04 Scaffolding (Gg)

SCAFFOLDING

CONSTRUCTION TECHNOLOGY IV

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CONTENT Introduction Basic forms of Scaffolding Other forms of Scaffolding ± Sl Slun Slung ung g Scaf Sc Scaffold affo fold ld ± ± TrussTruss-out -out Scaffold ± Sus Suspen Suspended pended ded Sca Scaff Scaffold ffol old d ± Mobile Mobil Mo bile e Tower Tower Scaffold Scaffol Scaf fold d ± Bir Birdc Birdcage dcage age Sca Scaff Scaffold ffold old ± ± Gantries Gan anttries ± Sy Syst System stem em Scaf Sc Scaffold affo fold ld CONSTRUCTION TECHNOLOGY IV

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INTRODUCTION Definition:: Definition Temporary erections, constructed to support a number of platforms at different heights to enable workmen to reach their work and to permit the rising of materials.


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FUNCTION 

As a working platform - so that that the worker worker can stand stand on the the platform platform do the work easily & safely

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As a platform for placing material m aterial & logistic needed by the workers to carry out their job

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As a platform and walking passage - scaffolding scaffoldin scaffo lding g support support the platform platform platf orm that been been used by the worker as their walking path to transport the material & logistic

Types Tubular metal Woods Bamboo Metal frame

Bamboo Scaffolding Use by Chinese (almost 5000 years!) Is a slender structure of bamboo pieces 2 general types: single layered and double layered Single layered layered : working scaffolds, use for light duty works Double layered: layered: finishing scaffold,

STEEL SCAFFOLD 

Steel tubes are nearly 3 times heavier than aluminium alloy tubes but are far stronger.

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Longer span can be used since it deflection is approximately 1/3 of aluminium alloy tubes.

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There 2 types that is: - Galvanized Galva Gal vaniz nized ed steel steell tubes stee tubes - Ungalvanized Ungalvan Unga lvanized ized steel steel tubes tubes that need need special special care (painting, varnishing or oil bath after use)

Steel Scaffolding

ALUMINIUM SCA FFOLDS 

Need protective treatment when they are to be used in contact with materials m aterials such as damp line, wet cement & sea water to prevent corrosion to the tubes.

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Coating the tube with bitumastic paint before using it would be a suitable protective treatment.

Aluminium Scaffolding

TIMBER SCAFFOLD 

Extensively used in the developing country

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Members are lashed together with wire or rope instead of the coupling fittings used with metal scaffolds.

Timber Scaffold

A Scaffold should: Be stable Have a firm base Have properly constructed standards standards,, ledgers ledgers,, transoms and bracers Have a suitable working platform Have guard rails in place Be inspected where required Be constructed so that the public are not put at risk CONSTRUCTION TECHNOLOGY IV

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ross-Section Cross-

of Scaffolding


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Components Componen ts of scaffolds Base Standards Ledgers Transoms Bracing Working platforms Platform width Toeboards and guardguard-rails -rails Brickguards Means of access CONSTRUCTION TECHNOLOGY IV

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DOUBLE COUPLER

STANDARD

BASE PLATE

STANDARD

Base Plate good base is essential and the ground should be leveled and rammed to give a firm surface. Timber sole plates, at least 219mm wide and 35mm thick should be laid to support the base plates for standards. A

Wherever possible, a sole plate should support at least two standards, to ensure that the load carried by each standard is distributed over a fairly large area.


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Base Plate


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Base Plate


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Standards The independent tied scaffold has two vertical rows of standards. These are an inner row about 325mm from the building, - to give give a working working worki ng clearance clearanc clear ance e near the wall and an outer row in line with the inner standards to provide a platform of the width required. Any joints necessary in standards to reach the required height should be staggered and occur near ledgers. CONSTRUCTION TECHNOLOGY IV

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Ledgers

The standards in each row are kept equal distance and strengthened by ledgers, fixed horizontally on the inside of standards with right angle couplers.


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Ledgers


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Transoms Transoms, keeping the inner and outer rows row s of standards evenly apart, are set on top of ledgers at right angles to them and to the building. Horizontal distance between transoms at working w orking platform platform level is determined by the thickness of boards to be used. Ledgers and transoms should not protrude more than is necessary beyond the general outline of the scaffold. At lower low er level - dang danger er to to pedestrians pedestrian pedes trians s or passing vehicles and it is good practice to use safety caps on the open ends.


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Bracing Bracing is essential to stiffen the structure.


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Bracing


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Working Platforms The minimum width of a working w orking platform is 600mm. The surface of the working w orking platform should be even to prevent anyone anyone tripping. tripping. Each board board should should have at least three supports unless its thickness or span is enough to prevent any sagging under load. All boards should be marked with w ith their maximum maximum span. The maximum span should be 1.2m between supports. All boards should be laid closely together along their length. Standard boards are nominal 225mm wide x 38mm thick.


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Platforms Width Platforms should be wide enough to permit freedom of movement and to accommodate accommod ate whatever materials need to be stored for short periods.


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Toeboards and

uard-Rails -Rails Guard-

Toeboards and guardguard-rails -rails are required at the outsides and ends of all working w orking platforms platforms from which men and materials can fall more than 2m. Toeboards and guardguard-rails -rails should be fitted on the inside of standards to prevent outward outw ard movement. movement. Toeboards should rise at least 150mm and the main guard--rail guard -rail must be at least 910mm above the working platform. There must be an unprotected gap of more than 470mm in height in the means of protection against a fall of a person from the working w orking platform. platform. In practice therefore, either an intermediate guardguard -rail -rail or other form of effective barrier example brickguard frames ± ± must must be be filled. filled fill ed..


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Brickguards Brick guards are constructed of wire mesh with three hooks at the top that will be hung over the top rail of the scaffold. The lowest part then hands inside the toe board and this prevents a person or material from falling through the space between the top handrail and the working platform. CONSTRUCTION TECHNOLOGY IV

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Means of Access Access to the scaffold must be by the use of a secure ladder. Under no circumstances should should a person be allowed allowe d to climb up the scaffold tubes to gain access. The safety issues in the use of ladder have been covered in previous note.


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Connector Double Coupler - the only only real real loadbe loa loadbearing dbearin aring g fitting used in scaffolding - used to to join ledgers ledgers to standards standard stan dards s Swivel Coupler - Composed Composed of 2 single single coupler coupler riveted riveted together together togethe r so that it is possible to rotate them & use them for connecting 2 scaffold tubes at any angle. Putlog Coupler - use solely solely for for fixing fixing putlogs/transoms putlogs/transo putlogs/t ransoms ms to the the horizontal ledgers.

Putlog Coupler

Double Coupler

Swivel Coupler

Base Plate For Scaffold

SCAFFOLD TYPE AND SELECTION Selecting

a Scaffolding System The safe and efficient use of scaffolding depends, first of all, on choosing the right system for the job. If the scaffold¶s basic characteristics characteristics are unsuited to the task, or if all the necessary components are not available, proper erection and use is compromised. Selection of scaffolding and related components requires an understanding of site conditions and the work to be undertaken. The employer must consider the following: Basic Considerations: w orkers, tools, materials and equipment to ± the weight of workers, be carried by the scaffold system (safe work w ork load) ± site conditions (interior, exterior, backfill, concrete floors, type and condition of walls, access for the equipment, variations in elevation, anchorage points, etc) CONSTRUCTION TECHNOLOGY IV

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± height to which the scaffold may be erected (overhead power lines, tietie-backs) -backs) ± type of work that will be done from the scaffold (masonry work, sandblasting, painting, metal siding, mechanical installation, suspended ceiling installation) ± duration of work ± weather conditions, including wind and ice build--up build -up ± requirements for pedestrian traffic through and under the scaffold area ± means of access to the scaffold ± configuration of the building or structure being worked on ± special erection or dismantling circumstances. CONSTRUCTION TECHNOLOGY IV 38 ± hoarding

BASIC FORMS OF SCAFFOLD Putlog Scaffold ± ± sin single gle row of uprights uprigh upr ights ts or standards set outside the perimeter of the building & partly supported by the structure Independent Scaffold Scaffold ± ± tw two o row rrows ows s of of standards set outside the perimeter of the building ± ± not dependent depende depe ndent nt on on building building buildi ng support. CONSTRUCTION TECHNOLOGY IV

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Putlog Scaffold


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INDEPENDENT SCAFFOLD


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INDEPENDENT SCAFFOLD


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OTHER FORMS OF SCAFFOLD

Slung Scaffolds: Scaffolds: ± Susp Su Suspended spe ended by by me m means eans o off wir w wire ire e rop ro ropes pes or or chains and are not provided with a means of being raised or lowered by a lifting appliances. ± M Main ain ai n use u use: se:: for for ga gain gaining inin ing g acce ac access cess ss to hi high gh ceilings ceililing cei ngs s or the underside of high roofs.


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Slung Scaffolds At least six evenly spaced suspensions wire ropes/ chains should be used and these should be adequately secured at ends. Working platform is similar to conventional in access of 2.400 x 2.400 plan size.


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Truss--out Truss -out scaffolds: A form of tied t ied scaffold, which rely entirely on the building for support. Used where it is impossible to erect a conventional scaffold from ground level. The supporting scaffolding structure which projects from the face of the building is known as trusstruss -out. -out.


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TRUSS OUT SCAFFOLD


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Suspended Scaffolds: Consist of working platform suspended from supports such as outriggers, which cantilever over the upper edge of building. As a temporary means of access to the face of a building for the purpose of cleaning and light maintenance work. Cradles may be single units or grouped together to form a continuo c ontinuous us working platform; if grouped, they are connected to one another at their abutment ends with hinges which form a gap n.e 25mm wide. CONSTRUCTION TECHNOLOGY IV

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Suspended Scaffolds


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Mobile Tower Scaffolds: Used mainly by painters and maintenance staff to gain access to ceilings c eilings ± ± ca can n be be eas e easily asilily y& readily moved to a new position. A square tower constructed & mounted on wheels and fitted with brakes. Inclined ladders or vertical ladder fixed inside or outside the tower tower - must be secured secured secur ed with with wire wire lashing & provided with bottom transom support.


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Mobile Tower Scaffolds: To ensure stability, the height to working platform of the tower should not exceed three and a half times its least base dimension for internal work. Three times its least base dimension is the maximum for external work. The maximum overall height is 9.6m, unless tied to the structure. CONSTRUCTION TECHNOLOGY IV

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Birdcage Scaffold: Used to provide a complete working platform at high level over a large area and consist basically of a twotwo-directional -directional arrangement of standards, ledgers and transom to support a close close--boarded -boarded working platform at the required height. To ensure stability, standards should be placed at not more than 2.400 centers in both directions and the whole arrangement braced.


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Birdcage Scaffold


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Gantries Used primarily as elevated platforms over a public footpath where the structure under construction or repair is immediately im mediately adjacent to the footpath. Can served as a storage and accommodation accomm odation area as well as providing staging from which a conventional independent scaffold to provide access to the face of the building can be erected. CONSTRUCTION TECHNOLOGY IV

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System Scaffold Based upon the traditional independent scaffold ± instead being connected connected by a series of loose couplers & clips ± ± used integral integral interlocking interlockin inte rlocking g connections. Easy to erect, adaptable & can be assemble and dismantle by a semisemi -skilled -skilled operative operatives. s. Advantage ± ± the elimin eliminatio elimination ation n of internal internal cross cross bracing, giving a clear walk through at all levels even though facade ± ± bra bracin bracing cing g is req requir required. uired ed..


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ERECTION NOTES COMMON TO ALL SCAFFOLDS: oundation: Foundation: Ensure the ground is suitable ± ± we wellll compacted compac comp acte ted d and free from irregularities irregularities ± ± ca caus caused used ed th the e sole sole board unstable. Use base plate for for ± ± scaffold scaffold pitched pitched on soil, pavements, and floor surfacessurfaces - mos mosai mosaic, aic, c, marble. marbl mar ble. e. Sole board to hard ground (min.); 219mm square x 35mm thick.


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ERECTION NOTES COMMON TO ALL SCAFFOLDS: Ditto to medium ground; 219mm wide x 480mm long x 35mm thick. Ditto to soft ground; 219mm wide x 750mm long x 35mm thick. Good practice to use one length of board to support two standards. For heavy loads concentration or double standards, double thickness boards or larger timbers may be required.


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ERECTION NOTES COMMON TO ALL SCAFFOLDS: Basing Out: The following maximum bay centers should not be exceeded for independent, putlog or birdcage scaffolds: Very Very duty

2..7 2. 7 7m m

light light Birdcage scaffold

2 2...5 5 5m m

Ligh Li Light ghtt D Duty Du utty y

General General Purpose

Heavy duty Heavy dut uty y Heavy Heavy duty duty (bkwk) (masonry)

2 2...4 4m 4m

2 2..1 .1 1m m

2 2..0 .0 0m m


1 1...8 8 8m m

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ERECTION NOTES COMMON TO ALL SCAFFOLDS: +/-

Maximum 1500mm on lift height

20mm in 2m lift with a maximum of 50mm deviation over full height.

+/-

Maximum 200mm on bay length

20mm in 2m bay with a maximum of 50mm deviation over full length

Erection Tolerances olerances:: Plumb and level all standards and ledgers progressively as erections of scaffold proceeds.


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ERECTION NOTES COMMON TO ALL SCAFFOLDS: Lift Heights: For

base lifts where access under is required, a maximum lift height of 2.7m is allowable. For

general walkthrough access on upper lifts, a maximum lift height of 2.0m should be maintained.


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ERECTION NOTES COMMON TO ALL SCAFFOLDS: Ledgers:: Ledgers Jointing should be made preferably with sleeve couplers but where expanding joint pins are used, they should be positioned as close to the ledger/ standard connection as possible but not more than 1/3rd. All joints should be staggered in adjacent lifts. Connect ledgers to standards with right angle couplers.


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ERECTION NOTES COMMON TO ALL SCAFFOLDS: Transoms & Putlogs: Putlogs : Should be fixed to the ledgers with right angle or putlog couplers. For

unboarded lifts, transom should be positioned within within 300mm of the standard and connected to the ledgers with right angle couplers.


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ERECTION NOTES COMMON TO ALL SCAFFOLDS: ± ± S Standards: tandards: All standards should be pitched on base plate. Joints in standards should be made with sleeve couplers or expanding joint pins staggered in adjacent bays. Where tension is developed in a standard then the jointing should only be made with sleeve couplers or parallel laps.


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ERECTION NOTES COMMON TO ALL SCAFFOLDS: Couplers:

Can

be classified into two categories: Load bearing couplers

Right angle couplers Swivel couplers 5KN Brace coupler Sleeve coupler Adjustable Fork Heads Adjustable Base Plate/ jack jack

Non-load bearing Putlog Putlog cou couple couplers plers rs couplers Expand Exp Expanding anding ing Join Joint Jointt Pi Pine ne Toe b boa board bo oard ard rd cli clips ps CONSTRUCTION TECHNOLOGY IV

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ERECTION NOTES COMMON TO ALL SCAFFOLDS: Bracing: Bracing should be remain in position at all times for stability stability.. Types of bracing: Ledger bracing: bracing: Dog

leg leg br brac bracing acin ing g fixed from ledger to ledger with right angle or 5KN brace couplers, or from f rom standard to standard with swivel couplers at alternate pairs of standards on every lift for full scaffold height.


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ERECTION NOTES COMMON TO ALL SCAFFOLDS: ±

One

way bracing; bracing; fixed from ledger to ledger with right angle or 5 KN braced couplers at alternate pairs of standards on every lift for full scaffold height. ± Where clear access is required required on base lifts, lifts, ledger ledger bracing may be omitted on the base lift provided the lift height does not exceed 2.7m. ± Where clear access is required required on any working working lift lift bracing at every pair of standards standa rds may be inserted from inside ledger to guardrail to increase clear access way.


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DOG LEG BRACING

ONE-WAY BRACIN BRACING G CONSTRUCTION TECHNOLOGY IV

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ERECTION NOTES COMMON TO ALL SCAFFOLDS: Facade

Bracing: All scaffolds should be façade braced either with with ³zig³zig-zag´ -zag´ bracing from bottom to top or by continuous long bracing bracing from bottom to top, each brace assembly must occur along the scaffold at intervals not exceeding 30 m.


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ERECTION NOTES COMMON TO ALL SCAFFOLDS: Plan Bracing : Not normally required on access scaffolds unless there is a point or level on the scaffold where some lateral loading may be applied, such as loading platform or a lift where no ledger bracing can be placed ± ± pla plan n braci br bracing acing ng should should shou ld be be placed under the ledger line and be connected from standard to standard with right angle or 5KN brace couplers. CONSTRUCTION TECHNOLOGY IV

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ERECTION NOTES COMMON TO ALL SCAFFOLDS: Boarded Lifts: All boarded lifts should be closed boarded. Thickness of board

38mm 38mm

Max.. Max between transoms

1.5m

span span Minimum overhang

50mm


Max.. overhang Max over ov erhan hang g

1 150mm 50mm

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SAFETY PRECAUTION     

Standard must be on the same level and vertically straight on the base plate. The supporting platform wood must be supported properly. Working platform must been equipped with safety elements such as hand rail. Scaffold must be inspected at certain times. Use safety tools such as safety boots, safety helmet and etc when using platform.

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Supervision of scaffold erection & progress /safety reports are undertaken by a suitable experience & qualified person that normally occurs: a) within the preceding 7 days b) after adverse weather conditions that may have affected the scaffold¶s strength or stability c) whenever alterations / additions are made to the scaffold

The report made after inspection must consist :  Location & description of scaffold  Date of inspection  Result of inspection, stating the condition of scaffold  Signature & office of the person making the inspection Badly assembled & neglected scaffold have been a significant contributory factor to the high accident rate associated with the construction industry.

PREVIOUS EXAM QUESTIONS The Department of Occupational Safety and Health (DOSH) has come out with a standard guideline to ensure the performances and safety of scaffold while installation being done. Explain briefly these safety measures in conjunction to the following aspects: Foundation

Lift Heights Erection tolerances


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PREVIOUS EXAM QUESTIONS Demolitions give rise to the need for temporary support and to some extent cause consequences to the adjacent structure/building. Explain with the aid of sketches, THREE (3) situations that may justify the use of each of the following in relation to demolition works. You are to make necessary assumptions where appropriate. ± ± ± ±

Shoring Shoring Scaffolding Scaffolding


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PREVIOUS EXAM QUESTIONS Explain FIVE (5) factors influencing the choice of selection for the type of scaffolding to be use.


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PREVIOUS EXAM QUESTIONS (APRIL2005) Scaffolding is a temporary structure which is constructed to support support workmen and materials to be reach at different heights. List all the basic components of scaffold and explain briefly with the aid of sketches, s ketches, the characteristics of two (2) of the of these se component compon components ents s to fulfill fulfill its functionali functio functionality functiona nality lity ty adequately. (15 marks)


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PREVIOUS EXAM QUESTIONS (NOV2005) Scaffolding is a temporary structure which is constructed to support workmen and materials to be reach at different heights. Explain briefly two (2) basic forms of scaffolding: Putlog Scaffold Independent Scaffold (15 marks) CONSTRUCTION TECHNOLOGY IV

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YOUR

TASK

Please update the notes with the required sketches/ drawings or photographs....


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04 Scaffolding (Gg)

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