be used at spandrel/masonry connections to allow for camber in the spandrel and other construction tolerances (see Figure 6). The steel spandrel should never be pulled to the masonry wall by tightening the anchor bolts.

placement; concrete masonry foundation wall construction to grade; concrete slab placement; steel erection; and concrete masonry wall construction. Note, however, that this sequence may need to be modified to meet the needs of a particular project. For example, this construction sequence changes when loadbearing end walls are used. In this case, the steel supported by the masonry is erected after the masonry wall is in place. Coordination between the various trades is essential for efficient construction. Preconstruction conferences are an excellent way for contractors and subcontractors to coordinate construction scheduling and to avoid conflicts and delays.

CONSTRUCTION SEQUENCE Typically, construction of metal buildings with concrete masonry walls proceeds as follows: concrete footing and column

A

Anchor bolt Spandrel flange

21 2 in. (64 mm) min.

Concrete masonry wall Reinforced bond beam at spandrel. 6 in.(152 mm) min. grout on all sides of anchor which may require a two or more course high bond beam as shown Anchor bolt Spandrel Brace if required by metal building manufacturer (may be under spandrel or on top of spandrel)

Section A-A A

Shim plates as required Grout cell at anchor bolt for brace

Figure 6—Structural Spandrel for Lateral Load Detail REFERENCES 1. Concrete Masonry Walls for Metal Building Systems, TR 149A. National Concrete Masonry Association, Metal Building Manufacturers Association, International Code Council, 2011. 2. Serviceability Design Considerations for Steel Buildings, AISC Steel Design Guide #3. American Institute of Steel Construction, 2003. 3. Structural Masonry Design System Software. National Concrete Masonry Association, Western States Clay Products Association, The Brick Industry Association, and the International Code Council, 2010. 4. Minimum Design Loads for Buildings and Other Structures, ASCE 7-05. American Society for Civil Engineers, 2005.




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149 NCMA TEK 5-5B


CONCRETE MASONRY CURTAIN AND PANEL WALL DETAILS

TEK 5-6A Details

(2001)

Keywords: architectural details, construction details, curtain walls, high rise construction, nonbearing walls, panel walls, wall movement, veneer

INTRODUCTION Steel and concrete structural frames often rely on nonloadbearing masonry curtain or panel walls to enclose the structure. Panel and curtain walls are distinguished by the fact that a panel wall is wholly supported at each story, while a curtain wall is supported only at its base, or at prescribed interims. Both are designed to resist lateral wind or seismic loads and transfer these lateral loads to the structural frame. They typically do not carry any vertical loads other than their own weight. Curtain and panel walls differ from anchored masonry veneer in that veneer is continuously supported by a backup material. Curtain and panel walls must be isolated from the frame to prevent the unintentional transfer of structural loads and to allow differential movement between the frame and the masonry. Anchorage between the concrete masonry and structural frame must also account for different construction tolerances for each building material. Concrete masonry curtain and panel walls should incorporate flashing and weep holes as for other concrete masonry construction. Design for Dry Single-Wythe Concrete Masonry Walls, Flashing Strategies for Concrete Masonry Walls and Flashing Details for Concrete Masonry Walls (refs. 3, 4 & 5) provide detailed information.

however, to ensure proper bolt tension to avoid slipping once positioned. For high-rise construction, allowance should be made for differential movement between the shelf angle and the panel wall below due to creep of the frame and/or masonry thermal expansion. This is accomplished by leaving an open (mortarless) space between the bottom of the shelf angle and the masonry below or by filling the space with compressible

Anchor bolt

Cavity filter or other mortar collection device Weep holes at 32 in. (813 mm) o.c. Shelf angle Rigid insulation board Horizontal joint reinforcement as required

Rigid insulation board

PANEL WALLS Concrete masonry panel walls are supported at each building story by means of concrete beams, concrete slabs or steel members. Supports must take into account the strains and deformations in both the concrete masonry panel wall and the structural frame. Steel supports, often in the form of shelf angles, can be attached to the frame either by welding or bolting, although bolting is often preferred because slotted bolt holes permit adjustments to be made for proper alignment with the masonry. In addition, bolted connections are inherently more flexible than welded connections, allowing a limited amount of movement between the masonry and the frame. Care should be taken,

Air space Flashing

Sealant and backer Clearance Vapor retarder, per local practice

Air space Flashing Cavity filter or other mortar collection device

Steel anchor plate Shelf angle Horizontal joint reinforcement as required

Weep holes at 32 in. (813 mm) o.c. Sealant and backer Clearance Vapor retarder, per local practice

Figure 1—Shelf Angle Connections to Concrete 150


Rigid insulation board

Concrete column

Air space Flashing

Dovetail slot

Cavity filter or other mortar collection device Bolted anchor, welded to steel beam

Dovetail anchor

Weep holes at 32 in. (813 mm) o.c.

Adjustable channel slot anchor

Sealant and backer

Shelf angle

Clearance Horizontal joint reinforcement as required

Concrete column


Figure 2—Shelf Angle Connection to Steel Members material. The joint is then sealed with caulking to prevent moisture intrusion. The horizontal movement joint below the shelf angle also helps prevent vertical loads from inadvertently being transferred to the concrete masonry panel wall below the shelf angle. Flashing and weep holes should be installed immediately above all shelf angles to drain moisture. In multi-wythe panel walls, wall ties between the exterior and interior masonry wythes should be located as close to the shelf angle as possible. Figures 1 and 2 show steel shelf angle attachments to concrete and steel, respectively. CURTAIN WALLS Concrete masonry curtain walls can be designed to span either vertically or horizontally between supports. They can also incorporate reinforcement to increase lateral load resistance and the required distance between lateral supports. Anchors used to provide lateral support must be sufficiently stiff in the out-of-plane direction to transfer lateral loads to the frame and be flexible enough in-plane to allow differential movement between the curtain wall and the frame. In addition, Building Code Requirements for Masonry Structures (ref. 1) includes specific corrosion-resistance requirements to ensure long-term integrity of the anchors, consisting of AISI Type 304 stainless steel or galvanized or epoxy coatings. Anchors are required to be embedded at least 11/2 in. (38.1 mm) into the mortar bed when solid masonry units are used (ref. 1) to prevent failure due to mortar pullout or pushout. Because of the magnitude of anchor loads, it is also recommended that they be embedded in filled cores when using hollow units. As an alternative to completely filling the masonry core, this can be accomplished by placing a screen under the anchor and building up 1 to 2 in. (25 to 51 mm) of mortar into the core of the block above the anchor. For both concrete and steel frames, the space between the column and the masonry should be kept clear of mortar to avoid rigidly bonding the two elements together.

Figure 3—Curtain Wall Connections to Concrete Frames Figures 3 through 5 show curtain wall attachments to concrete and steel frames. CONSTRUCTION TOLERANCES Tolerances are allowable variations, either in individual component dimensions or in building elements such as walls or roofs. Construction tolerances recognize that building elements cannot always be placed exactly as specified, but establish limits on how far they can vary to help ensure the finished building will function as designed. When using masonry with another structural system, such as steel or concrete, construction tolerances for each material need to be accommodated, since construction tolerances vary for different building materials. In general, masonry must be constructed to tighter tolerances than those applicable to steel or concrete frames (refs. 2, 7). Particularly in high-rise buildings, tolerances can potentially affect anchor embedment, flashing details and available support at the shelf angle. To help accommodate these variations in the field, the following recommendations should be considered. • Use bolted connections with slotted holes for steel shelf angles to allow the shelf angle location to be adjusted to meet field conditions. Steel shims can be used to make horizontal adjustments to the shelf angle location. Figure 6 shows an example of a shelf angle connection which is adjustable in all three directions. For connections like this, the bottom flange needs to be evaluated for adequate load carrying capability as does the beam for torsion. • When shimming shelf angles, use shims that are the full height of the vertical leg of the shelf angle for stability. Shimming is limited to a maximum of 1 in. (25 mm) (ref. 7). • Provide a variety of anchor lengths to allow proper embedment over the range of construction tolerances. • Use two-piece flashing to accommodate varying cavity widths. • Cut masonry units only with the permission of the architect or engineer (this may be proposed when the frame cants 151

Fill cells of CMU solid with grout or mortar Horizontal joint reinforcement as required

Fill cells of CMU solid with grout or mortar Horizontal joint reinforcement as required

Steel column Adjustable anchor 1 in. (25 mm) min. clearance

Steel column Adjustable anchor 1 in. (25 mm) min. clearance

Notched steel adjustable anchor (typ) 1 in. (25 mm) min. clearance Preformed rubber control joint

Steel column

Fill cells of CMU solid with grout or mortar 1 in. (25 mm) min. clearance Horizontal joint reinforcement as required

Fill cells of CMU solid with grout or mortar Horizontal joint reinforcement as required (discontinue at control joint)

Steel column Adjustable anchor

Figure 4—Curtain Wall Connections to Steel Columns

Horizontal joint reinforcement as required 1 in. (25 mm) min. clearance Steel angle welded to beam Concrete slab on metal decking Steel beam

Sleeve

1 in. (25 mm) min. clearance Concrete slab

Horizontal joint reinforcement as required

Adjustable anchor

Adjustable anchor

Fill cell of CMU solid with grout or mortar

Fill cells of CMU solid with grout or mortar

Steel beam

1 in. (25 mm) min. clearance Concrete slab

Horizontal joint reinforcement as required

Steel angle welded to beam Concrete slab on metal decking

Steel beam Fill head joint solid with mortar

Strip anchor installed in masonry head joint (spot weld where anchor engages beam flange)

Figure 5—Curtain Wall Connections to Steel Beams 152

towards the masonry, making the cavity between the two materials too small). • Include instructions for handling building element misalignment in the construction documents.

Clip angle adjustability to maintain plumb

Adjustability for initial alignment

Adjustability to level shelf angle

Fig 6—Connection Adjustable in Three Directions

REFERENCES 1. Building Code Requirements for Masonry Structures, ACI 530-99/ASCE 5-99/TMS 402-99. Reported by the Masonry Standards Joint Committee, 1999. 2. Specification for Masonry Structures, ACI 530.1-99/ ASCE 6-99/TMS 602-99. Reported by the Masonry Standards Joint Committee, 1999. 3. Design for Dry Single-Wythe Concrete Masonry Walls, TEK 19-2A. National Concrete Masonry Association, 2001. 4. Flashing Strategies for Concrete Masonry Walls , TEK 19-4A. National Concrete Masonry Association, 2001. 5. Flashing Details for Concrete Masonry Walls, TEK 195A. National Concrete Masonry Association, 2000. 6. Laska, W. Masonry and Steel Detailing Handbook. The Aberdeen Group, 1993. 7. Code of Standard Practice for Steel Buildings and Bridges, American Institute of Steel Construction, Inc., 2000.

(ref. 6, z Hanley-Wood, reproduced with permission from Hanley-Wood, LLC)

Provided by:





DETAILING CONCRETE MASONRY FIRE WALLS

TEK 5-8B Details

(2005)

Keywords: architectural details, cantilevered fire wall, construction details, double fire wall, fire walls, fire-resistance rating, International Building Code, protected openings INTRODUCTION

FIRE WALLS

Concrete masonry, due to its inherent durability, reliability and superior fire resistance characteristics, is well suited to a range of fire protection applications. The International Building Code (IBC) (ref. 1) defines three wall types for fire protection— fire wall, fire barrier and fire partition—depending on the level of protection provided for the type of occupancy and intended use. Of the three defined fire-rated assemblies, a fire wall is generally considered to provide the highest level of robustness and fire safety. As such, it is intended to provide complete separation and must be structurally stable under fire conditions. Generally, fire barriers and fire partitions are required to provide the minimum protection necessary to assure that building occupants can evacuate a structure without suffering personal injury or loss of life. In addition to these requirements, fire walls reduce the likelihood of fire spread into the adjoining space, thus minimizing major property loss. Potentially significant architectural and economic advantages can be gained from using fire walls since each portion of a building separated by fire walls is considered a separate building for code compliance purposes. Designing and detailing fire walls is a complex task with many facets, including structural criteria, fire resistance, vertical and horizontal continuity, and criteria for protecting openings and joints. It is beyond the scope of this TEK to include every code provision and exception for fire wall design for all project conditions. While much of the information in this TEK is applicable to both the IBC and the NFPA 5000 (ref. 2) building codes, the provisions are based on the 2003 IBC, so certain provisions may be different from NFPA 5000 requirements. Hence, the information may or may not conform to local building code requirements and should be carefully reviewed to ensure compliance. In addition, the details shown here are not the only ones that will comply, but are included as examples. Project-specific needs will dictate the final detailing decisions.

By Code (ref. 1), fire walls are required to have the minimum fire-resistance rating acceptable for the particular occupancy or use group which they separate and must also have protected openings and penetrations. A fire wall must have both vertical and horizontal continuity to ensure that the fire does not travel over, under or around the fire wall. In addition, the wall must have sufficient structural stability under fire conditions to remain standing for the duration of time indicated by the fire-resistance rating even with the collapse of construction on either side of the fire wall. Fire-Resistance Rating Because fire walls provide a complete separation between adjoining spaces, each portion of the structure separated by fire walls is considered to be a separate building. Fire walls in all but Type V construction must be constructed of approved noncombustible materials. Table 1 shows minimum required fire-resistance ratings. Information on determining the fire-resistance ratings of concrete masonry assemblies is contained in Fire Resistance Rating of Concrete Masonry Assemblies, TEK 7-1A and Standard Method for Determining Fire Resistance of Concrete and Masonry Construction Assemblies (refs. 3, 4). Table 1—Required Fire Wall Fire-Resistance Ratings (ref. 1) Group Fire-resistance rating, hr A, B, E, H-4, I, R-1, R-2, U 3A B F-1, H-3 , H-5, M, S-1 3 H-1, H-2 4B F-2, S-2, R-3, R-4 2 A Walls shall not be less than 2-hour fire-resistance rated where separating buildings of Type II or V construction. B For Group H-1, H-2 or H-3 buildings, also see IBC Sections 415.4 and 415.5 154


Protected Openings and Penetrations The IBC states that fire walls must have closures such as fire doors or shutters which automatically activate to secure the opening in the event of a fire. Further, openings in fire walls are restricted to a maximum size of 120 ft2 (11.2 m2). An exception permits larger openings provided both buildings separated by the fire wall are equipped throughout with automatic sprinkler systems. In all cases, the aggregate width of all openings at any floor level is limited to 25 percent of the wall length. Through-penetrations in fire walls must utilize either fire-resistance-rated assemblies or a firestop system which is tested in accordance with either ASTM E 814 (ref. 5) or UL 1479 (ref. 6). The annular space between steel, iron or copper pipes or steel conduits and surrounding concrete masonry fire walls may be filled with concrete, grout or mortar for the thickness required to provide a fire-resistance rating equivalent to the fire-resistance rating of the wall penetrated. In addition, the penetrating item is limited to a 6-in. (152-mm) nominal diameter and the opening is limited to 144 in.2 (92,900 mm2). Openings for steel electrical outlet boxes are permitted provided they meet the Codespecified requirements. Combustible members, such as wood, are permitted to be framed into concrete masonry fire walls provided that, when framed on both sides of the wall, there is at least 4 in. (102 mm) between the embedded ends of the wood framing. The full thickness of the fire wall 4 in. (102 mm) above and below, as well as in between, the combustible member must be filled with noncombustible materials approved for fireblocking. Voids created at the junction of walls and floor/ceiling/ roof assemblies must be protected from fire passage by using fire-resistant joint systems tested in accordance with ASTM E 1966 or UL 2079 (refs. 7, 8). Control joints in fire walls must have fire-resistance ratings equal to or exceeding the required rating of the wall. Recommendations for locating and spacing control joints in concrete masonry walls also apply to concrete masonry fire walls. Control Joints for Concrete Masonry Walls, TEK 10-2B (ref. 9) includes control joint spacing criteria and illustrates control joint details for various fire-resistance ratings. Vertical and Horizontal Continuity The IBC mandates vertical continuity of a fire wall by requiring that the wall extend continuously from the foundation to a termination point at least 30 in. (762 mm) above both adjacent roofs. Exceptions permitting the fire wall termination at the underside of the roof deck or slab are listed in the Code. These exceptions require the use of Class B roof coverings (minimum), no openings within 4 ft (1.22 m) of the fire wall and other criteria for roof assembly protection. Buildings located over parking garages and stepped buildings are subject to additional requirements and permitted exceptions. Horizontal continuity limits the spread of fire around the ends of a fire wall. The IBC requires that fire walls be continuous from exterior wall to exterior wall and that they

extend at least 18 in. (457 mm) beyond the exterior surface of exterior walls. As with the vertical continuity requirements, there are criteria for terminating the fire wall at the interior surface of an exterior wall based on the types and fire-resistance ratings of the intersecting wall constructions and on the presence of an automatic sprinkler system installed per Code requirements. Structural Stability Under Fire Conditions While concrete masonry remains structurally stable during the extreme temperatures experienced under fire conditions, steel framing undergoes a reduction in strength as the surrounding temperature and duration of exposure are increased. This decreased structural capacity is evidenced by a dramatic increase in the deflection and twisting of steel members. Wood framing may burn, collapse, shrink and/or deform under fire exposure and it too loses its load-carrying capability. For these reasons, concrete masonry fire walls should be designed and detailed to withstand any loading imposed by fire-compromised framing systems or detailed so that those loads are not imparted to the fire wall during a fire. This is perhaps the most difficult detailing provision in fire wall design. DETAILING CONSIDERATIONS FOR STRUCTURAL STABILITY Because most fire wall criteria relating to fire-resistance rating, protected openings and penetrations, and vertical and horizontal continuity are prescriptive, the designer’s primary challenge when engineering and detailing a concrete masonry fire wall relates to maintaining the structural

Grout

Vertical reinforcement anchored in foundation Joint reinforcement, as required

Concrete masonry fire wall

Concrete masonry pilaster

Figure 1—Freestanding or Cantilevered Fire Wall with Pilaster 155

stability of the wall under fire conditions. There are various methods of designing, detailing and constructing fire walls for structural stability during a fire. Among the systems recommended for use as fire walls are: (a) cantilevered or freestanding walls, (b) laterally supported and tied walls, and (c) double wall construction. Cantilevered or Freestanding Walls Cantilevered walls (Figure 1) do not depend on the roof framing for structural support. The wall is cantilevered from the foundation by grouting and reinforcing, or by prestressing. Freestanding walls may also be designed to span horizontally between pilasters or masonry columns integral to the wall. It can be difficult to design a cantilevered single wythe loadbearing fire wall. Thermal stresses may cause deformation in steel or wood joists or framing systems which can eccentrically load the top of the fire wall. Designing the wall to remain stable under that loading condition may be difficult especially for tall or slender walls. For this reason, cantilevered single wythe fire walls are often designed as nonbearing walls with the primary roof framing system running parallel to the fire wall. Column lines on either side of the wall support the roof framing. Details for cantilevered/freestanding fire walls are similar to those for laterally supported walls (shown in Figures 2, 3 and 4) with the exception that cantilevered walls do not include through-wall ties or break-away connectors.

due to the collapse of the structure on one side of the fire wall are resisted by the structural framework on the other side of the wall. Adequate clearance, as listed in Table 2, between the framing and the concrete masonry fire wall is necessary to allow framing expansion or deformation without exerting undue pressure on the wall. Laterally supported fire walls may utilize break-away connectors manufactured with metals having melting points lower than structural steel (generally about 800° F (427° C)), so that, in the event of fire, the connectors on the fire side of the wall will give way before those on the non-fire side. In Figures 2 and 3, the structural diaphragm on the side of the wall opposite the fire provides the stability. The connections between the roof and wall must be designed to resist these forces. If the diaphragms occur at different elevations, the wall must be designed to withstand the anticipated flexural forces that will be generated as well. Figure 4 shows a laterally supported fire wall with combustible framing supported by metal joist hangers. Joist hanger manufacturers may have alternate details as well. Note that there may be code limitations on the use of combustible framing. Figure 5 shows design and detailing options for tied fire walls. Tied fire walls are a type of laterally supported fire wall where the roof structure is not supported by the fire wall, but rather by the roof structure on the other side

Parapet Fire stop material (not shown for clarity) between and around ends of joists

Laterally Supported or Tied Walls Laterally supported or tied walls rely on the building frame for lateral stability. The fire wall is laterally supported on each side by the framing system. As such, forces

Noncombustible roof deck with Class B roof covering 2 Bond beam

Table 2—Minimum Clearance Between Structural Steel and Fire Wall (ref . 10)

Length of bay perpendicular to fire wall ft. (m) 2 0 (6.1) 2 5 (7.6) 3 0 (9.1) 3 5 (10.7) 4 0 (12.2) 4 5 (13.7) 5 0 (15.2) 5 5 (16.8) > 60 (18.3)

Minimum clearance “X” between wall and steel, in. (cm) 2 1/2 (6.4) 3 1/4 (8.3) 3 3/4 (9.5) 4 1/2 (11.4) 5 (12.7) 5 3/4 (14.6) 6 1/4 (15.9) 7 (17.8) 7 1/2 (19.1)

Concrete masonry unit rated for fire exposure reinforced as required Steel bar joist each side

1

Notes: 1. Joists may be aligned if bond beam width permits proper installation of firestop material between joist ends. Stagger joists (as shown) as necessary. 2. 30 in. (762 mm) parapet is required unless all conditions are met: a) roof deck is noncombustible; b) roof covering is Class B (minimum); and c) no openings within 4 ft (1.22 m) of fire wall. 3. Top chord bearing wood joists similar. Figure 2—Laterally Supported Loadbearing Fire Wall 156

of the fire wall, thus the two roof structures are tied together across the fire wall. Figure 5a illustrates one choice for a “double column” detail which uses a through-wall tie to connect the primary steel on both sides of the fire wall. In this detail, the primary roof framing steel is parallel to the fire wall and supported on fireproofed columns. One column is used on each side of the fire wall to support the roof system for that building. Both steel columns and primary support beams/trusses should be aligned vertically and horizontally with the columns and beams/trusses on the opposite side of the wall and should be fireproofed. If the primary steel is not parallel to the fire wall Figure 5b shows a through-wall tie which can be used. As an alternative to using two steel columns, Figure 5c shows one steel support column encased entirely within the concrete masonry fire wall. Fire protection requirements for steel columns are included in Steel Column Fire Protection, TEK 7-6 (ref. 11). This system creates a single column line tied at the top of the wall to horizontal roof framing. Detailing the connection of the steel beams to the concrete masonry fire wall varies based on the framing layout, but the wall must be supported at the top and the connection must be fire protected. Double Wall Fire Wall Double wall construction (Figure 6) is generally easy to design and detail for loadbearing conditions, especially for taller walls. It utilizes two independent concrete masonry walls side by side, each meeting the required fire-resistance rating. In the event one wall is pulled down due to fire, the other wall remains intact, preventing fire spread. Floor and roof connections to each fire wall are the same as for conventional concrete masonry construction. These walls are often cantilevered or freestanding but may be tied or laterally supported as well if so detailed and designed. This system is also easy to use when a building addition requires a fire wall between the existing structure and the new construction.

Grout, as required Break-away connector each side

"X" each side see Table 2

Vertical reinforcement, as required Steel bar joist

Steel column each side


Note: If detailed without breakaway connectors, fire wall would be nonloadbearing freestanding or cantilevered. Figure 3—Laterally Supported Nonloadbearing Fire Wall

Parapet Fill full thickness of fire wall 4 in. (102 mm) above, below and between wood members with noncombustible fire blocking

Concrete masonry rated for fire exposure, reinforced as required Joist hangers bolted to concrete masonry

Note: Fire proofing (if required) not shown for clarity. Check with local building codes for fire rating requirements on wood truss and hanger assemblies. Figure 4—Laterally Supported Loadbearing Fire Wall: Wood Framing 157

Secondary steel

Primary steel

"X" both sides, see Table 2


Note: Beams and columns require fireproofing, not shown for clarity.

Figure 5a—Double Column Method, Through-Wall Tie Detail: Primary Steel Parallel to Fire Wall Concrete masonry fire wall

"X" both sides, see Table 2 Steel beam

Angle clip, weld to beam

A

Angle clip, weld to beam

Steel beam

A Section A - A

Provide clearance

Note: Beams and columns require fireproofing, not shown for clarity. Figure 5b—Double Column Method, Through-Wall Tie Detail: Primary Steel Perpendicular to Fire Wall

Masonry encases steel per building code

30 in. (762 mm) min. concrete masonry parapet

A

A

Steel beam framing into cross beam supported on steel column

Steel column encased in fire wall

Section A - A Concrete slab


Figure 5c—Single Column Method Figure 5—Tied Fire Walls (ref. 10) 158

REFERENCES Sheet metal coping cap with 1. International Building Code 2003. continous cleat each side International Code Council, 2003. Attachment strip 2. Building Construction and Safety Code – Wood nailer 2003 Edition, NFPA 5000. National Fire Counter flashing anchored to one wall Protection Association, 2003. Grout cores solid at anchor 3. Fire Resistance Rating of Concrete bolts and reinforcement Masonry Assemblies, NCMA TEK 7-1A. National Concrete Masonry Association, Sealant 2003. Bond Cant 4. Standard Method for Determining Fire beam Parapet flashing Resistance of Concrete and Masonry Construction Assemblies, ACI 216.1-97/ TMS 0216-97. American Concrete Institute and The Masonry Society, 1997. 5. Standard Test Method for Fire Tests of 90° hook Through-Penetration Fire Stops, ASTM E 814-02. ASTM International, 2002. 6. Fire Tests of Through-Penetration Firestops, UL 1479. Underwriters Steel bar joist welded Grout stop if wall Laboratory, 2003. or bolted to bearing below not grouted plate 7. Standard Test Method for Fire-Resistive Joint Systems, ASTM E 1966-01. ASTM Figure 6—Double Fire Wall International, 2001. 8. Tests for Fire Resistance of Building Joint Systems, UL 2079. Underwriters Laboratory, 2004 9. Control Joints for Concrete Masonry Walls–Empirical Method, NCMA TEK 10-2B. National Concrete Masonry Association, 2005. 10. Criteria for Maximum Foreseeable Loss Fire Walls and Space Separation, Property Loss Prevention Data Sheets 1-22. Factory Mutual Insurance Company, 2000. 11. Steel Column Fire Protection, NCMA TEK 7-6. National Concrete Masonry Association, 2003.

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CONCRETE MASONRY CORNER DETAILS

TEK 5-9A Details

(2004)

Keywords: architectural details, construction details, corners, modular coordination, unit shapes

INTRODUCTION A building's corners are typically constructed first, then the remaining wall section is filled in. Because they guide the construction of the rest of the wall, building the corners requires special care. It is essential that the corner be built as shown on the foundation or floor plan to maintain modular dimensions. For maximum construction efficiency and economy, concrete masonry elements should be designed and constructed with modular coordination in mind. Corners, however, present unique situations, because the actual widths of standard units are 3 5/8, 5 5/8, 7 5/8, 9 5/8 and 115/8 in. (92, 143, 194, 244 and 295 mm). In order to maintain an 8-in. (203-mm) module, special corner details have been developed to accommodate most typical situations.

Bay window or 8 in. (203 mm) 45° angle

45° Outside corner unit

Figures 2 through 6 show how corners can be constructed to minimize cutting of units while maintaining modularity of the construction. Vertical steel, while not always required, is often used at corner intersections. UNITS Unlike stretcher units, units used in corner construction have square ends (see Figure 1). In addition, all-purpose or kerf units are available, with two closely spaced webs in the center that allow the unit to be easily split on the jobsite, facilitating corner construction. Other special units may also be available, such as bevelled-end units, forming a 45° angle with the face of the unit, which are used to form walls

Double corner or plain-end unit

45° Inside corner unit

All-purpose, kerf or splitter unit

Single corner unit

Bevelled or mitered unit

Return corner unit

Figure 1—Concrete Masonry Units Used for Corner Construction TEK 5-9A © 2004 National Concrete Masonry Association (replaces TEK 5-9)

160

12 in. (305 mm) 15 5 (39 / 8in. 7m m)

. 5 8in ) 3 / mm (92

8 in. (203 mm)

. 5/ 8in 11 mm) 5 (29 3 5 (92 /8in mm . )

.

5/ 8in

e

35 (92 /8in mm . )

15 mm) 7 (39 35 (92 /8in mm . )

. 5/ 8in 15 mm) 7 (39 . 5 8in 7 / mm) 4 (19

15 5 (39 / 8in. 7m m)

it to t un Cu

12 in. (305 mm)

Corner return unit 75 (19 /8in 4m . m)

. 5 8in 3 / mm) (92

11 5 (29 / 8in. 5m m)

. 5 8in ) 3 / mm (92

fit

. 5 8in 7 / mm) 4 (19

15 5 (39 / 8in. 7m m) 7 5 (19 / 8in 4m . m)

. 5/ 8in 15 mm) 7 (39

Bevelled unit

Figure 2—Corner Details, 4 Inch (102 mm) Walls

Cut unit to fit or use nominal 14 in. (356 mm) units 8 in. (203 mm) 5 5 (14 / 8in 3m . m) 13 5 (34 / 8in. 6m m)

. 5/ 8in ) 3 1 mm 6 4 (3 . 5 8in 5 / mm) 3 (14

8 in. (203 mm) 15 (39 /58in 7m . (19 7 /58in m) 4m . m)

. 5 8in 7 / mm) 4 (19 . 5/ 8in ) 15 7 mm 9 3 (

8 in. (203 mm) Wall to 8 in. (203 mm) Wall Using Standard Units

Cut unit to fit or use nominal 14 in. (356 mm) units 15 (39 /58in. 7m m)

10 in. (254 mm) 7 5 (19 / 8in 4m . m) 15 5 (39 / 8in. 7m m)

. 5/ 8in 15 mm) 7 . (39 5 8in 7 / mm) 4 (19

Corner return unit


. 5/ 8in 15 mm) 7 (39

7 5 (19 / 8in. 4m m) 4 in. (102 mm) thick half-length unit

15 5 (39 / 8in. 7m m)

Alternate courses

. 5/ 8in 15 mm) 7 (39

. 5 in 7 / 8 m) m 4 (19 8 in. (203 mm) Wall to 12 in. (305 mm) Wall

Figure 4—Corner Details, 8 Inch (203 mm) Walls 161

6 in. (152 mm)

15 (39 /58in . 7m . 5 / 8 in m) 11 mm) 5 11 (29 5 in. /8 (29 /5 8in. 15 mm) 5m 7 m) (39

n. 5 8i 9 / mm) 4 (24

15 (39 /58in . 7 9 (24 /58 in mm) 4m . m)

. 5/ 8 in 11 mm) 5 (29

4 in. (102 mm)

. 5 8in / 15 mm) 7 (39

(for unreinforced corners only)

(for unreinforced corners only) 6 in. (152 mm)

15 (39 /58in n. 7m . 5 8i Cut unit to fit 9 / m) m) or use nominal m 4 9 /5 (24 5 8in. 14 in. (356 / 8 in (24 . 15 mm) Cut unit to fit mm) units 4m 7 9 m) (3 or use nominal 14 in. (356 mm) units (for unreinforced corners only)

11 (29 /5 8in 5m . m) 3 /5 (92 8in. mm )

6 in. (152 mm)

15 (39 /58 in 7m . m) (19 7 /58in 4m . m)

. 5 8in / 15 mm) 7 (39

1 5 8 x 5 5 8 x 7 5 8 in. (41 x 143 x 194 mm)

15 (39 /5 8in 7m . m)

15

n. 5 8i 7 / mm) 4 (19 5

8 x 5 8 x 7 8 in. (41 x 143 x 194 mm)

15 (39 /58in 7m . m)

15 (39 /58 in 7m . m)

Alternate courses

. / in 15 mm) 7 (39 5 8

(19 7 /58in 4m . m)

. 5 / 8 in ) 11 5 mm (29 n. 5 8i 7 / mm) 4 (19

. 5 8in / 15 mm) 7 (39

3 5/8 x 3 5/8 x 7 5/8 in. (92 x 92 x 194 mm)

. 5 8in / 15 mm) 7 (39

5

. 5 / 8 in ) 11 5 mm 9 (2

4 in. (102 mm)

n. 5 8i 7 / mm) 4 (19

15 (39 /58in. 7m (19 7 /58in m) 4m . m)

. 5 8in 3 / mm) 2 (9


15 (39 /5 8in. 7m m)

. 5/ 8in 15 mm) 7 (39 (19 7 /58in 4m . m)

Alternate courses

. 5/ 8in 15 mm) 7 (39

. 5 8in 7 / mm) 4 (19

Figure 6—Corner Details, 12 Inch (305 mm) Walls 162

intersecting at 135° angles. The Concrete Masonry Shapes and Sizes Directory (ref. 2) contains illustrations of additional corner units, including those with architectural surfaces. Units in adjacent courses overlap to form a running bond pattern at the corner. Architectural units, such as those with split or scored faces, are often available with the architectural finish on two sides to accommodate corner construction. Local manufacturers should be contacted for information on unit availability.

CODE PROVISIONS FOR INTERSECTING WALLS Building Code Requirements for Masonry Structures (ref. 4) stipulates three options to transfer stresses from one wall to another at wall intersections, each requiring the masonry to be laid in running bond. These three options are via: running bond; steel connectors; and bond beams. Corner

construction lends itself to providing shear transfer by relying on running bond. Running bond (defined as the placement of masonry units such that head joints in successive courses are horizontally offset at least one-quarter the unit length) ensures there is sufficient unit interlock at the corner to transfer shear. When any of these conditions are not met, the transfer of shear forces between walls is required to be prevented. REFERENCES 1 . Annotated Design and Construction Details for Concrete Masonry, TR 90B. National Concrete Masonry Association, 2003. 2 . Concrete Masonry Shapes and Sizes Directory, CM260A. National Concrete Masonry Association, 1997. 3 . Reinforced Concrete Masonry Inspector's Handbook, 4th edition. Masonry Institute of America, 2002. 4 . Building Code Requirements for Masonry Structures,ACI 530-02/ASCE 5-02/TMS 402-02. Reported by the Masonry Standards Joint Committee, 2002.

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CONCRETE MASONRY RADIAL WALL DETAILS

TEK 5-10A Details

(2006)

Keywords: construction details, curved walls, projection, radial walls, radius

r θ

O

Concrete masonry units are uniquely suited to distinctive aesthetically-pleasing architectural features. The almost limitless variety of sizes, shapes, textures, colors and surface treatments has made concrete masonry one of the most versatile and sought after building materials today. In addition, the relatively small unit size lends itself to unique applications, such as radial walls. The use of concrete masonry in the design and construction of radial walls presents a unique challenge to the design professional. Where curved walls once were formed from hand-hewn stone carved to fit a predetermined radius, radial walls of concrete masonry are usually formed from rectangular units of fixed shape and dimension. The end result is a series of short chords rather than a smooth arc. The greater the radius, the more closely the surface formed by the chords approaches that of a true arc. The curvature of these walls depends on variables such as the length and thickness of the concrete masonry unit, the width of the vertical head joints at the interior and exterior wall faces and whether the units will be used as is, beveled at the ends, or cut to conform to the desired radius. The bond pattern also impacts the overall appearance of a curved wall section. Curved walls laid up in stack bond (i.e., with vertical head joints aligned) possess the geometric properties of a regular polygon (Figure 1). Walls laid up in running bond (with offset head joints), on the other hand, exhibit a similar geometric configuration at the individual courses with the exception that the ends of units in alternating courses project out beyond the faces of the units immediately above and below (Figure 2). These projections create a basketweave effect which may or may not contribute to the aesthetic value of the wall. This TEK contains information to help the designer determine the best way to construct a curved concrete masonry wall, based on factors such as: desired radius, unit size, mortar joint size, projection size for running bond and the effect of cutting the units. Note that these recommendations apply to

S

INTRODUCTION

β A B

Figure 1—Plan View of Radial Wall Laid in Stack Bond (Regular Polygon) p

p

Figure 2—Plan View of Projections in Radial Wall as a Result of Running Bond 164


the physical limitations and geometry of constructing radial walls. The designer must ensure any radial wall design complies with all applicable building code requirements. Although this TEK focuses on the construction of radial walls using conventional concrete masonry units, note that beveled units or other special shapes may be available to facilitate masonry radial wall construction as well. MINIMUM WALL RADIUS The minimum radii for curved or circular walls constructed of concrete masonry units is determined through iterations of the plane rectilinear geometric formulae for regular polygons. These equations are: β = 2 (Tan -1 [(S1 - S2)/2t]) Eqn. 1 n = θ/β Eqn. 2 r = Sl /(2 Tan β/2) Eqn. 3 Example Nominal 8 x 8 x 16-in. (203 x 203 x 406-mm) concrete masonry units are being considered for use in a circular wall. Actual unit dimensions are 155/8 in. (397 mm) length and 75/8 in. (194 mm) width, and the exterior mortar joint is to be 3 /8 in. (9.5 mm). The width of the interior mortar joint is to be 1 /8 in. (3.2 mm). What is the smallest radius the circular wall can be constructed to without cutting the units? Step 1: Use Equation 1 to determine the angle β. Sl = 155/8 in. + 3/8 in. = 16 in. (406 mm) S2 = 155/8 in. + 1/8 in. = 153/4 in. (400 mm) t = 75/8 in. (194 mm) β = 2 (Tan -1 [(S1 - S2)/2t]) Eqn. 1 = 2 (Tan-1 [(16 - 15.75)/(2 x 7.625)]) = 2 Tan-l (0.0164) = 1.879o Step 2: Use Equation 2 to determine the number of units required. n = θ/β Eqn. 2 = 360/1.879o = 191.6 units Step 3: Adjusting n to be equal to a whole number, determine the required angle. n = θ/β Eqn. 2 192 = 360/β β = 360/192 = 1.875o Step 4: Use Equation 3 to determine the minimum wall radius. r = Sl /(2 Tan β/2) Eqn. 3 = 16/(2 Tan 0.9375) = 16/0.0327 = 489 in. = 40 ft.-9 in. (12.42 m) Although the equations remain the same, there are several practical methods to vary the minimum radii of curved or circular concrete masonry walls: • Reduce the length of the units. Changing from a 16-in. (406-mm) long unit to an 8-in. (203-mm) long unit will reduce the minimum radius by half.

•

Vary the mortar joint width. An increase in the mortar joint width at the exterior wall face, with or without a decrease in mortar joint width at the interior wall face, reduces the radius as well as the number of units required. Although it is generally recommended that the width of the mortar joint at the interior face not be less than 1/8 in. (3.2 mm), this may be acceptable under certain circumstances. • Shorten the length of the units at the interior face. Cutting the units is practical if stretcher units with flanged ends are used. Cutting is less practical for double corner units with plain ends (see Figure 3). Projections For a curved masonry wall laid in running bond, it may be desirable to limit the projections of the unit corners beyond the unit faces in the courses above and below for reasons of aesthetics. Generally, projections of approximately 1/8 in. (3.2 mm) for nominal 8 in. (203 mm) long units and 1/4 in. (6.4 mm) for nominal 16 in. (406 mm) long units are considered acceptable. If the wall surface is to be stuccoed or otherwise covered, projections of 1/2 in. to 3/4 in. (13 to 19 mm) may be acceptable. Minimizing projections to less than 1/8 in. (3.2 mm) is usually not practical because of construction tolerances. The projection of the unit corners for the previous example is found by using Equation 4. p = (S1/4) Sin β/2 Eqn. 4 = (16/4) Sin (0.9375) = 0.065 in. = 1/16 in. (1.6 mm) DESIGN TABLES Tables 1 through 6 list the minimum radii, number of units and length of projection for circular concrete masonry walls, based on using either a 3/8 in. (9.5 mm) or 1/2 in. (13

Stretcher unit - flanged ends

Double corner unit - plain ends Both ends are shown cut, although cutting only one end of each unit is also an option.

Figure 3—Concrete Masonry Unit Cuts to Facilitate Radial Wall Construction 165

Table 1—Minimum Radii: 8 in. (203 mm) Long Units (Uncut) Ext. mortar joint Nominal width 1 8 in. (3.2 mm) 8 in. (203 mm), nominal

Nominal unit width, in. (mm) 4 (102) 6 (152) 8 (203) 10 (254) 12 (305)

3

/8 in. (9.5 mm) Ext. mortar joint r, ft. (m) nA p, in. (mm) 1 9.75 (2.97) 92 /16 (1.6) 15.08 (4.59) 142 1/16 (1.6) 20.33 (6.20) 192 1/32 (0.79) 25.67 (7.83) 242 1/32 (0.79) 31.08 (9.48) 293 1/32 (0.79)

½ in. (25 mm) Ext. mortar joint r, ft. (m) nA p, in. (mm) 3 6.50 (1.98) 61 /32 (2.4) 1 10.08 (3.07) 95 /16 (1.6) 13.58 (4.14) 128 1/16 (1.6) 17.17 (5.24) 162 1/32 (0.79) 20.67 (6.30) 195 1/32 (0.79)

Table 2—Minimum Radii: 16 in. (406 mm) Long Units (Uncut) Ext. mortar joint Nominal width 1

in. (3.2 mm) 16 in. (406 mm), nominal 8


3

/8 in. (9.5 mm) Ext. mortar joint r, ft. (m) nA p, in. (mm) 1 19.50 (5.95) 92 /8 (3.2) 3 30.17 (9.20) 142 /32 (2.4) 40.75(12.43) 192 1/16 (1.6) 51.33(15.66) 242 1/16 (1.6) 62.17(18.96) 293 1/16 (1.6)

½ in. (25 mm) Ext. mortar joint r, ft. (m) nA p, in. (mm) 7 13.08 (3.99) 61 /32 (5.6) 1 20.33 (6.20) 95 /8 (3.2) 27.42 (8.36) 128 3/32 (2.4) 34.67(10.57) 162 3/32 (2.4) 41.75(12.73) 195 1/16 (1.6)

Table 3—Minimum Radii: 8 in. (203 mm) Long Cut Units (3/4 in. (19 mm) Cuts on Interior Face, One End Only) Ext. mortar joint Nominal width 1 in. (3.2 mm) 8 8 in. (203 mm), nominal


3

/8 in. (9.5 mm) Ext. mortar joint r, ft. (m) nA p, in. (mm) 9 2.42 (0.74) 23 /32 (7.1) 3 3.83 (1.17) 36 /16 (4.8) 1 5.08 (1.55) 48 /8 (3.2) 3 6.50 (1.98) 61 /32 (2.4) 3 7.83 (2.39) 74 /32 (2.4)

½ in. (25 mm) Ext. mortar joint r, ft. (m) nA p, in. (mm) 5 2.25 (0.69) 21 /16 (7.9) 3 3.42 (1.04) 32 /16 (4.8) 5 4.58 (1.40) 43 /32 (4.0) 1 5.75 (1.75) 54 /8 (3.2) 3 6.08 (1.85) 65 /32 (2.4)

Table 4—Minimum Radii: 16 in. (406 mm) Long Cut Units (3/4 in. (19 mm) Cuts on Interior Face, One End Only) Ext. mortar joint Nominal width 1 in. (3.2 mm) 8 16 in. (406 mm), nominal


3

/8 in. (9.5 mm) Ext. mortar joint r, ft. (m) nA p, in. (mm) 9 4.83 (1.47) 23 /16 (14) 7.67 (2.34) 36 11/32 (8.7) 1 10.17 (3.10) 48 /4 (6.4) 3 12.92 (3.94) 61 /16 (4.8) 3 15.67 (4.73) 74 /16 (4.8)

½ in. (25 mm) Ext. mortar joint r, ft. (m) nA p, in. (mm) 4.50 (1.37) 21 19/32 (15) 6.83 (2.08) 32 13/32 (10) 5 9.17 (2.80) 43 /16 (7.9) 1 11.58 (3.53) 54 /4 (6.4) 3 13.92 (4.25) 65 /16 (4.8)

Table 5—Minimum Radii: 8 in. (203 mm) Long Cut Units (3/4 in. (19 mm) Cuts Interior Face, Both Ends) Ext. mortar joint Nominal width 1 in. (3.2 mm) 8 8 in. (203 mm), nominal


3

/8 in. (9.5 mm) Ext. mortar joint r, ft. (m) nA p, in. (mm) 7 1.50 (0.46) 14 /16 (11) 5 1.25 (0.38) 21 /16 (7.9) 7 3.00 (0.92) 28 /32 (5.6) 3 3.75 (1.14) 35 /16 (4.8) 5 4.50 (1.37) 42 /32 (4.0)

½ in. (25 mm) Ext. mortar joint r, ft. (m) nA p, in. (mm) 1 1.33 (0.41) 13 /2 (13) 5 2.08 (0.63) 20 /16 (7.9) 1 2.75 (0.84) 26 /4 (6.4) 3 3.50 (1.07) 33 /16 (4.8) 5 4.25 (1.30) 40 /32 (4.0)

Table 6—Minimum Radii: 16 in. (406 mm) Long Cut Units (3/4 in. (19 mm) Cuts Interior Face, Both Ends) Ext. mortar joint Nominal width 1 in. (3.2 mm) 8 16 in. (406 mm), nominal

A


3

/8 in. (9.5 mm) Ext. mortar joint r, ft. (m) nA p, in. (mm) 7 2.92 (0.89) 14 /8 (22) 19 4.42 (1.35) 21 /32 (15) 7 5.92 (1.81) 28 /16 (11) 3 7.42 (2.26) 35 /8 (9.5) 5 8.92 (2.72) 42 /16 (4.0)

½ in. (25 mm) Ext. mortar joint r, ft. (m) nA p, in. (mm) 2.75 (0.84) 13 15/16 (24) 5 4.25 (1.30) 20 /8 (16) 1 5.58 (1.70) 26 /2 (13) 3 7.00 (2.14) 33 /8 (9.5) 5 8.50 (2.59) 40 /16 (4.0)

The value of n listed is for a full circle (θ = 360o). For θ < 360o, multiply n by θ/360. 166

mm) wide exterior head joint. Using the larger exterior head joint width allows for smaller radii. All tables assume that the interior head joint width is 1/8 in. (3.2 mm). Tables 1 and 2 present this data for 8 in. (203 mm) and 16 in. (406 mm) long units which have not been cut (as shown in Figure 3), respectively. Similar data for units cut as shown in Figure 3 are listed in Tables 3 through 6. Table 7 should be consulted when the size of the projection is a prime consideration. These tables list the minimum radii and number of units required to limit projections to 1/8 in. (3.2 mm) and 1/4 in. (6.4 mm) for nominal 8-in. (203 mm) and 16 in. (406 mm) long units. Construction and unit manufacturing tolerances are such Table 7—Minimum Radii for Curved Concrete Masonry Walls to Limit Projections 1

/8 in. (3.2 mm) Nominal unit maximum projection length, in. (mm) r, ft-in. (m) nA 8 (203) 5'-4" (1.63) 50 16 (406) 21'-4" (6.50) 101 A

1

/4 in. (6.4 mm) maximum projection r, ft-in. (m) nA 2'-9" (0.84) 25 10'-10" (3.30) 51

The value of n listed is for a full circle (θ = 360o). For θ < 360o, multiply n by θ/360.

that the radii provided in the Tables may vary by + 1 in. (25 mm). NOTATIONS n = Number of concrete masonry units to complete the arc for the central angle θ. The number of units for the arc should be a whole number. p = for masonry laid in running bond, projection of masonry unit corners beyond the faces of the units in the courses above and below (see also Figure 2), in. (mm) r = radius to the exterior face of the wall, measured to the midpoint of a unit, in. (mm) S1 = length of each side of the polygon forming the exterior face of the wall (length of the unit plus the width of one exterior mortar joint), in. (mm) S2 = length of each side of the polygon forming the interior face of the wall (length of the unit plus the width of one interior mortar joint), in. (mm) t = actual unit thickness, in. (mm) β = the angle subtended by one side of a polygon (length of one concrete masonry unit), see AOB in Figure 1, degrees θ = central angle subtended for the complete arc of the curved wall (equals 360o for a complete circle), degrees

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RESIDENTIAL DETAILS FOR HIGH WIND AREAS

TEK 5-11 Details

(2003)

Keywords: architectural details, construction details, continuous load path, high winds, reinforced concrete masonry, residential INTRODUCTION High winds subject buildings to large horizontal forces as well as to significant uplift. Reinforced concrete masonry is well suited to resist the large uplift and overturning forces due to its relatively large mass. High wind provisions generally apply to areas where the design wind speed is over 100 mph (161 km/hr) and over three second gust as defined by ASCE 7 (ref. 10). The enclosed details represent prescriptive minimum requirements for concrete masonry buildings, based on Standard for Hurricane Resistant Residential Construction (ref. 3). CONTINUOUS LOAD PATH Connections between individual building elements—roof, walls, floors and foundation—are critical to maintaining structural continuity during a high wind event. The critical

1 No. 5 (M #16) min. at each side of opening having a horizontal dimension greater than 6 ft (1,829 mm)

1 No. 5 (M # 16) min. at each end of shear segments Beams spanning openings

1 No. 5 (M #16) min. at each corner and at each change in wall direction

damage to buildings in such events typically occurs due to uplift on the roof, resulting in the loss of crucial diaphragm support at the top of the wall. A primary goal for buildings subjected to high winds is to maintain a continuous load path from the roof to the foundation. This allows wind uplift forces on the roof to be safely distributed through the walls to the foundation. If one part of the load path fails or is discontinuous, building failure may occur. Proper detailing and installation of mechanical connectors is necessary for maintaining continuous load paths. Note that in order for connectors to provide their rated load capacity, they must be installed according to the manufacturer’s or building code specifications. In coastal areas, corrosion protection is especially important due to the corrosive environment. Note that water penetration details are not specifically highlighted in the following details. The reader is

Shear segment 2 ft (610 mm) min.

Top course reinforced bond beam continuous around perimeter

Vertical wall reinforcement at 4 to 32 ft (1,219 to 9,745 mm) o.c. depending on wall height, design wind speed and roof span. Footing dowel not always required.

Standard 90° hook at each vertical bar, typ.

Footing dowels at corners, openings wider than 6 ft (1,829 mm) and ends of shear segments, min.

Figure 1—Typical Reinforcement for High Wind Areas 168


Engineered wood roof trusses or rafters at 24 in. (610 mm) o.c., max. Roof sheathing

Bond beam Standard hook extended 6 in. (152 mm) into bond beam (min.) at each vertical wall reinforcement, typ. 1

4 in. (6 mm) expansion joint material and sealant

Concrete slab

Truss anchor rated for vertical uplift and horizontal loads perpendicular and parallel to the wall

24 in. (610 mm) max. overhang Concrete masonry wall Vertical reinforcement, as required 40 bar diameter lap, min. for Grade 40, 48 bar diameters for Grade 60.

Grout, as required Reinforced concrete footing

Ceiling height

12 max.

3 ft (914 mm), max. 8 ft (2,438 mm) when top of stem wall is tied to slab (see Figure 3)

12

Figure 2—Exterior Loadbearing Wall Horizontal reinforcement, as required Concrete masonry bond beam unit with part of interior face shell removed

Concrete masonry wall Concrete slab with 6 x 6, W 1.4 x W 1.4 (152 x 152 mm, MW 9 x MW 9) WWF*, extending at least 10 ft (3,050 mm) into slab and at least 6 in. (152 mm) into masonry bond beam

referred to references 7 through 9 for more information on preventing water penetration in concrete masonry walls. In addition to a continuously reinforced bond beam at the top of the wall around the entire perimeter of the building, vertical reinforcement must be placed throughout a wall to resist the high uplift loads and provide continuity, including: at corners and wall intersections; on each side of openings wider than 6 ft (1,829 mm); at the ends of shear segments; and where girders or girder trusses bear on the concrete masonry wall (refs. 3, 4). Each of the exterior walls on all four sides of the building and all interior walls designed as shear walls must have at least one 2 ft (610 mm) minimum section of wall identified as a shear segment to resist the high lateral loads. Longer shear segments are more effective and are recommended where possible or required by design. See Figure 1 for a summary of reinforcement requirements (ref. 3). Reinforcement must be properly spliced to provide load path continuity. Using allowable stress design, a splice length of 40 bar diameters is required by Building Code Requirements for Masonry Structures (ref. 1) for Grade 40 reinforcement and 48 bar diameters for Grade 60 reinforcement. If the wall was designed assuming Grade 40 and Grade 60 was used for construction, however, the 40 bar diameter lap splice may still be used. See Steel Reinforcement for Concrete Masonry, TEK 12-4C (ref. 5) for standard hook requirements. DETAILS

8 ft (2,438 mm), max. Vapor retarder

* Alternate: use No. 3 minimum at 4 ft (M# 10 at 1,219 mm) o.c. maximum extending into slab 10 ft (3,050 mm) min. and hooked into bond beam Concrete footing Reinforcement, as required

Figure 3—Slab Connection for Foundation Wall 3 to 8 ft (914-2,440 mm) Above Grade

Exterior Loadbearing Wall Figure 2 shows a typical loadbearing wall with a floating floor slab. Vertical reinforcement should be placed in the center of the concrete masonry cores to adequately resist both positive and negative wind pressures. Bond beam depth and minimum horizontal reinforcement varies with design wind velocity, ceiling height, roof truss span and spacing of vertical wall reinforcement. Since wind suction forces on the leeward side of a building can be 169

essentially as high as the pressure forces on the windward side, limitations are placed on the height above grade. However, if the slab is laterally supported and tied to the concrete masonry foundation wall as shown in Figure 3, the foundation wall may be extended to 8 ft (2,440 mm) above grade (ref. 3). Roof Truss Anchor Figure 4 shows a typical roof truss anchor cast into the bond beam of a concrete masonry bearing wall. The required anchor load capacity depends on the design wind speed as well as the roof truss span. In addition to being rated for uplift, the anchor must be rated for horizontal forces parallel to the wall (in-plane) and perpendicular to the wall (out-of-plane). Often, the direct embedded roof truss anchor method of connecting the roof to walls is preferred over the bolted top plate and hurricane clip method, as it generally has greater capacity and fewer connections. Additionally, the nail area available for the hurricane clip is limited by the thickness of the top plate. Bolted Top Plate As an alternate to the roof truss anchor, a bolted top plate may be used for the roof to wall connection (see Figure 5); however, anchor bolt spacing must be reduced (24 in. (610 mm) maximum) because the top plate is loaded in its weak direction. The detail illustrates several different connector types that are commonly used to connect the truss to the top plate. Gable End Walls Because of their exposure, gable end walls are more prone to damage than are hipped roofs unless the joint at the top of the end wall and the bottom of the gable (see Figure 6b) is laterally supported for both inward and outward forces. Figure 6a shows a continuous masonry gable end wall using either a raked concrete bond beam or a cut masonry bond beam along the top of full height reinforced concrete masonry gable end walls. As an alternative, a braced gable end wall can be constructed as shown in Figure 6b by stopping the masonry of the gable end at the eave height and then using conventional wood framing to the roof diaphragm. However, unless the end wall is properly braced to provide the necessary lateral support as shown in Figure 6b, this results in a weak point at the juncture of the two materials with little capacity to resist the high lateral loads produced by high winds. The number and spacing of braces depends on design wind speed, roof slope and roof span (ref. 2, 3, 6).

Direct embedded roof truss anchor installed per manufacturers specifications

F1 F2

Roof truss at 24 in. (610 mm) o.c., max. Moisture barrier F3

Bond beam Grout stop Horizontal reinforcement, as required Concrete masonry wall

Note: F1, F2 and F3 are forces that must be accommodated in the design of the roof/wall connection. Figure 4—Roof Truss Anchor

Connector (typ.)

F2

F1

F3

Oversized washer per design, typ. Bond beam

Connector may be bent and prenailed on bottom side if additional nailing area is required

Pressure treated Southern pine #2 or better top plate, as required (2 x 4 min.)

1

2 in. (13 mm) anchor bolt at 18 to 24 in. (457 to 610 mm) o.c., or as required

Note: F1, F2 and F3 are forces that must be accommodated in the design of the roof/wall connection. Figure 5—Bolted Top Plate 170

Standard 90° hook with lap

Maintain minimum cover

4 in. (102 mm) min.

Reinforced cast-in-place or cut masonry rake beam at roof line

2 x 4 in. (38 x 89 mm) min. wood nailer with 1 2 in. (13 mm) anchor bolts

Foundation at one-story building or bond beam at multistory

6a—Continuous Gable End Wall Reinforcement 12 in. (305 mm) max.

8d nails at 6 in. (152 mm) o.c.

2 x 4 (38 x 89 mm) at 32 in. (813 mm) o.c., or as required

Facia Soffit

Uplift strap, 100 lb. (0.44 kN) at each stud or per design

2 (38 mm) x ladder framing at 24 in. (610 mm) o.c. max. 7

16 in. (11 mm) rated structural panels, 8d nails 6 in. ( 152 mm) o.c. at edges, 12 in. (305 mm) o.c. in field

1 Oversized washer 2 x 6 (38 x 140 mm), pressure treated or use moisture barrier 8d nails at 6 in. (152 mm) o.c. 8 in. (203 mm)

5 - 8d nails each side or 5 8 in. (16 mm) diameter thru-bolt

2 x 6 (38 x 140 mm) at 16 in. (406 mm) 2 - 8d toenails into brace o.c. 2 x 4 (38 x 89 mm) continuous nailed 1 to truss webs (one per truss) Double 2 x 4 (38 x 89 mm) at 32 in. (813 mm) o.c. (1 each side of stud) or as required 5 - 8d nails each side or 5 8 in. (16 mm) diameter thru-bolt Uplift strap, 100 lb (0.44 kN) at each stud or as required 1

2 in. (13 mm) anchor bolt at 48 in. (1,219 mm) o.c. or proprietary anchor

Bond beam

Note: brace can be similarly used with a sloped beam at the top of a masonry end wall that terminates at the bottom of a vaulted ceiling (i.e., scissors truss)

Mesh or other grout stop device Concrete masonry wall with vertical reinforcement as required

Joint in gable end wall

6b—Braced Gable End Wall Figure 6—Gable End Wall Construction 171

Pressure treated 2 x 4 (38 x 89 mm) at 24 in. (610 mm) o.c., max. Facia Soffit 24 in. (610 mm), max. overhang

Roof sheathing

Wood roof truss 8 in. (203 mm) concrete rake beam with 1 No. 5 (M #16) bar min. (4 in. (102 mm) minimum depth)

90° standard hook

Concrete masonry wall Vertical wall reinforcement, as required

Grout, as required

A

A

Grout stop location

7a—Section A-A, Concrete Rake Beam With Outlooker Type Overhang

12 in. (305 mm) max. overhang

Facia Soffit 2 x 4 (38 x 89 mm) at 24 in. (610 mm) o.c. max. 2 x 4 (38 x 89 mm) (min.) pressure treated wood nailer Standard hook with lap, typ.

1

2 in. (13 mm) anchor bolt at 3 ft. (1,829 mm) o.c. max or per design Moisture barrier

Cut concrete masonry units to match slope. Beam height varies, 4 in. (102 mm) min. Notch webs 2 3 4 in. (70 mm) for reinforcement Continuous reinforcement, 1 No. 5 (M #16) or as required Mesh or other grout stop device for cells not reinforced Concrete masonry wall Vertical reinforcement, as required Grout, as required

A A

Cut masonry rake beam

7b—Section A-A, Cut Concrete Masonry Rake Beam With Ladder Type Overhang Figure 7—Gable End Wall Gable End Wall Overhangs Figure 7a shows a continuously reinforced cast-in-place concrete rake beam along the top of the gable end wall. The beam is formed over uncut block in courses successively shortened to match the slope of the roof. A minimum of 4 in. (102 mm) is needed from the highest projected corner of block to the top of the beam. Reinforcement that is continuous with the bond beam reinforcement in the side walls is placed in the top of the beam. In this detail, an outlooker type overhang is shown where the rake beam is constructed 31/2 in. (89 mm) lower than the trusses so that a pressure treated 2 x 4 (38 x 89 mm) can pass over it. A ladder type overhang detail also can be used with the concrete rake beam where the beam is

constructed to the same height as the trusses similar to that shown for the cut masonry rake beam in Figure 7b. Figure 7b shows a continuously reinforced cut masonry rake beam along the top of the gable end wall. Masonry units are cut to conform to the roof slope at the same height as the roof trusses. A 2 3/4 in. (70 mm) deep notch is cut into the tops of the concrete masonry webs to allow placement of reinforcement that is continuous with the bond beam reinforcement in the side walls. A minimum of height of 4 in. (102 mm) is needed for the cut masonry bond beam. In this figure, a ladder type overhang is shown. However, an outlooker type overhang detail can be used similar to that shown for the cast-in-place concrete rake beam in Figure 7a. 172

REFERENCES 1. Building Code Requirements for Masonry Structures, ACI 530-02/ASCE 5-02/TMS 402-02. Reported by the Masonry Standards Joint Committee, 2002. 2. The Guide to Concrete Masonry Residential Construction in High Wind Areas. Florida Concrete & Products Association, Inc., 1997. 3. Standard for Hurricane Resistant Residential Construction, SSTD 10-99. Southern Building Code Congress International, Inc., 1999. 4. 2000 International Building Code. International Code Council, 2000. 5. Steel Reinforcement for Concrete Masonry, TEK 12-4C. National Concrete Masonry Association, 2002. 6. Annotated Design and Construction Details for Concrete Masonry, TR 90B. National Concrete Masonry Association, 2003. 7. Design for Dry Single-Wythe Concrete Masonry Walls, TEK 19-2A. National Concrete Masonry Association, 2002. 8. Flashing Strategies for Concrete Masonry Walls, TEK 19-4A. National Concrete Masonry Association, 2003. 9. Flashing Details for Concrete Masonry Walls, TEK 19-5A. National Concrete Masonry Association, 2003. 10.Minimum Design Loads for Buildings and Other Structures , ASCE 7-02. American Society of Civil Engineers, 2002.

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MODULAR LAYOUT OF CONCRETE MASONRY Keywords: construction, construction details, dimensions, metric, modular coordination, wall openings

TEK 5-12 Details

(2008)

(203 mm) vertically and horizontally, but may also include 4in. (102 mm) modules for some applications. These modules provide overall design flexibility and coordination with other building products such as windows, doors, and other similar elements as shown in Figures 1 and 2.

INTRODUCTION Although concrete masonry structures can be constructed using virtually any layout dimension, for maximum construction efficiency and economy, concrete masonry elements should be designed and constructed with modular coordination in mind. Modular coordination is the practice of laying out and dimensioning structures and elements to standard lengths and heights to accommodate modular-sized building materials. When modular coordination is not considered during the design phase, jobsite decisions must be made—often in haste and at a cost. This TEK provides recommendations for planning masonry construction to minimize cutting of masonry units or using nonstandard unit sizes. When a project does require non-modular layout, further design and construction issues need to be addressed, including: Placement of vertical reinforcement—In construction containing vertical reinforcing steel, the laying of units in other than running (half) bond or stack bond interrupts the vertical alignment of unit cells. As a result, reinforcement placement and adequate consolidation of grout becomes difficult, and partial grouting of walls is virtually impossible. Interruption of bond pattern—In addition to the aesthetic impact a change in bond pattern can create, building codes often contain different design assumptions for masonry constructed in running bond versus other bond patterns. Walls incorporating more than a single bond pattern may present a unique design situation. Locating control joints—In running bond, control joint construction can be accomplished using only full and halfsize units. Similarly, stack bond construction only requires full-size units when control joints are properly spaced and detailed. However, with other bond patterns units may need to be cut if specially dimensioned units are not used or are not available. Modular Wall Elevations Standard concrete masonry modules are typically 8 in. TEK 5-12 © 2008 National Concrete Masonry Association

Modular Wall Openings The rough opening dimensions illustrated in Figure 1 apply to the layout and construction of the masonry. To allow for fastening windows and doors to the masonry, however, the nominal heights and widths of these elements are slightly less. For conventional construction methods, the widths of masonry openings for doors and windows should generally be 4 in. (102 mm) larger than the door or window width. This allows for 2 in. (51 mm) on each side of the opening for framing. The heights of masonry openings to accommodate windows are typically 8 in. (203 mm) greater than the window height. This opening size allows for 2 in. (51 mm) above and below for framing and 4 in. (102 mm) for installation of a sill at the bottom of the window. Masonry openings for doors are commonly either 2 or 4 in. (51 or 102 mm) greater than the door height, allowing for the door framing as well as the use of a standard-sized door. Thus, door and window widths of 28, 36, 44, and 52 in. (711, 914, 1,118 and 1,321 mm) (and so on in 8 in. (203 mm) increments) do not require the masonry to be cut. Modular window heights are any multiple of 8 in. (203 mm), with a masonry window opening 8 in. (203 mm) greater than the height of the window if a 4-in. (102 mm) sill will be used. Similarly, door heights 2 in. (51 mm) less than any even multiple of eight can be installed without the need for cutting the masonry. For the commonly available 84-in. (2,134 mm) high door, a 4-in. (102 mm) door buck can be placed at the top of the opening. In addition, precast lintels are available in some areas containing a 2 in. (51 mm) notch to accommodate 80-in. (2,032 mm) doors. Hollow metal frames for doors should be ordered and delivered for the masonry before the other door frames in the project are scheduled for delivery. For economy, the frames should be set before the walls are built. If the walls are built before the frames are set, additional costs are incurred to set special knock down door frames and attachments. 174

Not Recommended Construction: Utilizing non-modular layouts or openings results in unnecessary cutting of the masonry units (shown here as shaded). The end product is more difficult to construct, produces more waste, and is more costly compared to a similar structure employing a modular layout. A d d i t i o n a l l y, p l a c i n g a n d consolidating grout in the reduced-size cores of the field-cut units may prove difficult.

52 in. (1,321 mm) 116 in. (2,946 mm) 84 in. (2,134 mm) 44 in. (1,118 mm)

36 in. (914 mm)

40 in. (1,016 mm)

24 in. (610 mm)

40 in. (1,016 mm)

12 in. (305 mm)

= Nonstandard or field-cut units

In this example, it is obvious the aesthetic impact non-modular layouts have on the final appearance of a structure. Not so obvious is the additional cost of construction. To further illustrate this concept, consider the following comparison of the modular and non-modular layouts shown here: Total area of non-modular layout = 122.4 ft2 (11.38 m2); 84.7 ft2 (7.87 m2) net Total area of modular layout = 126.7 ft2 (11.77 m2); 88.9 ft2 (8.26 m2) net Number of units used in non-modular layout = 122 Number of units used in modular layout = 110

Recommended Construction: The wall elevation shown here reduces the need to cut units by utilizing modular openings and opening locations (i.e., each dimension shown is evenly divisible by 8 in. (203 mm). By coordinating opening sizes and locations, the cells of hollow masonry 48 in. units align (which facilitates the (1,219 mm) placement of vertical reinforcement and consolidation of grout), labor time is reduced and materials are not wasted.

48 in. (1,219 mm) 120 in. (3,048 mm) 88 in. (2,235 mm)

32 in. (813 mm)

40 in. (1,016 mm)

24 in. (610 mm)

40 in. (1,016 mm)

16 in. (406 mm)

Figure 1— Modular Wall Elevations Modular Wall Sections For door and window openings, the module size for bond patterns and layout are nominal dimensions. Actual dimensions of concrete masonry units are typically 3/8 in. (9.5 mm) less than nominal dimensions, so that the 4 or 8-in. (102 or 203 mm) module is maintained with 3/8 in. (9.5 mm) mortar joints. Where mortar joint thicknesses differ from 3/8 in. (9.5 mm) (as may be specified for aesthetic purposes or with brick construction), special consideration is required to

maintain modular design. Figure 3 illustrates this concept. Typically, concrete masonry units have nominal face dimensions of (height by length) 8 by 16 in. (203 by 406 mm), and are available in nominal widths ranging from 4 in. to 16 in. (102 to 406 mm) in 2-in. (51 mm) increments. In addition to these standard sizes, other unit widths, heights and lengths may be available from concrete masonry producers. The designer should always check local availability of specialty units prior to design. 175

Masonry Opening Width = Window Opening Width + 4 in. (102 mm)

2 in. (51 mm) Framing

2 in. (51 mm) Framing 2 in. (51 mm) Framing

Masonry Opening Height = Window Opening Height + 8 in. (203 mm)

Masonry Opening Width = Door Opening Width + 4 in. (102 mm)


4 in. (102 mm) Sill Height


Masonry Opening Height = Door Opening Height + 2 in. (51 mm)

Window Openings

2 in. (51 mm) Framing 2 in. (51 mm) Framing

Door Openings

Figure 2—Modular Wall Openings

8 in. (203 mm)

8 in. 7 7 8 in. (203 mm) (197 mm)

Wall tie 5

8 in. (203 mm)

Wall tie 3

in. (11 mm)

8 in. (9.5 mm)

12

2 1 4 in. (57 mm)

2 1 4 in. (57 mm)

Recommended Construction: · Vertical coursing of bed joints of each wythe align. · Appropriate joint thickness selected.

Not Recommended Construction: · Misalignment of bed joints makes installation of wall ties difficult and reduces their effectiveness in transferring loads. · Inappropriate joint thickness selected. · May be partially compensated for by the use of adjustable wall ties, 11/4 in. (32 mm) max. misalignment (refs. 1, 2, 3)

Figure 3—Modular Wall Sections 176

Incorporating brick into a project, either as a structural component or as a veneer, can present unique modular coordination considerations in addition to those present with single wythe construction. Brick most commonly have a nominal width of 4 in. (102 mm), length varying from 8 to 16 in. (203 to 406 mm) and height from 2 1/2 to 6 in. (64 to 152 mm). The specified dimensions of modular concrete and clay brick are typically 3 5/8 by 2 1/4 by 7 5/8 in. (92 by 57 by 194 mm), but may be available in a wide range of dimensions. Because of their unique dimensions, concrete and clay brick are usually laid with bed joints that are slightly larger (or sometimes smaller depending upon the actual size of the brick) than the standard 3/8 in. (9.5 mm) mortar joint thickness. For example, common modular brick are laid with a 5/12 in. (11 mm) thick bed joint, thereby providing a constructed height of 2 2/3 in. (68 mm) for one brick and one mortar joint. (Note that a 5/12 in. (11 mm) thick bed joint is within allowable mortar joint tolerances (refs. 1, 2).) The result is that three courses of brick (including the mortar joints) equals one 8-in. (203 mm) high module, thereby maintaining modular coordination (see Figure 3). Modular Building Layouts and Horizontal Coursing In addition to wall elevations, sections and openings, the overall plan dimensions of a structure also need to be considered, especially when using units having nominal widths other than 8 in. (203 mm). Ideally, the nominal plan dimensions of masonry structures

should be evenly divisible by 8 in. (203 mm). This allows constructing each course of a wall using only full-length or half-length units, which in turn reduces labor and material costs. In addition, maintaining an 8-in. (203 mm) module over the length of a wall facilitates the turning of corners, whereby half of the units from one wall interlock with half of the units from the intersecting wall. As an alternative to cutting units or changing building dimensions, corner block can be used if available. These units are specifically manufactured to turn corners without interrupting bond patterns. Concrete Masonry Corner Details, TEK 5-9A (ref. 4) contains a variety of alternatives for efficiently constructing corners. Metric Coordination One additional consideration for some projects is the use of standard sized (inch-pound) masonry units in a metric project. Similar to inch-pound units, masonry units produced to metric dimensions are 10 mm (13/32 in.) less than the nominal dimensions to provide for the mortar joints. Thus, the nominal metric equivalent of an 8 by 8 by 16 in. unit is 200 by 200 by 400 mm (190 by 190 by 390 mm net unit dimensions). Since inch-pound dimensioned concrete masonry units are approximately 2% larger than hard metric units, complications can arise if they are incorporated into a structure designed on a 100 mm (3.9 in.) metric module, or vice versa. Metric Design Guide for Concrete Masonry Construction and TEK 3-10A, Metric Concrete Masonry Construction (refs. 5, 6) provide detailed guidance for incorporating soft metric units (standard inch-pound units) into a hard metric design project.

REFERENCES 1. International Building Code. International Code Council, 2003 and 2006. 2. Specification for Masonry Structures, ACI 530.1-05/ASCE 6-05/TMS 602-05. Reported by the Masonry Standards Joint Committee, 2005. 3. Building Code Requirements for Masonry Structures, ACI 530-05/ASCE 5-05/TMS 402-05. Reported by the Masonry Standards Joint Committee, 2005. 4. Concrete Masonry Corner Details, TEK 5-9A. National Concrete Masonry Association, 2004. 5. Metric Design Guide for Concrete Masonry Construction, TR-172. National Concrete Masonry Association, 2000. 6. Metric Concrete Masonry Construction, TEK 3-10A. National Concrete Masonry Association, 2008.

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ROLLING DOOR DETAILS FOR CONCRETE MASONRY CONSTRUCTION

TEK 5-13 Details

(2007)

Keywords: construction details, door jambs, fasteners, fire resistance, lateral loads, reinforcement, wall openings, wind loads INTRODUCTION Openings in concrete masonry walls utilize lintels and beams to carry loads above the openings. When openings incorporate rolling doors (also referred to as overhead coiling doors or coiling doors), wind loads on the door are transferred to the surrounding masonry through the door guides and fasteners. In some instances, the rolling doors have been designed for specific wind load applications, and are heavily dependent on the structural integrity of the door jamb members as they are attached to building walls at jamb locations. This TEK discusses the forces imposed on a surrounding concrete masonry wall by rolling doors, and includes recommended details for jamb construction. Lintel design, to carry the loads imposed on the top of the opening, are covered in Allowable Stress Design of Concrete Masonry Lintels and Precast Concrete Lintels for Concrete Masonry Construction (refs. 1, 2). LOADS EXERTED BY ROLLING DOORS Architects and building designers should determine the loads that rolling doors exert on the wall around the opening. Dead loads include the weight of the door curtain, counterbalance, hood, operator, etc., that is supported by the wall above the opening. Live loads result from wind that acts on the door curtain. Rolling doors are available with windlocks, which prevent the door curtain from leaving the guides due to wind loading. On doors without windlocks, the only wind load force that the curtain exerts on the guides is normal to the opening. For doors with windlocks, there is an additional load parallel to the opening (see Figures 1 and 2 for facemounted and jamb-mounted doors, respectively). This load is the catenary tension that results when the curtain deflects sufficiently to allow the windlocks to engage the windbar in the guide. This force acts to pull the guides toward the center of the opening. The door is exposed to a additive wind loads, from both inside and outside the building. Calculating the parallel force involves several variables, the most prominent of which are the width of the opening and

the design wind load. It is also important to note that the door must withstand both positive and negative wind loads. Including these forces in the design of the jamb and its supporting structure can help prevent a jamb failure and allow the building to fully withstand its specified wind load requirements. The rolling door manufacturer can provide a guide data sheet for quantifying the loads imposed by the overhead coiling doors due to the design wind load. The following conditions need to be considered: • The wall above the door opening must be designed to support the total hanging dead load. The face of wall-mounted doors may extend above the opening for 12 to 30 in. (305-762 mm). The door guide wall angles must be mounted to the wall above the opening to support the door. When the door has a hood to cover the coiled door and counter-balance, some provision must be made to fasten the top of the hood and hood supports to the masonry wall. See also Fasteners for Concrete Masonry (ref.3). • Reinforcement in jambs is recommended to adequately distribute the forces imposed by the door. • Reinforcement locations should be planned such that the reinforcement does not interfere with expansion anchor placement. ACCOMMODATING MASONRY REINFORCEMENT AND DOOR FASTENERS Rolling door contractors and installers sometimes encounter reinforcement in walls at locations where door jamb fasteners have been specified. Arbitrarily changing either the reinforcement location or the fastener location is not recommended, as either can negatively impact performance. Changing the door manufacturer's recommended jamb fastener locations may reduce the structural performance of the rolling door or possibly void the fire rating. The typical masonry jamb detail shown in Figure 3 indicates recommended vertical reinforcement locations 178


for concrete masonry jambs to provide an area for the door fasteners. The detail shows a “reinforcement-free zone” to allow for fasteners of either face-mounted or jamb-mounted rolling doors. The Door and Access Systems Manufacturers Association International (DASMA) recommends that vertical reinforcement should be within 2 in. (51 mm) of either corner of the wall at the jamb (ref. 4). Existing Construction Before installing fasteners in existing masonry construction, the following steps should be followed to locate the reinforcement, to avoid interference: • If structural drawings are available, the project engineer should review the drawings to determine whether or not the jamb reinforcement locations conflict with the specified door jamb fastener locations. • If the building’s structural plans are not available, either drill representative “pilot holes” or use a device similar to an electronic stud locator to determine the steel reinforcement locations. Once the steel reinforcement has been located, if it is concluded that the reinforcement will interfere with installing jamb fasteners, DASMA recommends that one of the following courses of action be taken: 1. Consider an alternate door jamb mounting or door size to assure that the reinforcement will not interfere with jamb fasteners.

C

B

Force F1

A Force F3

2. If an alternate door jamb mounting or alternate door size cannot be accomplished, consult a structural engineer to determine a workable solution. One possible solution is to contact the door manufacturer to obtain an alternate conforming hole pattern for the mounting, which would not interfere with the existing reinforcement. Another solution may be to bolt a steel angle to the concrete masonry jambs, which allows the door guides to then be welded or bolted to the steel angle. FIRE-RATED ROLLING DOOR CONNECTIONS When installed in a fire-rated concrete masonry wall, rolling steel fire doors must meet the code-required fire rating corresponding to the fire rating of the surrounding wall. For fire testing, the doors are mounted on the jambs of a concrete masonry wall intended to replicate field construction. The fire door guides must remain securely fastened to the jambs and no “through gaps” may occur in the door assembly during the test. Figure 4 shows a representative jamb construction and guide attachment details for a four-hour fire rated assembly. Note that guide configurations and approved jamb construction will vary with individual fire door manufacturer's listings. Consult with individual manufacturers for specific guide details and approved jamb constructions.

Force F5 Door opening

Door opening

B

Load Direction 1 Curtain

Force F2

Force F3 Load Direction 1 Curtain

Force F2

C Force F1

Load Direction 2

Force F4

(a) Without windlock C

B

A Force F2

(a) Without windlock Force F5

Door opening Force F1

Windbar

Load Direction 2

Load Direction 1 Curtain

Force F3 Windlock

Load Direction 2

(b) With windlock Figure 1—Imposed Forces for Face-Mounted Doors (ref. 5)

Door opening

Force F3 B C Force F1

Force F2 Windlock Force F4

Windbar Load Direction 1 Curtain

Load Direction 2

(b) With windlock Figure 2—Imposed Forces for Jamb-Mounted Doors (ref. 5) 179

2 in. (51 mm) A max. clearance Vertical reinforcement

Grout-filled cell

Alternate jamb-mounted door

Thickness varies

2 in. (51 mm) A max. clearance Face-mounted door

A

Note that a minimum amount of masonry cover over reinforcing bars is required (refs. 6, 7) to protect against steel corrosion. For masonry exposed to weather or earth, this minimum cover is 11/2 in. (38 mm) for No. 5 (M#16) bars and smaller, and 2 in. (51 mm) for bars larger than No. 5 (M#16). However, DASMA recommends a maximum distance of 2 in. (51 mm) from the face of the masonry to the reinforcing bar (ref. 4) in order to provide the largest possible clear area for fastener installation. See Steel Reinforcement for Concrete Masonry (ref. 9) for more detailed information on placing reinforcement in concrete masonry. Figure 3—Typical Masonry Jamb Detail for Face-Mounted and Alternate Jamb-Mounted Rolling Doors (ref. 4) 2 in. (51 mm) A max. clearance

Vertical reinforcement Grout-filled cell

A

2 in. (51 mm) max. clearance

2 in. (51 mm) A max. clearance

A Note that a minimum amount of masonry cover over reinforcing bars is required (refs. 6, 7) to protect against steel corrosion. For masonry exposed to weather or earth, this minimum cover is 11/2 in. (38 mm) for No. 5 (M#16) bars and smaller, and 2 in. (51 mm) for bars larger than No. 5 (M#16). However, DASMA recommends a maximum distance of 2 in. (51 mm) from the face of the masonry to the reinforcing bar (ref. 4) in order to provide the largest possible clear area for fastener installation. See Steel Reinforcement for Concrete Masonry (ref. 9) for more detailed information on placing reinforcement in concrete masonry. B

Note: Underwriters Laboratories has approved the welded guide details ONLY AS SHOWN. FM Approvals (Factory Mutual) does not allow guides to be welded to steel jambs. Figure 4—Approved Jamb Construction for Maximum 4-Hour Fire Rating (ref. 8)B 180

REFERENCES 1. Allowable Stress Design of Concrete Masonry Lintels, TEK 17-1B. National Concrete Masonry Association, 2001. 2. Precast Concrete Lintels for Concrete Masonry Construction, TEK 17-2A. National Concrete Masonry Association, 2000. 3. Fasteners for Concrete Masonry, TEK 12-5. National Concrete Masonry Association, 2005. 4. Metal Coiling Type Door Jamb Construction: Steel Reinforcement In Masonry Walls, TDS-259. Door and Access Systems Manufacturers Association International, 2005. 5. Architects and Designers Should Understand Loads Exerted By Overhead Coiling Doors, TDS-251. Door and Access Systems Manufacturers Association International, 2005. 6. International Building Code 2003. International Code Council, 2003. 7. International Building Code 2006. International Code Council, 2006. 8. Common Jamb Construction for Rolling Steel Fire Doors: Masonry Construction—Bolted and Welded Guides, TDS-261. Door and Access Systems Manufacturers Association International, 2005. 9. Steel Reinforcement for Concrete Masonry, TEK 12-4D. National Concrete Masonry Association, 2006.

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CONCRETE MASONRY HURRICANE AND TORNADO SHELTERS Keywords: construction details, high winds, hurricane, impact, reinforced masonry, storm shelters, testing, tornado INTRODUCTION Extreme windstorms, such as hurricanes and tornadoes, can pose a serious threat to buildings and their occupants in many parts of the country. Hurricanes and tornadoes produce wind pressures and generate flying debris at much higher levels than those used to design most commercial and residential buildings. Hence, these storms require residents to either evacuate the area or seek protection in dedicated shelters. Storm shelters are buildings, or parts of buildings, that are designed and built specifically to provide a highly protected space where community members or occupants can seek refuge during these events. The newly-developed standard ICC-500, Standard on the Design and Construction of Storm Shelters (ref. 1), provides design and construction requirements for hurricane and tornado shelters. The standard covers structural design requirements for these shelters, as well as requirements for ventilation, lighting, sanitation, egress and fire safety. ICC-500 covers both hurricane and tornado shelters, and includes requirements for two types of shelters: community shelters, buildings specifically dedicated to provide shelter during a storm; and residential shelters, which are typically reinforced rooms within a home, where the occupants can safely seek refuge during a hurricane or tornado. Prior to the publication of ICC-500, builders and homeowners seeking storm shelter guidance have used the FEMA 320 publication Taking Shelter From the Storm: Building a Safe Room Inside Your House, the FEMA 361 publication Design and Construction Guidance for Community Shelters, and the NCMA publication Concrete Masonry Tornado Safe Rooms (refs. 2, 3, 6). Research performed at the Texas Tech University Wind Science and Engineering Research Center (ref. 4), however, found that the FEMA recommendations were overly conservative for concrete masonry for impact resistance. Concrete masonry walls have been tested to withstand the ICC-500 criteria, resulting in more economical wall designs than those previously recommended by FEMA. TEK 5-11, Residential Details for High-Wind Areas (ref.

TEK 5-14 Details (2008)

5), provides prescriptive requirements for reinforced concrete masonry homes in hurricane-prone areas, based primarily on providing a continuous load path from roof to foundation. These are general residential details, and do not address storm shelters. In contrast, the requirements described in this TEK apply only to dedicated shelters, or to shelter areas within a home, meant to provide temporary protection during a storm. Concrete masonry walls capable of meeting the ICC-500 requirements are presented, as well as the results of impact testing on concrete masonry walls. Note that this TEK does not address all requirements of ICC-500. ICC-500 WIND DESIGN CRITERIA FOR SAFE ROOM WALLS AND FLOORS General design considerations for storm shelters include: • adequate wall and roof anchorage to resist overturning and uplift, • walls and ceiling, as well as openings such as doors and windows, must withstand design wind pressures and resist penetration by windborne objects and falling debris, and • connections between building elements must be strong enough to resist the design wind loads. Figure 2 shows a typical detail for connecting a concrete roof slab to concrete masonry shelter walls, using reinforcing bars to provide adequate load transfer. ICC-500 defines design tornado wind speeds across the United States, and hurricane design wind speeds for applicable coastal areas. When the shelter is to provide shelter from both hurricanes and tornadoes, the most restrictive of the two design criteria should be used for design. The reader is referred to the standard (ref. 1) for maps defining these speeds. Note that wind speeds in ICC-500 are much higher than wind speeds in ASCE-7 (ref. 7) or the International Building Code (refs. 8, 9), and are considered to provide the maximum or ultimate tornado or hurricane design wind speed at a site. Therefore, the wind load contribution in the load combinations is adjusted accordingly. For example, 1.0W rather than 1.6 W is used as the factored wind load in strength design combinations. In allowable stress design, 0.6W is used instead of W. Wind pressures are to be based on exposure C, although exposure B is permitted if it exists for all wind directions. 182


In addition to being designed for these design wind speeds, shelter walls and ceilings must be able to withstand impact from flying debris, whose projectile speed varies with the design wind speed. The ICC-500 design criteria vary with location. The concrete masonry walls tested at Texas Tech were tested at the most stringent of the ICC-500 wind speeds and impact requirements, as follows. For tornado shelters, the highest design wind speed prescribed by ICC-500 is 250 mph (402 km/h). Corresponding walls and ceilings must withstand impact from a 15 lb (6.8 kg) wooden 2 x 4, propelled at 100 mph (161 km/h) and 67 mph (108 km/h), respectively. These conditions will more than satisfy the less stringent requirements for hurricane shelters. For hurricane shelters, the highest design wind speed in ICC-500 is 237 mph (381 km/h) (with the exception of Guam, which has a design hurricane wind speed of 256 mph (412 km/h)). In addition, walls subject to this 237 mph (381 km/h) design wind speed must be capable of withstanding impact from a 9 lb (4.1 kg) wooden 2 x 4 propelled at 100 mph (161 km/h). Ceilings and other horizontal surfaces must withstand impact from the same projectile propelled a 25 mph (40 km/h). In addition to these requirements, ICC-500 defines requirements for tie-down to the foundation and adequate foundation sizing to resist the design overturning and uplift forces.

CONCRETE MASONRY ASSEMBLIES FOR STORM SHELTERS A typical concrete masonry storm shelter design is shown in Figure 1. Several concrete masonry systems have been successfully tested to withstand the 15 lb (6.8 kg) 2 x 4 propelled at 100 mph (161 km/h) (ref. 4). Solidly grouted 8-in. (203-mm) concrete masonry walls with No. 5 (M #16) reinforcement at 48 in. (1,219 mm) o.c., with one horizontal No. 5 (M#16) min. at the top of the wall and in the footing or bottom of the wall, can withstand these conditions. All weight classes of concrete masonry meet the strength and impactresistance requirements. The engineer will use the masonry weight in the shelter design to resist overturning. Regardless of the concrete masonry density, the weight of the grouted masonry assembly provides increased overturning resistance compared to low-mass systems. Although solidly grouted 6-in. (152-mm) concrete masonry walls with No. 4 (M #13) bars at 32 in. (813 mm) o.c. successfully passed the impact test, they may not have enough weight to resist overturning for the most severe tornado loading, based on a 250 mph (402 km/h) wind speed. Hence, the details included in this TEK show 8-in. (203-mm) storm shelter walls. Solidly grouted 6-in. (152-mm) walls may be adequate for lower wind requirements, however. A ceiling system using 7-in. (178-mm) deep bottom chord bearing steel joists infilled with concrete masonry units and Impact rated door max. size 3 ft (914 mm) (door may swing in or out) Tee anchorage four per jamb

6ft to 8 ft (1.83 to 2.44 m) is optimum for stability

6 ft to 8 ft (1.83 to 2.44 m) is optimum for stability

1 ft 6 in. (457 mm)

No. 5 (M #16) vertical reinforcement at 48 in. (1,219 mm) o.c., max.

3 ft (914 mm)

Grout solid (typ.) Reinforced lintel above door w/one No. 5 (M #16)

16 ga. metal door frame

8 in. (203 mm) CMU, min.

Grout all cells solid

Note: The total height of the shelter (from the top of the floor slab to the top of the ceiling slab) should not exceed 8 ft (2.44 m) to reduce vulnerability to overturning. Figure 1—Plan View of Typical Concrete Masonry Storm Shelter 183

grout to a nominal 8-in. (203-mm) depth was also tested and found to withstand the 15 lb (6.8 kg) 2 x 4 at 67 mph (108 km/h) protocol (ref. 4). No. 4 (M #13) reinforcing bars were placed perpendicular to the joists, at 8 in. (203 mm) o.c. Note that all assemblies were successfully tested using standard masonry grout per ASTM C 476 (ref. 10). Some previous references recommend the use of concrete to fill the masonry cores, rather than grout, but this is contrary to the building code and is highly discouraged. RESIDENTIAL SHELTERS The purpose of an in-home shelter is to provide an area where the occupants can safely shelter during a high wind event. In flood prone areas, the shelter must not be built where it can be flooded. The shelter should be accessible from all areas of the house and should be free of clutter to provide immediate shelter. If not within the residence, the shelter needs to be within 150 ft (45.72 m) of the residence (ref. 1). FEMA (ref. 2) suggests a basement, an interior room on the first floor on a foundation extending to the ground or on top of a concrete slab-on-grade foundation or garage floor as good locations for an in-home shelter. Below-ground safe rooms provide the greatest protection, as long as they are designed to remain dry during the heavy rains that often accompany severe windstorms. When shelters are located below grade, the soil surrounding the walls can be considered as protection from flying debris during a high wind event, as long as the wall is completely below grade and soil extends at least 3 ft (914 mm) away from the wall, with a slope no greater than two inches per foot (167 mm/m) for that 3 ft (914 mm) distance. When these conditions are met, the walls do not need to meet the missile impact requirements described above. Below-grade ceilings must have a minimum of 12-in. (305-mm) of soil cover to be exempt from the impact testing requirements. Sections of either interior or exterior residence walls that are used as walls of the safe room must be separated from the structure of the residence so that failure of the residence, which is designed for a much lower loading, will not result in a failure of the safe room. Residential Retrofit Special consideration must be given when retrofitting a shelter into an existing home. Figures 3 through 5 illustrate typical details for connecting shelter elements to an existing basement wall. The results of recent testing (ref. 4) has improved the economy of constructing retrofits. Previously, a concrete masonry storm shelter would have required a large dedicated foundation. Research confirms, however, that considering the weight of fully grouted concrete masonry, a large foundation is not required to adequately resist the uplift and overturning forces. Accordingly, ICC-500 allows concrete masonry storm shelters to be constructed within one and two family dwellings on existing slabs on grade without a dedicated foundation, under the following conditions: • the calculated soil pressure under the slab supporting the

Do not attach shelter ceiling to floor or ceiling above

4 in. (102 mm)

No. 4 (M #13) bar at 16 in. (406 mm) o.c. min. Concrete ceiling No.4 (M #13) bar at 16 in. (406 mm) o.c. each way, min. 8 in. (203 mm) CMU wall, solid grouted with one No. 5 (M #16) at 48 in. (1,219 mm) o.c. min.

Two No. 4 (M #13) or one No. 5 (M #16) continuous in bond beam

Figure 2—Typical Shelter Wall/Ceiling Connection

Existing reinforced 8 in. (203 mm) masonry basement wall, min. with soil the full height of the shelter

New masonry shelter walls (see Figures 4 and 5)

Figure 3—Retrofit Shelter: Plan View

No. 4 (M #13) reinforcing bar epoxied into floor slab at all corners and each side of doorway, min.

31 2 in. (89 mm) min. thickness existing slab-on-grade w/ 6 x 6 W1.1 x W1.4 A WWF, min.

CL

8 in. (203 mm) solid grouted CMU min. with 4 in. (102 mm) cast-in-place roof.

Splice per code

A

This slab reinforcement is not required when the slab dead load is not required to resist overturning. Figure 4—Retrofit Shelter: Direct-Dowel to Existing Slab 184

storm shelter walls does not exceed 2,000 psf (95.8 kPa) for design loads other than the design storm events and 3,000 psf (143.6 kPa) for design storm shelter events, • at a minimum, the storm shelter is anchored to the slab at each corner of the structure and on each side of the doorway opening (see Figure 4), and • the ICC-500 slab reinforcement requirements are waived if the slab dead load is not required to resist overturning.

Epoxy No. 4 (M #13) dowel at 16 in. (406 mm) o.c., min.

Existing reinforced 8 in. (203 mm) masonry wall

COMMUNITY SHELTERS Requirements for community shelters are similar to those for residential, but require a larger area and additional features in anticipation of sheltering more people. For example, community storm shelters require: signage to direct occupants to storm shelter areas; wall, floor and ceiling assemblies with a minimum 2-hour fire resistance rating; as well as additional ventilation and sanitation facilities.

Development length Figure 5—Retrofit Shelter: New Wall/Existing Wall Connection

REFERENCES 1. Standard on the Design and Construction of Storm Shelters, ICC-500. International Code Council and National Storm Shelter Association, 2008. 2. Taking Shelter From the Storm: Building a Safe Room Inside Your House, FEMA 320. Federal Emergency Management Agency, 2004. 3. Design and Construction Guidance for Community Shelters, FEMA 361. Federal Emergency Management Agency, 2000. 4. Investigation of Wind Projectile Resistance of Concrete Masonry Walls and Ceiling Panels with Wide Spaced reinforcement for Above Ground Shelters, NCMA Publication MR 21. Texas Tech University Wind Science and Engineering Research Center, 2003. 5. Residential Details for High-Wind Areas, TEK 5-11. National Concrete Masonry Association, 2003. 6. Concrete Masonry Tornado Safe Rooms, TR 200. National Concrete Masonry Association, 2002. 7. Minimum Design Loads for Buildings and Other Structures, ASCE 7-02 and ASCE 7-05. American Society of Civil Engineers, 2002 and 2005. 8. 2003 International Building Code. International Code Council, 2003. 9. 2006 International Building Code. International Code Council, 2006. 10. Standard Specification for Grout for Masonry, ASTM C 476-07. ASTM International, Inc., 2007.

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DETAILS FOR HALF-HIGH CONCRETE MASONRY UNITS INTRODUCTION Concrete masonry offers numerous functional advantages, such as structural load bearing, life and property protection, durability and low maintenance. Half-high concrete masonry units offer the additional advantages of a veneer-like appearance in economical single wythe construction. As for all concrete masonry units, integrally colored half-high brick-like units provide enduring strength and lasting resistance to fire and wind while maintaining a virtually maintenance-free façade. These attributes are appealing for both new construction and renovations in historic districts. Many designers are turning to half-high masonry because of its economy. As an alternative to a traditional cavity wall, these walls offer the same finished appearance, exterior durability and low maintenance coupled with a shorter construction time because of the single wythe loadbearing design. This TEK describes the use of half-high units for single wythe masonry construction. For veneer applications, see Refs. 1 and 2. HALF-HIGH UNITS Half-high concrete masonry units are produced to the same quality standards as other concrete masonry units. ASTM C 90 (ref. 3) governs physical requirements such as minimum compressive strength, minimum face shell and web thicknesses, finish and appearance, and dimensional tolerances. Like other concrete masonry units, half-highs are produced in a variety of sizes, unit configurations, colors and surface textures. In addition, special shapes, such as corners and bond beam units are also available. WALL PERFORMANCE Structural design considerations for half-high construction are virtually the same as those for conventional concrete masonry units. One aspect that may be different for half-high units is the unit strength. Typical nonarchitectural concrete masonry units have a minimum unit strength of 1,900 psi (13.10 MPa), corresponding to a specified compressive strength of masonry, f'm, of 1,500 psi (10.34 MPa). Half-high and other architectural units, however, are typically manufactured to a higher unit strength. Designers should check with producers about the strength of locally available

Related TEK: 3-8A, 5-7A, 19-2A NCMA TEK 5-15

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TEK 5-15

Details (2010)

units, with the intent of taking advantage of these higher strengths in their designs when available. Section properties for half-high units are essentially the same as for full-height units, and the same design aids can be used for both (see Ref. 4). In addition, because the core sizes are also typically the same as for full-height units of the same thickness, considerations for maximum reinforcing bar size as a percentage of the cell area are the same as well. See Ref. 5 for more detailed information. Because there are more horizontal mortar joints in a wall constructed using half-high units, there is slightly less concrete web area in the wall overall. Although this theoretically reduces the wall weight, in practice the wall weights of walls constructed using half-high units are within 1 psf (0.05 kPa) of those for full height units (see Ref. 6). To facilitate the construction of bond beams, half-high bond beam units are typically available with depressed webs to accommodate horizontal reinforcement. Grouting two half-high units provides an 8-in. (203-mm) deep bond beam, as shown in Figures 1 through 3. Note that the bottom unit of the bond beam should have depressed webs to accommodate the horizontal reinforcement, but the top unit need not have depressed webs.

Single Wythe Half-High Construction in Hartland, Wisconsin

Keywords: bond beam, construction details, flashing, reinforced concrete masonry, single wythe construction, water penetration resistance 1

186

Performance criteria for fire resistance , energy efficiency and acoustics of half-high units can be considered to be the same as for similar full height units. See Refs. 7 through 11 for further information. In addition, detailing window openings, door openings, etc., is the same as for single wythe masonry walls constructed using full-height units.

pocket in the masonry wall or by joist hangers, Figure 4 shows a unique application where half-high units have been corbelled out to provide bearing for a wood truss floor. This also provides continuous non-combustible bearing thickness without the need to stagger the joists. See Ref. 12 for additional floor and roof connection details. As for any single wythe construction, particular care should CONSTRUCTION be taken to prevent water from entering the building nterior. Dry Construction with half-highs is very similar to that for conwalls are attained when both the design and construction address ventional units. Some differences include: an increased number of water movement into, through and out of the wall. Considerations courses laid per wall height, greater amount of mortar needed, as include potential sources of water, unit and mortar characteristics, well as the difference in bond beam construction noted above. Crack crack control, workmanship, mortar joint tooling, flashing and control considerations are the same as for full height units. weeps, sealants, and water repellents. For single wythe masonry, As an alternative to supporting trusses by means of a an integral water repellent in both the units and mortar, as well as a compatible post-applied surface water repellent are Proprietary flashing and weep system recommended. See Refs. 13 -18 for more information. Reinforcement and grout, as required Figure 1 shows a proJoint reinforcement at 16 in. (406 mm) o.c. prietary flashing system that collects and directs water to Flashing and weeps in ungrouted the exterior of the wall and cores over bond beams out weep holes, without compromising the bond at mortar 8-in. (203-mm) high bond beam: joints in the face shells (see • two units high Ref. 15 for recommended • both courses fully grouted flashing locations). There • reinforcement, as required are a number of generic and • reduced webs for bottom unit: proprietary flashing, drain. 1 / 2 in 8 in. age, weep, mortar dropping 3 . 3 in control, and rain screen in. 2 3 in. systems available. Single 31/2 in. wythe flashing details using conventional flashing are Mesh or other grout stop included in Ref. 14. device Bearing plate detail* Solid grouted single Post-applied surface water wythe walls tend to be less repellent susceptible than ungrouted * Steel bar joists welded or bolted to bearing plate or partially grouted walls to moisture penetration, since Figure 1—Bearing Detail on Single Wythe Wall (ref. 19) 8-in. (203-mm) half-high unit* Strap anchor at 2 ft (610 mm) o.c. (for lateral support)

8-in. (203-mm) half-high unit* Strap anchor at 2 ft (610 mm) o.c. (for lateral support)

4-in. (102-mm) half-high unit* Through-wall flashing with stainless steel drip edge, weeps at 32 in. (813 mm) o.c. 10-in. (254-mm) half-high units* grouted to form bond beam Mesh or other grout stop device Reinforcement, as required Post-applied surface water repellent

Through-wall flashing with stainless steel drip edge, weeps at 32 in. (813 mm) o.c. 8-in. (203-mm) half-high units* grouted to form bond beam Mesh or other grout stop device Reinforcement, as required Post-applied surface water repellent

* integral water repellent in units & mortar Figure 2—Exterior Loadbearing Wall With Wood Truss Floor (ref. 19) 2

NCMA TEK 5-15

187

Flashing 2 in. (51 mm) high soap unit 2 in. (51 mm) concrete topping Precast planks 4-in. (102-mm) half-high units* Rigid insulation 8-in. (203-mm) halfhigh*

Bearing pad, min. 3 in. (76 mm) bearing "%!2).'0!$ v-)."%!2).'

Wallboard channel v$7#

Post-applied surface water repellent

Gypsumvwallboard $297!,, * integral water repellent in units & mortar

Exterior Nonloadbearing Wall Detail Precast Hollow Core Flooring Representative R-values*, with: 2 in. (51 mm) extruded polystyrene = R 13.2 h.ft2.oF/Btu (2.3 m2.K/W)

voids and cavities where moisture can collect are absent. As a result, solid grouted walls do not require flashing and weeps, although they do require other moisture control provisions, such as sealants and water repellents. For partially grouted walls, flashing should be placed in ungrouted cells. REFERENCES 1. Concrete Masonry Veneers, TEK 3-6B. National Concrete Masonry Association, 2005. 2. Crack Control for Concrete Brick and other Concrete Masonry Veneers, TEK 10-4. National Concrete Masonry Association, 2001. 3. Standard Specification for Loadbearing Concrete Masonry Units, ASTM C 9006b. ASTM International, Inc., 2006.

Flashing

2 in. (51 mm) high soap unit 2 in. (51 mm) concrete topping

2 in. (63 mm) polyisocyanurate = R 19.5 h.ft2.oF/Btu (3.4 m2.K/W) 21/2 in. (63 mm) polyisocyanurate = R 22.9 h.ft2.oF/Btu (4.0 m2.K/W)

10-in. (254-mm) precast planks 4-in. (102-mm) half-high units, integral water repellent in units and mortar 1 /2 in. (13 mm) rigid insulation Bearing pad, 3 in. (76 mm) min. bearing 5-v"%!2).' 1

1- /2 in. (38 mm) * Based on insulation 7# channel for R-values of 10, 14.4 ,%#2/5'(). electrical rough-in and 17.8, respectively (plus a reflective air Gypsum wallboard 297!,, space for the polyisocyanurate). Check with Rigid4(%2-!87)4( insulation with your manufacturer, joints taped, as required 34!0%$ as R-values may vary slightly. Post-applied surface

10-in. (254-mm) half-high units, grouted to form bond beam, integral water repellent in units and mortar Mesh or other grout stop device 8-in. (203-mm) half-high units, integral water repellent in units and mortar

/#/#534/- water repellent .293%!,%2 Vapor retarder, as required

Generic or proprietary throughwall flashing in ungrouted cells

Note that loadbearing corbels are required to be designed (ref. 20). Figure 3—Exterior Wall With Precast Hollow Core Plank Floor (ref. 19) NCMA TEK 5-15

3

188

12-in. (304-mm) half-high



6-in. (152-mm) CMU 11/2 in. (38 mm) channel for electrical rough-in Gypsum wallboard Note: loadbearing corbels are required to be designed (ref. 20).

Figure 4—Interior Bearing Wall With Top Chord Bearing Wood Truss Floor (ref. 19) REFERENCES (continued) 4. Section Properties of Concrete Masonry Walls, TEK 14-1B. National Concrete Masonry Association, 2007. 5. Steel Reinforcement for Concrete Masonry, TEK 12-4D. National Concrete Masonry Association, 2006. 6. Concrete Masonry Wall Weights, TEK 14-13B. National Concrete Masonry Association, 2008. 7. Fire Resistance Ratings of Concrete Masonry Assemblies, TEK 7-1C. National Concrete Masonry Association, 2009. 8. R-Values for Single Wythe Concrete Masonry Walls, TEK 6-2B. National Concrete Masonry Association, 2009. 9. Sound Transmission Class Ratings for Concrete Masonry Walls, TEK 13-1B. National Concrete Masonry Association, 2008. 10. Noise Control With Concrete Masonry, TEK 13-2A. National Concrete Masonry Association, 2007. 11. Outside-Inside Transmission Class of Concrete Masonry Walls, TEK 13-4. National Concrete Masonry Association, 2008. 12.Floor and Roof Connections to Concrete Masonry Walls, TEK 5-7A. National Concrete Masonry Association, 2001. 13.Water Repellents for Concrete Masonry Walls, TEK 19-1. National Concrete Masonry Association, 2006. 14. Design for Dry Single-Wythe Concrete Masonry Walls, TEK 19-2A. National Concrete Masonry Association, 2008. 15. Flashing Strategies for Concrete Masonry Walls, TEK 19-4A. National Concrete Masonry Association, 2008. 16. Flashing Details for Concrete Masonry Walls, TEK 19-5A. National Concrete Masonry Association, 2008. 17. Joint Sealants for Concrete Masonry Walls, TEK 19-6. National Concrete Masonry Association, 2008. 18. Characteristics of Concrete Masonry Units With Integral Water Repellents, TEK 19-7. National Concrete Masonry Association, 2008. 19. Intelligent Design, Half-High Architectural CMU. Illinois Concrete Products Association. 20. Building Code Requirements for Masonry Structures, ACI 530-08/ASCE 5-08/TMS 402-08. Reported by the Masonry Standards Joint Committee, 2008.



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AESTHETIC DESIGN WITH CONCRETE MASONRY INTRODUCTION One aspect of concrete masonry that has kept it at the forefront of building materials is its ability to incorporate and reflect a broad spectrum of existing architectural styles, as well as providing the designer with the ability to develop and present unique aesthetic affects and techniques. When skillfully designed, simple materials can provide unparalleled aesthetic enhancement. Inventive patterns, color choices (unit and mortar), unit sizes, and surface finishes (split face and standard) can be used in various concrete masonry bond patterns to evoke a sense of strength, modernity, tradition, or even whimsy. Within the confines of meeting applicable building codes and specifications, concrete masonry's modular sizes and range of colors, textures and patterns provide ample opportunity to demonstrate a design technique or overcome design challenges. In addition to the architectural finish, concrete masonry can provide the wall's structure, fire resistance, acoustic insulation, and energy envelope. This TEK addresses the proper application of architectural enhancements in concrete masonry wall systems. Where appropriate, related NCMA TEK and other documents are referenced to provide further information and detail.

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TEK 5-16

Details (2011)

These requirements assume an understanding of the techniques unique to the nature of masonry. The design and construction team should establish and consistently support ground rules affecting aesthetic interpretations of a project. It is also important for the client to realize the aesthetic standard that the project is based on, and that unusually high aesthetic standards can be more costly. In addition, certain high-profile areas, such as a building entrance, may require a custom level of quality, commensurate with an additional cost for the defined area. Several state and local masonry associations have developed guidelines for defining aesthetic requirements, and these can be a good resource for clarifying a project's aesthetic standards.

Communication With Clients Common dilemmas faced by designers are a client’s changing expectations and responses to the project’s changing appearance over time and under varying conditions. As discussed below, there are some basic requirements relative to aesthetics, but these are far from comprehensive. It is important to realize that code requirements primarily govern structural performance, not aesthetics. For example, code-required construction tolerances are designed to ensure that masonry units are placed such that the completed wall can act structurally as an integrated unit.

Related TEK:

1-1E, 2-3A, 3-8A, 5-2A, 5-12, 8-4A, 10-2C, 10-3, 10-4, 19-1 NCMA TEK 5-16

Figure 1—Use of Several Unit Colors to Complement the Site

Keywords: aesthetics, architectural masonry, architectural units, banding, concrete masonry units, control joints, modular coordination, sample panel 190 1

Sample panels are a good means to communicate the minimum contract-based aesthetic standard to all parties. The sample panel is typically constructed prior to the project, and in some cases a portion of the work can serve as the sample panel. The sample panel remains in place or at least available until the finished work has been accepted, since it serves as a comparison for the finished work. The sample panel should contain the full acceptable range of unit and mortar color, as well as the minimum expected level of workmanship. Cleaning procedures, as well as application of any coatings or sealants, should also be demonstrated on the sample panel. See TEK 8-4A, Cleaning Concrete Masonry, (ref. 1) for more information on cleaning. CONSIDERATIONS FOR CHOOSING CONCRETE MASONRY UNITS Architectural Concrete Masonry Units One of the most significant architectural benefits of designing with concrete masonry is its versatility—the finished appearance of a concrete masonry wall can be varied with the unit size and shape, color of units and mortar, bond pattern, and surface finish of the units. The term "architectural concrete masonry units” typically is used to describe units displaying any one of several surface finishes that affect the color or texture of the unit, allowing the structural wall and finished surface to be installed in a single step. TEK 2-3A, Architectural Concrete Masonry Units (ref. 2) provides an overview of some of the more common architectural units, although local manufacturers should be consulted for final unit selection. Architectural concrete masonry units are used for interior and exterior walls, partitions, terrace walls and other enclosures. Some units are available with the same treatment or pattern on both faces, to serve as both exterior and interior wall finish material, increasing both the economic and aesthetic advantages. Architectural units comply with the same performance-based quality standards as conventional concrete masonry, such as Standard Specification for Loadbearing Concrete Masonry Units, ASTM C90 (ref. 3). See Aesthetics in ASTM C90 (page 4) for more information. Concrete Masonry Unit Color Being produced from natural aggregates, concrete masonry has natural color variations from unit to unit. When a more monotone appearance is desired, there are various techniques that may be specified to increase the color uniformity in concrete masonry. Perhaps the best method is to specify the use of mineral pigments in the concrete mix, which are available in a wide range of colors. Pigments provide an integral color throughout the unit and minimize variations in color and texture found naturally in aggregate and sand deposits. Using several colors of integrally-colored concrete masonry units in the same 2

wall is an effective technique for producing other visual impacts, such as two-tone banding or complementary color palates (see Figure 1). Other methods are also used to improve color uniformity. One method is to specify the use of a post-applied stain, paint or coating on the units. With a paint or coating, the resulting film minimizes the texture of the masonry surface as well as the visual impact of the mortar joints. Paints and coatings for concrete masonry should be compatible with the masonry, and should in general allow for water vapor transmission. TEK 19-1, Water Repellents for Concrete Masonry Walls, (ref. 4) contains information on the applicability of different types of paints and coatings for concrete masonry walls. A more laborious method to improve color uniformity is to arrange with the masonry contractor for a presorting of on-site supplied block during certain stages of construction. Interaction With Sunlight Because it is produced from natural materials, concrete masonry walls often interact with changing sunlight in much the same way that natural stone does, appearing to change color as the light hits the wall at different angles. Figure 2 shows how even a conventional gray concrete masonry wall can interact with sunlight to present a range of color. This same attribute can be used to advantage with electric lighting, as well as on interior walls.

Figure 2—Effect of Changing Sunlight on Gray Concrete Masonry 191 NCMA TEK 5-16

Fluted concrete masonry units provide a rich texture and tend to enhance the sound attenuating properties of concrete masonry. The vertical flutes also provide an interesting interplay of light and shadow, which can be much more dramatic than smooth-faced units. MORTAR JOINTS While mortar generally comprises less than ten percent of a typical concrete masonry wall surface area, it can have a significant impact on the overall aesthetics of the completed structure. Mortar joint finishing, profiles and color can all impact the overall wall aesthetics. See also Concrete Masonry Handbook for Architects, Engineers, Builders (ref. 5) for information on mortar joints. Mortar Joint Tooling Tooling refers to finishing the mortar joints with a profiled tool that shapes and compacts the surface of the joint and provides a sharper, cleaner appearance for the wall. The surface shape of the tool determines the joint's profile (discussed in more detail in the following section). Tooling mortar joints also helps seal the outer surface of the joint to the adjacent masonry unit, improving the joint's weather resistance. For this reason, tooled joints that compact the mortar and do not create ledges to hold water are recommended for construction that will be exposed to weather. Mortar joints should be tooled when the mortar is thumbprint hard (a clear thumbprint can be pressed into

the mortar without leaving cement paste on the thumb). Tooling the joints before they reach this stage results in lighter colored joints, because more cement paste is brought to the surface of the joints. Joints tooled too early can also subsequently shrink away slightly from the adjacent concrete masonry unit. Tooling at the proper time allows this initial shrinkage to occur, then restores contact between the mortar and the unit producing a more weather-resistant joint. Conversely, later tooling can produce a darker joint. A consistent time of tooling will minimize variations in the final mortar color. For the cleanest result, horizontal mortar joints should be tooled before vertical joints. For white and light-colored mortar, Plexiglas jointers can be used to avoid staining the joints during tooling. After all joints are tooled, any mortar burrs on the wall should be trimmed off with a trowel or other tool (a tool such as a plastic loop is easier to use on a split face wall than a trowel, for example). As a final step the joints are dressed using a brush, a piece of burlap, or similar material.

Mortar Joint Profiles Traditional mortar joint profiles are illustrated in Figure 3. For walls not exposed to weather, the joint profile selection can be based on aesthetics and economics (as some joint profiles are more labor-intensive to produce). For exterior exposures, however, the mortar joint profile can impact the wall's weather resistance, as discussed above. Unless otherwise specified, mortar joints should be tooled to a concave profile when the mortar is thumbprint hard (refs. 6, 7). For walls exposed to weather, concave joints (Figure 3a) improve water penetration resistance by directing water away from the wall surface. In addition, because of the shape of the tool, the mortar is compacted against the concrete masonry unit to seal the joint. V-shaped joints 3a) Concave Joint (standard 3c) Grapevine Joint 3b) "V" Joint (Figure 3b) result in sharper shadow lines than unless otherwise specified) concave joints. Grapevine and weather joints (Figures 3c, 3d) provide a water-shedding profile, but do not result in the same surface compaction as concave or V-shaped joints. Both are used in interior walls to provide strong horizontal 3d) Weather Joint 3e) Beaded Joint 3f) Flush Joint lines. Beaded joints (Figure 3e) are formed by tooling the extruded mortar into a protruding bead shape. Care must be taken to obtain a straight line with the bead. Although technically a tooled joint, the beaded tooler does not produce the same mortar surface compaction 3g) Squeezed Joint 3h) Struck Joint 3i) Raked Joint as a concave or V-shaped tool. In addition, the protruding bead can allow water, ice or Note that not all joint profiles are appropriate for all exposures. snow to collect. Therefore, beaded joints are not recommended for weather-exposed Figure 3—Mortar Joint Profiles

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construction. Flush joints (Figure 3f) are typically specified when a wall will be plastered. Excess mortar is simply struck off the face of the wall with the trowel, then dressed with a brush or other tool. Squeezed or extruded joints (Figure 3g) are made using excess mortar that is squeezed out as units are laid. They may be specified for interior walls. Struck joints (Figure 3h) provide a strong horizontal line, similar to weather joints, however because the shape provides a ledge for rain, ice or snow, they are not recommended for walls that will be exposed to weather. Raked joints (Figure 3i) provide a dramatic contrast between the units and mortar joints. They are formed using a joint raker, which removes the mortar to a maximum depth of 1/2 in. (13 mm). With raked joints, small imperfections on unit edges can be more noticeable, because the mortar is not compacted against the unit (the compaction tends to fill in small surface irregularities along the unit edge). The resulting joint is not weather-resistant, and may not leave enough mortar cover over horizontal joint reinforcement (joint reinforcement is required to have 5/8 in. (16 mm) mortar cover in walls exposed to weather or earth (refs. 6, 7)). A better option for exterior surfaces is to specify an integrally colored mortar to provide the visual contrast. Mortar Joint Color Choosing a specific mortar color allows additional creativity by specifying integral color to either provide a visual contrast or to match the unit color, as shown in Figure 4. Note that using a mortar color that matches the surrounding units minimizes the effects of minor mortar staining; i.e., with a contrasting mortar color, greater care should be used to remove mortar droppings and splatters from the masonry units. Because foreign material in mortar sand can affect the mortar quality, as well as appearance, ASTM C144, Standard Specification for Aggregate for Masonry Mortar (ref. 8), limits deleterious substances in aggregates for masonry mortars. Sand can also affect mortar color: sands from different natural sources may have different hues. Therefore, all of the sand for a particular project should come from the same source. Silica sand, which is more expensive than typical masonry sand, is often specified for white mortar. Consistent batching and mixing procedures also help produce uniform mortar color from batch to batch. See TEK 3-8A, Concrete Masonry Construction (ref. 9), for further information. Using a consistent amount of mix water is important to maintain color uniformity for all mortars and especially when using integrally colored mortar. Changing the amount of water can significantly change the resulting mortar color intensity. For this reason there are special methods and equipment, such as shading materials and equipment from direct sunlight, the use of cooled water, and the use of damp, loose sand piles to reduce excessive 4

retempering. Mortar that is too stiff or older than 2 1/2 hours after initial mixing is to be discarded. EXPECTATIONS FOR UNITS AND CONSTRUCTION Aesthetics in ASTM C90 ASTM C90 provides minimum requirements for concrete masonry units that assure properties necessary for quality performance. The specification includes requirements for materials, as well as dimensional and physical requirements such as minimum compressive strength, maximum water absorption, maximum dimensional tolerances, and maximum linear drying shrinkage. It also includes finish and appearance criteria for concrete masonry units. It should be noted that the requirements in ASTM C90 are intended to address the performance of the masonry units when installed, not the aesthetics of the units nor of the constructed masonry. The time for product inspection is before placement. As such, the finish and appearance criteria, for example, prohibits defects that would impair the strength or permanence of the construction, but permit minor cracks or chips incidental to usual manufacturing, shipping and handling methods. Qualities that are not included in C90 include color, surface texture, surface features such as scores or flutes, density choice, water repellency, fire resistance rating, thermal properties and acoustic properties. If required, these properties must be addressed in project contract documents. ASTM C90 does, however, include acceptance criteria for unit color and surface texture: namely, that the finished unit surfaces that will be exposed in the final structure conform to an approved sample of at least four units. The sample should represent the range of color and texture permitted on the job. As a practical matter, color and texture should be expected to vary somewhat due to the nature of the material. The ASTM C90 specification is described in more detail in TEK 1-1E, ASTM Specifications for Concrete Masonry Units (ref. 10). Considerations for Integrally Colored Smooth-Faced Units Integrally-colored concrete masonry units are available in a wide variety of colors and shades. The mineral oxide pigments are evenly dispersed throughout the concrete mix, producing a low-maintenance enhancement that lasts the life of the structure. During unit manufacture, the integrally-colored concrete mix is placed into a steel mold, which is stripped off while the concrete is still plastic. This stripping of the mold draws moisture and coloring pigment to the unit surface, which impacts the surface appearance. On split-faced or ground-faced units, this surface is either ground away or not exposed (in the case of split-faced units). Because the 193

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construction. The permissible tolerances are intended to ensure that misalignment of units or structural elements does not impede the structural performance of the wall. Although the tolerances are not intended for the purpose of producing an aesthetically pleasing wall, these tolerances are generally adequate for most aesthetic applications as well. If tighter tolerances are desired, they must be specified in the project documents. Construction Tolerances As an example, unless otherwise specified, the The International Building Code and Specification for actual location of a masonry element is required to Masonry Structures (refs. 6, 7) contain site tolerances for be within a certain tolerance of where the element is masonry construction which allow for deviations in the shown on the construction drawings: + 1/2 in. in 20 ft, + 3/4 in. max (+ 13 mm in 6.2 m, + 19 mm max). More precise placement dimensions can be specified, typically at a higher cost. Tolerances apply to: plumb, alignment, levelness and dimensions of constructed masonry elements, location of elements, levelness of bed joints, mortar joint thickness, and width of collar joints, grout spaces and cavities. A full discussion of code-required masonry construction tolerances is presented in TEK 3-8A, Use of complementary mortar to emphasize pattern Concrete Masonry Construction (ref 9). formed surface is the final exposed surface on smoothfaced units, however, these units will have a wider color variation than is seen with split-faced or ground-faced units. Understanding this color variation will help avoid possible disappointment that the finished wall does not have the color uniformity of a painted or stained wall.

MODULAR COORDINATION

Ground face units with complementary mortar

Glazed units with contrasting mortar

Figure 4—Examples of Contrasting and Complementary Unit and Mortar Colors NCMA TEK 5-16

Concrete masonry structures can be constructed using virtually any layout dimension. However, for maximum construction efficiency, economy, and aesthetic benefit, concrete masonry elements should be designed and constructed with modular coordination in mind. Modular coordination is the practice of laying out and dimensioning structures to standard lengths and heights to accommodate modularlysized building materials. 194 5

Standard concrete masonry modules are typically 8 in. (203 mm) vertically and horizontally, but may also include 4-in. (102-mm) modules for some applications. These modules provide the best overall design flexibility and coordination with other building products such as windows and doors. Designing a concrete masonry building to a 4- or 8-in. (102- or 203-mm) module will minimize the number of units that need to be cut, providing a more harmonious looking masonry structure. TEK 5-12, Modular Layout of Concrete Masonry (ref. 11) provides details of modular wall layouts and openings. CONTROL JOINTS Control joints, a type of movement joint, are one method used to relieve horizontal tensile stresses due to shrinkage of concrete products and materials. They are essentially vertical planes of weakness built into the wall to reduce restraint and permit longitudinal movement due to anticipated shrinkage. When control joints are required, concrete masonry requires only vertical control joints. When materials with different movement properties are used in the same wythe (such as clay masonry and concrete masonry), this movement difference needs to be accommodated, and may require horizontal movement joints as well (see the Banding section, below). Recommendations for control joint spacing, locations and construction details can be found in TEK 10-2C, Control Joints for Concrete Masonry Walls—Empirical Method, TEK 10-3, Control Joints for Concrete Masonry Walls—Alternative Engineered Method, and TEK 10-4, Crack Control for Concrete Brick and Other Concrete Masonry Veneers (refs. 12, 13, 14). Aesthetically, control joints typically appear as continuous vertical lines in the field of the masonry walls, and perhaps at other areas of stress concentration, such as adjacent to openings, at changes in wall height, etc. Several strategies can be used to make control joints less noticeable. Perhaps the simplest approach is to align the control joint with another architectural feature, such as a pilaster or recess in the wall. In this case, the vertical shadow line provided by the architectural feature provides an inconspicuous control joint location.

veneer has also become very popular. The architectural effect is very pleasing; however, proper detailing must be provided to accommodate the different movement properties of the two materials to prevent cracking. The detail shown in Figure 6 has demonstrated good performance in many areas of the United States and is the preferred detail, as it is economical and maintenance free. Horizontal joint reinforcement is placed in the mortar joints above and below the band, as well as in the band itself if it is more than two courses high. In addition, lateral support (wall ties) are provided within 12 in. (305 mm) of the top and bottom of the band and the band itself must contain at least one row of ties. Some designers prefer placing joint reinforcement in every bed joint of the concrete masonry band. In this case, a tie which accommodates both the tie and reinforcement in the same joint (such as seismic clips) should be used. Another, but less recommended, option is to use horizontal slip planes between clay masonry and the concrete masonry

BANDING Concrete masonry banding is successfully used in many architectural applications. Banding can be accomplished with different colors of block; with different textures, for example a smooth-faced band in a split-faced wall (see Figure 5); with different unit sizes, such as the use of a 4-in. (102-mm) high band in a wall of 8-in. (203mm) units; or with a combination of these techniques. Combining masonry units of different size, color and finish provides a virtually limitless palette. The use of concrete masonry bands in clay brick 6

Figure 5—Banding Example: Split-Faced Bands in Ground Face Field 195 NCMA TEK 5-16


Vapor retarder, per local practice Adjustable ladder wall tie (hot dipped galvanized) @ 16 in. (406 mm) o.c. vertical

Clay brick Joint reinforcement, W1.7 (9 gage) (MW 11) at 16 in. (406 mm) o.c. or equivalent

Closed cell rigid insulation, as required

Concrete masonry accent band

Air space, 1 in. (25 mm), min., 2 in. (51 mm) preferred


Figure 6—Banding Detail: Concrete Masonry Band in Clay Brick Veneer

Light from surface-mounted fixture

Offset, diffuse and/or partially blocked light from wall-mounted fixture

Unwanted Unwantedlong long shadow shadow

Allowable offset from materials, construction, and combined movements

Low to subliminal light = darkened area: no shadows

Figure 7—Use of Diffuse Lighting to Control Shadows NCMA TEK 5-16

band (see TEK 5-2A, Clay and Concrete Masonry Banding Details, Reference 15). The maximum spacing of expansion joints in the clay masonry wall should be reduced to no more than 20 ft (6.1 m) when concrete masonry banding is used. When the clay masonry expansion joint spacing exceeds 20 ft (6.1 m), an additional control joint should be placed near mid-panel in the concrete masonry band, although the joint reinforcement should not be cut in this location. At locations of expansion joints in the clay masonry, joints should be continued through the concrete masonry band and the joint reinforcement cut at these locations. TEK 5-2A provides a fuller discussion and additional details for combining these two materials, including details for incorporating clay masonry bands into concrete masonry walls. LIGHTING DESIGN CONSIDERATIONS FOR CONCRETE MASONRY WALLS

Masonry has historically been associated with diffuse illumination located on or recessed into ceilings, as step (walkway) fixtures located below the waist, or generally placed at a distance from the masonry wall assembly. Diffuse lighting does not concentrate a focused beam but rather spreads the light to provide soft illumination. Although this is sometimes accomplished using an array of many individual light sources at a distance, it is more typically accomplished with fixtures and devices made for this purpose. When wall-mounted light sources are necessary, there are specialized fixtures adapted for masonry that internally refract, reflect, deflect, partially block, diffuse, and/or shade light from directly impinging on the wall surface. Often, the fixture includes additional light diffusers facing away from the wall surface to assist in softly lighting the adjacent area. No noticeable shadows are cast onto the wall, because the shadow is intentionally located away from the wall surface, thus masonry aesthetics are enhanced with a lower lighting intensity and more graceful illumination. These concepts are illustrated in Figure 7. Non-diffuse light shining onto a concrete masonry wall from a surface-mounted light fixture or sconce can sometimes cast unwanted long shadows, giving the erroneous visual appearance of unacceptably poor materials or workmanship (see Figure 7). With nondiffuse light, glossy surface treatments and coatings could also inadvertently magnify this problem. Welldesigned diffuse light can eliminate such concerns. Certain concrete masonry units, such as ground 196 7

face (also called honed or burnished), can be highly reflective. Figure 8 shows a residential project using a custom-fabricated white ground face block. The designer used a complementary balance of several lighting fixtures with what might have otherwise been a challenging masonry reflective finish. The harmonious use of interior lighting combined with exterior overhead (recessed trim) and step lighting is an effective way of solving this challenge.

Figure 8—Diffuse Lighting With Ground Face Concrete Masonry REFERENCES

1. Cleaning Concrete Masonry, TEK 8-4A. National Concrete Masonry Association, 2005. 2. Architectural Concrete Masonry Units, TEK 2-3A. National Concrete Masonry Association, 2001. 3. Standard Specification for Loadbearing Concrete Masonry Units, ASTM C90-09. ASTM International, 2009. 4. Water Repellents for Concrete Masonry Walls, TEK 19-1. National Concrete Masonry Association, 2005. 5. J. A. Farney, Melander, J. M., and Panarese, W. C., Concrete Masonry Handbook for Architects, Engineers, Builders, Sixth Edition, Engineering Bulletin 008. Portland Cement Association, 2008. 6. International Building Code, International Code Council, 2009. 7. Specification for Masonry Structures, TMS 602/ACI 530.1/ASCE 6. Reported by the Masonry Standards Joint Committee, 2008. 8. Standard Specification for Aggregate for Masonry Mortar, ASTM C144-04. ASTM International, 2004. 9. Concrete Masonry Construction, TEK 3-8A. National Concrete Masonry Association, 2001. 10. ASTM Specifications for Concrete Masonry Units, TEK 1-1E. National Concrete Masonry Association, 2007. 11. Modular Layout of Concrete Masonry, TEK 5-12. National Concrete Masonry Association, 2008. 12. Control Joints for Concrete Masonry Walls—Empirical Method, TEK 10-2C. National Concrete Masonry Association, 2010. 13. Control Joints for Concrete Masonry Walls—Alternative Engineered Method, TEK 10-3. National Concrete Masonry Association, 2003. 14. Crack Control for Concrete Brick and Other Concrete Masonry Veneers, TEK 10-4. National Concrete Masonry Association, 2001. 15. Clay and Concrete Masonry Banding Details, TEK 5-2A. National Concrete Masonry Association, 2002. 16. Architectural Enhancement; Aesthetical Design With Concrete Masonry, NCMA AIA/CES Provider Program #000530. National Concrete Masonry Association.




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