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CCIP-010

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A cement and concrete industry publication

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Cost Model Study – Commercial Buildings


A comparative cost assessment of the construction of multi-storey office buildings A report commissioned by The Concrete Centre

Francis Ryder, Head of Cost at The Concrete Centre, has project managed this cost model study for commercial buildings. For more information visit www.concretecentre.com/publications A report commissioned by The Concrete Centre

This comprehensive and independent cost study was undertaken to evaluate a number of structural frame options for a three-storey office building in an out-of-town location and a six-storey office building in a city centre location. A total of 14 floor design options were evaluated, budget costings were assigned to all elements of construction and adjustments were made to reflect time-related costs attributable to differences in the construction programme.


The publication outlines the analysis, the detailed costings and programmes for each structural alternative, and provides a useful resource for architects, engineers and contractors involved with evaluating the cost competitiveness of structural options for multi-storey office construction.

CCIP-010 Published October 2007 ISBN 1-904482-36-8 Price Group P © The Concrete Centre

Riverside House, 4 Meadows Business Park, Station Approach, Blackwater, Camberley, Surrey, GU17 9AB Tel: +44 (0)1276 606 800 www.concretecentre.com

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Acknowledgements The Concrete Centre, as the organisation who commissioned this independent study, would like to acknowledge the contributions of the following companies on this project: Allies and Morrison – Architectural Design Established in 1984, Allies and Morrison’s expertise includes master planning, architecture, landscape, design, interior design and conservation. Allies and Morrison routinely work on a number of master plans and played a key role in preparing master plan proposals for the London 2012 Olympics and the regeneration of the Lower Lea Valley. Past award winning commissions include One Piccadilly Gardens, Manchester; the BBC Media Village at White City; Girton College Library and Archive and the British Council in Lagos, Nigeria. www.alliesandmorrison.co.uk Arup - Structural Design. Arup is an international firm of consulting engineers, with over 55 years of international experience in providing consultancy in engineering, design, planning and project management services in every field related to building, civil, and industrial projects. Arup aims to provide a consistently excellent multi-disciplinary service by adding value through technical excellence, efficient organisation, personal service and a strong commitment to sustainable design. www.arup.com Davis Langdon LLP - Quantity Surveying Davis Langdon LLP provides a range of integrated project and cost management services designed to maximise value for clients investing in infrastructure, construction and property, with extensive experience in projects and programmes across a broad range of sectors and building types. Davis Langdon has a culture of achieving excellence and delivers success through limiting risk, forecasting and controlling cost, managing time and resources, and maximising value for money according to the specific needs of the client and brief. www.davislangdon.com Mace - Programming Mace is one of the world’s most diverse management and construction companies and is a renowned global business providing management and construction services to the public and private sectors, with a reputation for finding the best solutions to complex projects. Mace has been responsible for the successful delivery of a number of award-winning projects, including the More London development incorporating City Hall, Heathrow T5 and the City of London’s fourth tallest tower, 51 Lime Street. www.mace.co.uk The following proprietary products are referenced in this publication. Slimdek® is a registered trademarks of Corus UK Ltd. Ribdeck® is a registered trademark of Richard Lees Steel Decking Ltd.

Published by The Concrete Centre Riverside House, 4 Meadows Business Park, Station Approach, Blackwater, Camberley, Surrey GU17 9AB Tel: +44 (0)1276 606800 Fax: +44 (0)1276 606801 www.concretecentre.com CCIP-010 Published October 2007 ISBN 1-904482-36-8 Price Group P © The Concrete Centre Cement and Concrete Industry Publications (CCIP) are produced through an industry initiative to publish technical guidance in support of concrete design and construction. CCIP publications are available from the Concrete Bookshop at www.concretebookshop.com Tel: +44 (0)7004 607777 All advice or information from The Concrete Centre is intended for use in the UK only by those who will evaluate the significance and limitations of its contents and take responsibility for its use and application. No liability (including that for negligence) for any loss resulting from such advice or information is accepted by The Concrete Centre or its subcontractors, suppliers or advisors. Readers should note that the publications from The Concrete Centre are subject to revision from time to time and should therefore ensure that they are in possession of the latest version. Cover photo: Cardinal Place © Anthony Weller/VIEW. Printed by Alden press, Witney, UK.


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Cost Model Study – Commercial Buildings Contents 1.

Summary

3

2.

Introduction

5

3.

Method of study

6

4.

Building A – 3-Storey business park location

11

5.

Building B – 6-Storey central city location

22

6.

Programmes

35

7.

Summary of costs

45

8.

Study findings

49

9.

Commentary from The Concrete Centre

62

A1. Appendix A – Detailed programmes

Commercial Buildings - Cost Mode1 1

68

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Summary

1. Summary This cost model study compares the costs of constructing three- and six-storey commercial buildings using a variety of short-span and long-span options in two different locations, taking into account construction and Category A fit-out, and the effect of programme times on cost. Designs were commissioned for a three-storey office building in an out-of-town business park location in the south east and a six-storey office building located in central London. The buildings were based upon appropriate structural grids commonly in current use, with designs and specifications suited to current market conditions. Architectural design was undertaken by Allies and Morrison, all structural designs were carried out by Arup, and costings were undertaken by Davis Langdon. The designs were taken to normal outline design stage, the only differences being directly attributable to the structural frame material. Budget costings were assigned to all elements of construction, from substructure, superstructure and external envelope through to preliminaries, with the exception of external works, which were considered to be too highly site-specific to permit accurate costing. Adjustments were made to the costings to reflect time-related costs attributable to differences in construction programmes. Whilst identifying the variation in the costs of frames, the study also considers the effects that the choice of framing material and method of construction have on other elements of the building, as well as the other benefits that the choice of frame can generate. The study demonstrates the need to consider all elements of the building cost, rather than simply the cost of the structure, and highlights the extent to which elements other than the structure are affected by the choice of frame solution. In terms of overall construction cost for the three-storey building, the most economic solution was found to be the RC Flat Slab option, closely followed by the steel Composite option (+0.5%), with the Post-Tensioned Flat Slab and In-situ + Hollowcore options in equal third place (+1.2%). The Steel + Hollowcore option was in fifth place (+2.4%), with the Slimdek option being the least economic (+5.1%). In terms of overall construction cost for the six-storey building, the most economic solution was also found to be the RC Flat Slab option, closely followed by the PostTensioned Flat Slab option (+0.1%), with the steel Composite option in third place (+0.9%) and the In-situ + Hollowcore option in fourth place (+1.0%). The Steel + Hollowcore option was in fifth place (+3.5%), with the Slimdek option again being the least economic (+5.0%). Of the two long-span options on this building, the PostTensioned Band Beam option and the Long-Span Composite option are respectively 2.2% and 2.3% more costly than the Flat Slab option.

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Summary

Thus in consideration of the construction cost, an average of 1.0% separates the four most economic short-span options, rising to 5.1% when all six options are considered. For the two long-span solutions considered, the difference in total construction cost is negligible at 0.1%. The main conclusions are that, for modern commercial buildings, the variation in total construction cost is relatively small across the range of structural options considered and that they are all relatively competitive. Clearly, therefore, it is the effect on other construction related factors in the project which need to be considered in the selection of the most appropriate structural choice. Factors such as cash flow, overall project time, fire protection, use of flat soffits and lower floor to floor height are discussed in detail in the study.

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Introduction

2. Introduction This Cost Model Study – Commercial Buildings was undertaken to provide both a comparison and an understanding of the construction costs associated with commercial buildings using a variety of different structural solutions. Cost is usually the major criterion in assessing design and construction alternatives and construction professionals require current studies in order to provide weight to their decisions. The Reinforced Concrete Council (RCC) published a cost model study on commercial buildings in 1993 (GOODCHILD, C.H. Cost Model Study, British Cement Association 97.333, 1993). The Concrete Centre identified that this study needed to be updated because building types in the contemporary market are significantly different from those that formed the basis of the 1993 study. The value of the RCC study was found to be not so much in the cost results but in the detailed and rigorous assessment of how structural frame choice can affect the cost of other items, such as cladding, internal planning, fire protection, services, fit-out, etc. It is the independent assessment of current building types reported in this document that will be of most enduring value to quantity surveyors, architects, engineers and other construction professionals. Thus, The Concrete Centre commissioned a study, undertaken in 2005 and 2006 by the following consultants: Allies and Morrison Architectural Design Arup Structural Design Davis Langdon LLP Quantity Surveying Mace Programming The objective of the study was to provide a cost comparison between various structural options for buildings of three-and six-storeys, on clear sites, in out-of-town and city centre locations respectively. Identical specifications were required, with the only permissible variations being directly attributable to the materials used in the structural frame. It is emphasised that the study was undertaken on an independent basis. The structural design for all options was carried out by Arup and costs were prepared by Davis Langdon, based on pricing data obtained from their national cost database of recent projects and therefore reflecting the current marketplace. Procurement and construction planning/programming studies also formed part of the commissions, in order that the effects of programme on costs could be included. These were carried out by Mace. The cost models were developed using current best practice and are reported upon in this publication. The process of designing and costing alternative methods of constructing otherwise identical buildings raises many interesting issues for those com-missioning, designing and constructing buildings. As will be shown, there are many useful conclusions to be drawn, over and above those relating simply to cost.

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Method of study

3. Method of study Brief

The brief given to the design team asked for the outline designs of multi-storey buildings on open clear sites, one case being an out-of-town business park in the south east and the other case being in central London. The designs were to reflect contemporary commercial practice and the design team’s best judgement. They would be used for preparing budget costs and for making comparisons of the effects of the choice of different structural frames. The choice, size and location of the buildings to be investigated were based on the design team’s judgement of current commercial practice and demand, and to avoid unduly favouring one structural solution over another. Designs were commissioned for a three-storey office building in an out-of-town business park location in the south east (Building A) and a six-storey office building located in central London (Building B). The buildings were based upon appropriate structural grids commonly in current use, using pad or piled foundations. Specifications were suited to current market conditions, which suggested that Building A be an air-conditioned, L-shaped building with curtain walling and some natural ventilation and that Building B be a rectangular, air-conditioned building with curtain walling. Building A was chosen to reflect a framed building of average size (4,650m2) in a commercial/business park setting. It is representative of a typical low-rise building in the centres of current development activity. Building B, containing retail space at ground floor level, was chosen to reflect a high-quality framed building of average size (14,200m2 of offices and 2,300m2 of retail space) in Central London. It is acknowledged that a building of this type in London would normally have a basement. However, it was considered that inclusion of this element could unduly favour some of the structural options over others above ground. Accordingly, the basement construction has been excluded from the study.

Concepts and initial studies

The shape and form of the buildings were determined to suit typical market requirements in terms of performance and cost. Indicative sketches for the two buildings, showing the building form, follow on page 7.

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Method of study

Building A: Three-storey.

Building B: Six-storey.

Typical floor plans and cross-sections for both building projects used in this study

The form of Building A is an L-shape with a full-height atrium, a central service core and secondary stairs and service access located towards the ends of the building, with a limited amount of undercroft parking. Air conditioning is provided by a fan-coil system providing full climate control when active. The internal environment is designed to maximise daylighting and allow some mid-season free cooling from natural ventilation, which saves energy and lowers CO2 emissions. This is achieved with floor plates 23.5m wide, configured around a grid of three bays of 7.5m, allowing a degree of cross-ventilation from the perimeter windows. The building envelope comprises grid stick curtain wall cladding, incorporating floor to ceiling double glazing units and aluminium clad insulated spandrels, permitting good daylighting to most of the working areas.

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Method of study

The form of Building B is rectangular, arranged around a central atrium and incorporating a fan-coil unit air-conditioning system, with service cores located towards the ends of the building. The form of the building is designed with a low envelope to volume ratio, which, in addition to maximising investment return, helps minimise heat loss during the winter. The building is fully sealed, requiring full climate control year round. The building envelope comprises unitised curtain walling, incorporating floor to ceiling double-glazing units and stone clad insulated spandrels. The floor plate depths are 9.5m to the core walls on the E-W axis and 15.5m to either the core walls or the atrium on the N-S axis. The building can be operated with single or split tenancies, with splitting by vertical division and requiring a glazed wall to the atrium. Layouts involving circular columns and cantilevers were not pursued (other than the inclusion of two feature columns to the edge of the atrium on Building A) as they may have unduly favoured some structural solutions over others. Also, utilisation of exposed concrete inside the building to reduce capital and running costs of the air conditioning by using the thermal mass of the structure has not been considered in the base case comparison, as this may also have unduly favoured some structural solutions over others. This is a potential benefit which is discussed further in Chapter 9 - Commentary from The Concrete Centre. Investigations to determine the optimum structural grid for the proposed buildings were carried out. Grids of 7.5 × 7.5m, 9.0 × 6.0m and 9.0 × 9.0m were considered. For Building A, a 7.5 × 7.5m grid was established as optimum and was adopted for all frame options in the study, long spans not being considered appropriate. For Building B, a 7.5 × 9.0m grid is more representative of the current market for a city centre site. It also permitted exploration of a long-span option in the study, by creating a 15.0 × 9.0m grid. The resulting gross floor areas were to be approximately 1,500m2 per floor based on a 7.5 × 7.5m structural grid for Building A and approximately 2,750m2 per floor based on a 9.0 × 7.5m structural grid for Building B. For Building A, six options were developed. For Building B, six options were developed for the short-span situations (7.5m) and two options for a long-span situation (15.0m), giving eight options in total. The structural options were chosen as being representative of current best practice and most likely to be proposed by the design team for a commercially viable project. Indicative diagrams and descriptions for each of the options are shown in the figures which follow.

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Method of study

Short-span options - Building A and B Option 1 - Flat Slab

Reinforced In-situ concrete flat slab and columns

Option 2 - Composite

Steel beams and metal decking, both acting compositely with In-situ concrete floor slabs. Steel columns

Long-span options - Building B only Option 3 - PT Flat Slab

Option 7 - PT Band Beams

Post-tensioned In-situ concrete flat slab and reinforced In-situ concrete columns

Post-tensioned In-situ concrete flat slab and band beams with reinforced In-situ concrete columns

Short-span options - Building A and B Option 4 - Steel + Hollowcore

Option 5 - In-situ + Hollowcore

Option 6 - Slimdek

Option 8 - Long-Span Composite

Steel beams acting compositely with precast concrete hollowcore floor slabs. Steel columns

Reinforced In-situ concrete beams and columns with precast concrete hollowcore floor slabs

Slimdek system comprising asymmetric beams and metal decking, both acting compositely with In-situ concrete floor slabs. Steel columns

Long-span cellular steel beams and metal decking, both acting compositely with In-situ concrete floor slab. Steel columns

Scheme designs

The two buildings were taken up to normal outline design stage. The buildings were all to commercial developers’ standards with associated outline specifications. The only differences were directly attributable to the choice of structural solution. The architectural schemes, layouts and specifications were based on contemporary commercial practice and current regulations. The new Part L of the Building Regulations had not come into effect at the time the designs were undertaken and is not therefore taken into account in the study. Office floors were designed to be for an open-plan configuration on a 1.5m planning module, to allow for possible subdivision of the floors into two tenancies. Cellular office layouts were allowed for. Potential partitions may be aligned with external wall mullions or piers at 1.5m centres. Initial floor plans and core layouts were adjusted and modified following liaison and discussion between the design team members. In particular, core areas were modified as necessary to accommodate structural and engineering services’ requirements and to suit the peculiarities that result from the choice of structural solution. No design was undertaken for external works and landscaping, these aspects being so highly site-specific as to preclude meaningful consideration. The extent, layout and complexity of external works are to a large extent dictated by the size, configuration and orientation of the site for each particular project, together with constraints imposed by location and external factors such as planning. The extent to which external works are likely to be influenced to any significant degree by the choice of structural solution is considered to be minimal, and consequently, consideration of external works is beyond the scope of this study.

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Method of study

The final structural zones represent those considered, by the design team’s experience and judgement, to be optimum depths for the structures.

Specifications and drawings

Design criteria and outline specifications were finalised and scheme drawings were prepared for each building for all structural options. The design information is presented in this document as follows: Design criteria

Architectural, structural and services

Outline specifications

Architectural, structural and services

Architectural drawings Typical floor plans Structural drawings

Partial floor plans and floor zone for each of the following options: Flat Slab In-situ + Hollowcore PT Flat Slab Composite Steel + Hollowcore Slimdek PT Band Beams Long-Span Composite

Basis of costing and quantities

Costings were based on drawings and specifications prepared for all options, for both buildings. Structural schemes were prepared for each frame option to allow for an order of cost to be assessed and thus a comparison made (and not for an absolute cost to be determined). The level of information provided on each scheme was equivalent to that which would be prepared in a normal scheme design. Quantities and estimates of cost and areas were prepared from the scheme design information. Budget costings were assigned to all elements of construction, from substructure, superstructure and external walls through to preliminaries, using rates appropriate to the specifications and locations and a base date of June 2006. The costings were presented in the form of summaries and are contained within Chapter 7 Summary of costs, where information on key rates is also presented.

Planning and programming

Detailed construction programmes were prepared on the basis of the drawings, specifications and quantities outlined in this report; these are presented in the form of bar charts and are contained within Chapter 6 Programmes. Procurement programmes and contractor lead times were also considered. A more detailed explanation of the planning and programming, including notes on the assumptions made and the logic used, is given within Chapter 6 Programmes, and examples of the detailed programmes are contained within Appendix A.

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Building A - Design criteria

4. Building A Design criteria Architectural

The following design criteria, representative of current good practice and commercial standards, form the basis of the study. Plan dimensions Planning grid

1500 × 1500mm

Partition grid

1500 × 1500mm

Structural grid

7500 × 7500mm

Vertical dimensions 3950–4160mm (see drawings) Floor to ceiling height

2700mm

Raised floor

250mm

Occupancy Density

One person per 10m2 of nett internal floor area.

Design target populations

Three-storey 407 total, 319 on upper floors.

Ancillary accommodation Core areas

Structural

Include male and female toilets and cleaners’ cubicle on each floor, disabled toilets and PABX equipment on the ground floor.

Codes of practice and standards Concrete

BS 8110 Part 1: 1997 (amendments 1 & 2) - Structural use of concrete

Structural steelwork

BS 5950 Part 1: 2000 - Structural use of steelwork in buildings

Loads Imposed load Dead load Line loads

Offices: 4.0 + 1.0kN/m2 for partitions Roof: 0.75kN/m2 Self-weight plus superimposed dead load of 0.9kN/m2 External cladding Atrium glazing Internal blockwork walls

8kN/m 8kN/m 10kN/m

Deflections General

Deflections will be limited in accordance with the guidance in the appropriate Code of Practice.

Fire rating

1hr

Vibration

Natural frequency limited to 4Hz.

Ground conditions

Services

Bearing pressure

It has been assumed that the site provides a bearing capacity suitable for pad foundations and a ground-bearing ground floor slab with an N value of approximately 30 in a Standard Penetration Test. It has been assumed that the water table is below founding level.

Lateral stability

Frame action

Propping

Propping is required for the Slimdek system during construction. No propping is required for the other steel frames.

General

All normal services to be provided to typical contemporary commercial standards, including: heating, lighting, ventilation, lifts, hot and cold water supply, drainage, fire services, small power, provision for communications, lightning protection, etc.

Ventilation General

Air-conditioned using fan-coil system, with partial natural ventilation.

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Building A - Outline specifications

Outline specifications Architectural

External envelope External wall

Proprietary grid stick curtain walling system, 170mm thick overall.

Internal atrium walls (if required for tenancy split)

Grid stick curtain wall incorporating floor to ceiling single glazing units and aluminium clad spandrels.

Rain screen to stair cores

Aluminium panel rain screen with ventilated insulated cavity supported on slab-bearing blockwork walls or grid frame.

Plant rooms

Proprietary curtain walling panel system.

Plant screen

Coated aluminium louvres connected to steel panels bolted to slab upstands.

Flat roofs

Inverted roof build-up with monolithic hot applied bitumen polymer membrane, insulation and ballast.

Office areas Floors

Proprietary medium duty raised floor system, 250mm overall, and carpet.

Ceilings

500 × 500mm pre-finished fully demountable perforated tile with concealed suspension system.

External walls

Grid stick curtain wall incorporating floor to ceiling double glazing units and aluminium clad insulated spandrels. Solar control by soft coat glass and fritting to south/west elevations and soft coat glass to north and east façades. Mullions to be top hung from roof level. Façades incorporate high-level openable vents allowing cross ventilation for daytime cooling during temperate weather and/or night time purging. Operation of the façade vents by remote control to prevent users opening at the wrong times.

Columns

Emulsion-painted plastered concrete or painted dry-lined encased steel columns.

Skirtings

Recessed flush painted softwood.

Entrance halls/ground floor lift lobbies Floor

Carpet.

Walls

Emulsion painted dry-lining or plaster.

Ceilings

Pre-finished 500 × 500mm metal tile with concealed grid.

Skirtings


Furniture

Reception desk.

Doors

Stainless steel revolving doors.

Lift lobbies (upper floors) Floors

Carpet.

Walls


Ceilings


Toilets Floor

Unglazed ceramic tiles.

Walls

Glazed ceramic tiles. Full-height cubicle partitions and doors.

Ceilings


Skirtings

Ceramic tile.

Lighting

Downlighters.

WCs

Suspended WC pans with concealed cisterns.

Wash basins

Fully or semi-recessed vanity mounted hand basins with concealed UPVC pipework, polished granite top.

Urinals

White vitreous china.

Mirrors

Full height and width.

Vanity shelf

Polished granite.

Fittings

Polished stainless steel fittings and shaving point.

Hand drying

Recessed paper towel dispensers.

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Architectural continued..

Staircases Floors

Precast terrazzo (primary stair) or granolithic (secondary stair) treads and risers with non-slip nosings, with mild steel painted stringer.

Walls

Emulsion painted suspended plasterboard dry-lining.

Ceilings


Handrail

Polished stainless steel top and secondary rails.

Balustrade

Polished stainless steel posts.

Internal doors Doors

Hardwood veneered plywood solid core doors with overpanels and painted hardwood frames.

Ironmongery

Polished stainless steel.

Plant spaces

Structural

Enclosed

Floors: screed laid to falls. Walls/ceilings: unfinished structure/blockwork.

Open/external

Precast paving slabs and gravel ballast.

Intake room

Unfinished structure.

Substructures Foundations

Mass/reinforced concrete pads, cast on 75mm blinding on compacted formation.

Slab

Ground-bearing slab with edge thickening and mesh reinforcement to top face. Joints provided with debonded bars on all gridlines to control cracking. Allowance made for lift pits and manholes.

Superstructures

Services

Structural frames

Specification as given on partial floor plans. Plant room enclosures: steel frame (25kg/m2) supporting lightweight cladding.

Fire

One hour fire protection to all structural members apart from roof structure (no fire protection required). The building is not sprinkler-protected.

Air conditioning Design data

22°C dry bulb +/– 1°C. 50% RH +10%/–15% RH. 0.25 air changes per hour for office areas. Internal thermal loads: Occupants Office lighting Office small power

8W/m2 10W/m2 18W/m2

Occupancy

One person per 10m2.

Fresh air allowance

12 litres per second per person.

Supply

All offices air-conditioned by means of four-pipe fan-coil system.

Air handling

Roof-mounted air handling units serving all areas of the building. Chilled water generated by a central refrigeration plant.

Heating General:

Low temperature hot water system. Gas fired boiler plant in roof plant room.

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Services

Ventilation Supply

Vents incorporated within suspended ceiling. All toilet areas provided with mechanical supply and extract system.

Plumbing services Cold water

Rising main to cold water storage tank feeding central core and LTHW system. Separate drinking water system.

Hot water

Hot water from central roof mounted storage feeding core areas.

Roof drainage

Rainwater outlets connected to vertical stacks.

Foul drainage

All foul waste to discharge into Local Authority foul water drainage system.

Fire services

Hose reels.

Control systems Control

All mechanical services plant and equipment controlled by central BMS.

Electrical services Load densities

Offices: Lighting Small power Air conditioning Miscellaneous

12W/m2 15W/m2 60W/m2 10W/m2

Lighting

Generally to L2 office standard; control by switches with key switches for the emergency fittings. Emergency fittings to be self-contained.

Small power

Distribution within raised flooring via floor boxes. Cleaners’ sockets to walls and circulation spaces.

Communications

Provision within floor boxes for tenants’ installations.

Lightning

Protection system complying with BS 6651:1999.

Lift installation Design criteria

Designed to serve an overall, building population of one person per 14 m2. 15% of the design target population to be handled in a five minute period.

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Building A - Architectural drawings

Architectural drawings A

B 7500

C 7500

D 7500

7500

1

7500

2

Full height atrium

E 7500

F 7500

G 7500

H 7500

I 7500

7500

3

7500

4

7500

5

6

Typical floor plan

In the structural drawings which follow, one page is dedicated to each structural option. On each page is part of a typical floor which represents the area highlighted in blue. In addition a cross-section through the floor zone accompanies each plan.

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Building A - Structural drawings

Structural drawings Flat Slab 300 mm RC slab

1. 2. 3. 4.

300mm concrete flat slab to upper floors and roof. Concrete class C 32/40. High-yield reinforcement. Assumed design imposed loads: Roof: 0.75kN/m2 Plant room: 7.5kN/m2 Offices: 5.0kN/m2 5. Vertical dimensions: Slab: 300mm Services zone: 600mm Floor zone = 1050mm Ceiling/lighting: 150mm Floor to ceiling: 2700mm Raised floor: 250mm Total: 4000mm

300

1050 Services zone

600

Ceiling and lighting zone

150

]

Section through floor zone

Stairs

200mm R C Shear walls Void 800 Ø R C Column

7500

Full Height Atrium

7500

800 Ø R C Column

Void

Lifts

7500

7500

Toilet Zone

All Columns 450 x 450 unless otherwise noted

7500

7500

7500

7500

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Composite

130 A193 mesh

457 x 152 UB52 800 (min)

1.2mm ribdeck AL Services zone

1087

350 (min) 150

Ceiling and lighting zone Section through floor zone

1. 130mm lightweight concrete slab on 1.2mm Ribdeck AL on steel frame to upper floors and roof. 2. Lightweight concrete class C 32/40. 3. High-yield reinforcement. 4. Assumed design imposed loads: Roof: 0.75kN/m2 Plant room: 7.5kN/m2 Offices: 5.0kN/m2 5. Vertical dimensions: Slab: 130mm Services zone(1): 807mm Floor zone = 1087mm Ceiling/lighting: 150mm ≈ 1090mm Floor to ceiling: 2700mm Raised floor: 250mm Total: 4040mm

]

C3

203 x 203 UC46 Void

203 x 203 UC46

406 x 140 UB46

Full Height Atrium

508Ø CHS153

457 x 152 UB52

C2 = 254 x 254 UC89 C3 = 305 x 305 UC97

356 x 127 UB33

356 x 127 UB33

356 x 127 UB33

7500

C1 = 254 x 254 UC73

C1

C1

including downstand beams

508Ø CHS153

C3

356 x 127 UB33

356 x 127 UB33

C3

7500

203 x 203 UC46 Stairs

457 x 191 UB82

C3

356 x 127 UB33

6000

457 x 191 UB82

(1)

406 x 140 UB46 7500

457 x 191 UB67

406 x 140 UB46 7500

C1

356 x 127 UB33

356 x 127 UB33

406 x 140 UB46

457 x 152 UB52

C2

C1

406 x 140 UB46 7500

356 x 127 UB33

C3

C2

406 x 140 UB46

356 x 127 UB33

457 x 152 UB52 356 x 127 UB33

356 x 127 UB33

C3

356 x 127 UB33

356 x 127 UB33 C2

C1

356 x 127 UB33

Void

254 x 102 UB25

Toilet Zone

356 x 127 UB33

406 x 140 UB39

406 x 140 UB39

C2

356 x 127 UB33

356 x 127 UB33

7500

C2

C3 457 x 152 UB52

Lift

356 x 127 UB33

457 x 152 UB52 C2

457 x 191 UB82 406 x 140 UB39

356 x 127 UB33

356 x 127 UB33

356 x 127 UB33

7500

C2

406 x 140 UB39

457 x 152 UB52 C2

C1

7500

17


02/10/2007 11:19:27


A142 mesh in 50mm (min) structural topping

150mm hollowcore 200

250

425

450 600 600 Services zone

In-situ + Hollowcore

Typical edge beam 50

600

450

1150

800 (min)

600


350(min) 150

1. 150mm precast concrete hollowcore units with 50mm (min) mesh reinforced structural topping to upper floors and roof. 2. Concrete class C 32/40. 3. High-yield reinforcement. 4. Assumed design imposed loads: Roof: 0.75kN/m2 Plant room: 7.5kN/m2 Offices: 5.0kN/m2 5. Vertical dimensions: Slab and topping: 200mm Services zone(1): 800mm Floor zone = 1150mm Ceiling/lighting: 150mm Floor to ceiling: 2700mm Raised floor: 250mm Total: 4100mm

]


(1)


Stairs 200mm R C Shear walls Void

7500

800 Ø R C Column

Full Height Atrium

7500

800 Ø R C Column

600 x 250 R C Beam (edge)

Void

Lifts

7500

Toilet Zone

7500

600 x 250 R C Beam (trimmer)


7500

600 x 600 R C Beam (typical)

7500

7500

7500

18


02/10/2007 11:19:28


250mm Post-tensioned slab

Reinforcement

PT Flat Slab

250

1. 2. 3. 4.

250mm post-tensioned concrete flat slab to upper floors and roof. Concrete class C 32/40. High-yield reinforcement. Post-tensioning: Each post-tensioning tendon has five No. 12.7 mm diameter strands. 5. Assumed design imposed loads: Roof: 0.75kN/m2 Plant room: 7.5kN/m2 Offices: 5.0kN/m2 6. Vertical dimensions: Slab: 250mm Services zone: 600mm Floor zone = 1000mm Ceiling/lighting: 150mm Floor to ceiling: 2700mm Raised floor: 250mm Total: 3950mm

PT duct 1000

Services zone

600


150


]

Stairs 200mm R C Shear walls Void 800 Ø R C Column

7500

Full Height Atrium

7500

800 Ø R C Column

Void

Lifts

7500

7500

Toilet Zone


7500

7500

7500

7500

19


02/10/2007 11:19:29


A142 mesh in 50mm structural topping

Steel + Hollowcore 1. 200mm precast concrete hollowcore units with 50mm (min) mesh reinforced structural topping on steel frame to upper floors and roof. 2. Concrete class C 32/40. 3. Steel grade S355. 4. Assumed design imposed loads: Roof: 0.75kN/m2 Plant room: 7.5kN/m2 Offices: 5.0kN/m2 5. Vertical dimensions: Slab: 250mm (1) Services zone : 807mm Floor zone = 1207mm Ceiling/lighting: 150mm ≈ 1210mm Floor to ceiling: 2700mm Raised floor: 250mm Total: 4160mm

250

200 mm Hollowcore

457 x 191 UB67

1207 800 (min) 350 (min) 150


]


C2

C2

6000 305 x 305 UC97

Stairs

203 x 203 UC60 Void

203 x 203 UC60

C2 = 305 x 305 UC97 C3 = 305 x 305 UC118 C4 = 305 x 305 UC137

508Ø CHS 153

457 x 191 UB67

406 x 178 UB54

139.7Ф x 5.0 CHS

7500

C1 = 254 x 254 UC89

Full Height Atrium

C1

C2


508Ø CHS 153

C3

406 x 178 UB54

406 x 178 UB54

457 x 191 UB67

C3

7500

203 x 203 UC60

305 x 305 UC97

(1)

406 x 140 UB39

C2

457 x 191 UB74

C2

139.7Ф x 5.0 CHS

7500

C4

457 x 191 UB67

C2

139.7Ф x 5.0 CHS

406 x 140 UB39

C1

139.7Ф x 5.0 CHS

C2

406 x 178 UB54 C4

457 x 191 UB67

457 x 191 UB67 7500

Void

C3

7500

457 x 191 UB67

C4

Toilet Zone

406 x 140 UB39

406 x 178 UB54

152 x 89 UB16

457 x 191 UB67 139.7Ф x 5.0 CHS

C3 533 x 210 UB82

Lifts

406 x 178 UB54

406 x 178 UB54

533 x 210 UB82

457 x 191 UB67

C3

139.7Ф x 5.0 CHS

457 x 191 UB67

C2

7500

139.7Ф x 5.0 CHS

457 x 191 UB67

7500

C2

457 x 191 UB67

Services zone

C2

139.7Ф x 5.0 CHS

C2

7500

20


02/10/2007 11:19:30


Slimdek

In situ concrete slab

1. 342mm (overall) concrete slab on SD225 deep decking on asymmetric steel beams to upper floors and roof. 2. Concrete class C 32/40. 3. Steel grade S355. 4. Assumed design imposed loads: Roof: 0.75kN/m2 Plant room: 7.5kN/m2 Offices: 5.0kN/m2 5. Vertical dimensions: Slab: 342mm Services zone: 600mm Floor zone = 1092mm Ceiling/lighting: 150mm ≈ 1095mm Floor to ceiling: 2700mm Raised floor: 250mm Total: 4045mm

342

A193 mesh SD225 Deep decking 300 ASB 155

1092 600

Services zone

150


]

C3

203 x 203 UC60 Void

203 x 203 UC60

200 ASB124

300 ASB155

C3

7500

203 x 203 UC60 Stairs

305 x 305 UC97

C3

508Ø CHS 153

C3

C1 = 254 x 254 UC89

300 ASB155

6000

305 x 305 UC97


C2 = 254 x 254 UC107

Full Height Atrium

C3 = 305 x 305 UC97 C4 = 305 x 305 UC118

508Ø CHS 153

203 x 102 UB23

300 ASB155

300 ASB155

7500

C5 = 305 x 305 UC137

C3

C1

203 x 102 UB23

203 x 102 UB23

C2

7500

C1

C2

7500

C1

203 x 102 UB23 300 ASB196

C2

203 x 102 UB23

C1

C5

7500

300 ASB155

300 ASB155

C5

300 ASB155 203 x 102 UB23

280 ASB74

300 ASB155

300 ASB155

Toilet Zone

Void

300 ASB155

300 ASB196

300 ASB196

300 ASB155 203 x 102 UB23

300 ASB155

280 ASB74

C5

300 ASB155

7500

C2

C5

Lifts

300 ASB155

300 ASB155

300 ASB155

7500

300 ASB196

C4

C2

C2

203 x 102 UB23

C1

7500

21


02/10/2007 11:19:31

Building B - Design criteria

5. Building B Design criteria Architectural

The following design criteria, representative of current good practice and commercial standards, form the basis of the study. Plan dimensions Planning grid

1500 × 1500mm

Partition grid

1500 × 1500mm

Structural grid

7500 × 9000mm

Vertical dimensions 3950–4235mm (see drawings) Floor to ceiling height

3200mm GF–1st Floor; 2700mm 1st–5th Floor

Raised floor

250mm

Occupancy

Structural

Density

One person per 10m2 of nett internal floor area.

Design target populations Ancillary accommodation

1,215 total.

Core areas

Include male and female toilets and cleaners’ cubicle on each floor, disabled toilets and PABX equipment on the ground floor.

Codes of practice and standards Concrete

BS 8110 Part 1: 1997 (amendments 1 & 2) - Structural use of concrete

Structural steelwork

BS 5950 Part 1: 2000 - Structural use of steelwork in buildings

Loads Imposed load Dead load Line loads

Offices: 4.0 + 1.0kN/m2 for partitions Roof: 0.75kN/m2 Self-weight plus superimposed dead load of 0.9kN/m2 External cladding Atrium glazing Internal blockwork walls

8kN/m 8kN/m 10kN/m

Deflections General

Deflections will be limited in accordance with the guidance in the appropriate Code of Practice.

Fire rating

1½hrs

Vibration

Natural frequency limited to 4Hz.

Ground conditions Bearing pressure

The ground is assumed as typical made ground to GFL –5m and clay from GFL –5m to depth. Piles are 750mm diameter open bored piles using C30/37 concrete. A pile capacity working load capacity of 1MN @ 14m penetration into the clay, varying linearly to 2MN @ 23m penetration. Maximum pile length 28m.

Lateral stability Propping

It is assumed that the ground does not have sufficient capacity to carry a ground-bearing slab and that all options would have a reinforced In-situ concrete suspended slab. In long-span options, intermediate piles are provided to reduce the span of this ground slab. Braced frame using shear walls. Propping is required for the Slimdek system during construction. No propping is required for the other steel frames.

22


02/10/2007 11:19:32

Building B - Outline specifications

Services

General

All normal services to be provided to typical contemporary commercial standards, including: heating, lighting, ventilation, lifts, hot and cold water supply, drainage, fire services, small power, provision for communications, lightning protection, etc.

Ventilation General

Air-conditioned using four-pipe fan coil system.

Outline specifications Architectural

External envelope External wall

Proprietary curtain walling system, 170mm thick overall.

Shop fronts at ground floor

Floor-to-ceiling ground-supported single glazing in aluminium grid frame, with aluminium louvre spandrel system over for ventilation of shops.

Internal atrium walls (if required for tenancy split)

Unitised curtain wall incorporating floor-to-ceiling single glazing units and aluminium clad spandrels. Individual units to be 1500 or 3000mm wide × storey height, top hung from slab edge.

Plant rooms

Proprietary curtain walling panel system.

Plant screen

Coated aluminium louvres connected to steel panels bolted to slab upstands.

Flat roofs

Inverted roof build-up with monolithic hot-applied bitumen polymer membrane, insulation and ballast.

Atrium roof

Fritted double glazed units in an aluminium grid frame.

Office areas Floors

Proprietary medium duty raised floor system, 250mm overall, and carpet.

Ceilings

500 × 500mm pre-finished fully demountable perforated tile with concealed suspension system.

External walls

Unitised curtain wall incorporating floor to ceiling double glazing units and stone clad insulated spandrels. Individual units to be 1500 or 3000mm wide × storey height top hung from slab edge. Solar shading to south and west façades in the form of external horizontal/vertical brises-soleils cantilevered off the face of the building to allow façade cleaning access.

Columns

Emulsion painted plastered concrete or painted dry-lined encased steel columns.

Skirtings


Retail space Generally left as shell finish for fit-out by tenants External walls

Floor to ceiling ground supported single glazing in aluminium grid frame, with aluminium louvre spandrel system over for ventilation. Stone panel rain screen with ventilated insulated cavity supported on groundbearing blockwork walls or grid frame.

Entrance halls/ground floor lift lobbies Floor

Carpet.

Walls


Ceilings


Skirtings


Furniture

Reception desk.

Doors

Stainless steel revolving doors.

Lift lobbies (upper floors) Floors

Carpet.

Walls


Ceilings


23


02/10/2007 11:19:32


Architectural continued..

Toilets Floor

Unglazed ceramic tiles.

Walls

Glazed ceramic tiles. Full height cubicle partitions and doors.

Ceilings


Skirtings

Ceramic tile.

Lighting

Downlighters.

WCs

Suspended WC pans with concealed cisterns.

Wash basins

Fully or semi-recessed vanity mounted hand basins with concealed UPVC pipework, polished granite top.

Urinals

White vitreous china.

Mirrors

Full height and width.

Vanity shelf

Polished granite.

Fittings

Polished stainless steel fittings, and shaving point.

Hand drying

Recessed paper towel dispensers.

Staircases Floors

Precast terrazzo (primary stair) or granolithic (secondary stair) treads and risers with non-slip nosings, with mild steel painted stringer.

Walls


Ceilings


Handrail

Polished stainless steel top and secondary rails.

Balustrade

Polished stainless steel posts.

Internal doors Doors

Hardwood veneered plywood solid core doors with overpanels and painted hardwood frames.

Ironmongery

Polished stainless steel.

Plant spaces

Structural

Enclosed

Floors: screed laid to falls. Walls/ceilings: unfinished structure/blockwork.

Open/external

Precast paving slabs and gravel ballast.

Intake room

Unfinished structure.

Substructures Foundations

Piled foundations (750mm diameter open-bored piles, maximum length 28m); intermediate piles provided for long-span options.

Slab

In-situ reinforced concrete suspended slab. Allowance made for lift pits and manholes.

Superstructures Concrete

Specification as given on partial floor plans. Plant room enclosures: steel frame (25kg/m2) supporting lightweight cladding.

Steel

Steel frames as shown on partial floor plans.

Fire

One-and-a-half-hour fire protection to all structural members apart from roof structure (no fire protection required). The building is not sprinkler-protected.

24


02/10/2007 11:19:33


Services

Air conditioning Design data

22°C dry bulb +/– 1°C. 50% RH +10%/–15% RH. 0.25 air changes per hour for office areas. Internal thermal loads: Occupants Office lighting Office small power

8W/m2 10W/m2 18W/m2

Occupancy

One person per 10m2.

Fresh air allowance

12 litres per second per person.

Supply

All offices air-conditioned by means of four-pipe fan coil system

Air handling

Roof-mounted air handling units serving all areas of the building. Chilled water generated by a central refrigeration plant.

Heating General

Low temperature hot water radiant panels. Gas fired boiler plant in the roof plant room.

Ventilation Supply

Vents incorporated within suspended ceiling. All toilet areas provided with mechanical supply and extract system.

Plumbing services Cold water

Rising main to cold water storage tank feeding central core and LTHW system. Separate drinking water system.

Hot water

Hot water from central roof mounted storage feeding core areas.

Roof drainage

Rainwater outlets connected to vertical stacks.

Foul drainage

All foul waste to discharge into Local Authority foul water drainage system.

Fire services

Hose reels.

Control systems Control

All mechanical services plant and equipment controlled by central BMS.

Electrical services Load densities

Offices: Lighting Small power Air conditioning Miscellaneous

12W/m2 15W/m2 60W/m2 10W/m2

Lighting

Generally to L2 office standard; control by switches with key switches for the emergency fittings. Emergency fittings to be self-contained.

Small power

Distribution within raised flooring via floor boxes. Cleaners’ sockets to walls and circulation spaces.

Communications

Provision within floor boxes for tenants’ installations.

Lightning

Protection system complying with BS 6651:1999.

Lift installation Design criteria

Designed to serve an overall, building population of one person per 14 m2. 15% of the design target population to be handled in a five minute period.

25


02/10/2007 11:19:34

Building B - Architectural drawings

Architectural drawings

A

B 9000

C 9000

D 9000

E 9000

F 9000

G 9000

H 9000

I 9000

7500

1

7500

2

9000

3 Full height atrium

7500

4

7500

5

6

Typical floor plan

In the structural drawings which follow, one page is dedicated to each structural option. On each page is part of a typical floor which represents the area highlighted in blue. In addition a cross-section through the floor zone accompanies each plan.

26


02/10/2007 11:19:34

Building B - Structural drawings

Structural drawings Flat Slab 325 mm RC slab

1. 2. 3. 4.

325mm concrete flat slab to upper floors and roof. Concrete class C 32/40. High-yield reinforcement. Assumed design imposed loads: Roof: 0.75kN/m2 Plant room: 7.5kN/m2 Offices: 5.0kN/m2 5. Vertical dimensions: Slab: 325mm Services zone: 600mm(1) Floor zone = 1075mm Ceiling/lighting: 150mm Floor to ceiling: 2700mm(2) Raised floor: 250mm Total: 4025mm

325

1075 Services zone

600


150

]


(1) (2)

550 x 550 (G-2) 450 x 450 (2-R)

Void

200mm R C Shear walls

9000

Toilet Zone

Stairs

increase to 750mm for GF - 1st increase to 3200mm for GF - 1st

Lobby

Lifts

Atrium

7500

550 x 550 (G-2) 450 x 450 (2-R)

7500

550 x 550 (G-2) 450 x 450 (2-R)

550 x 550 (G-2) 450 x 450 (2-R)

550 x 550 (G-2) 450 x 450 (2-R)

550 x 550 (G-2) 450 x 450 (2-R)


9000

9000

9000

9000

27


02/10/2007 11:19:36


PT Flat Slab

250mm Post-tensioned slab

Reinforcement

250

PT duct 1000

Services zone

600


150


1. 2. 3. 4.

250mm post-tensioned concrete flat slab to upper floors and roof. Concrete class C 32/40. High-yield reinforcement. Post-tensioning: Each post-tensioning tendon has five No. 12.7 mm diameter strands. 5. Assumed design imposed loads: Roof: 0.75 kN/m2 Plant room: 7.5kN/m2 Offices: 5.0kN/m2 6. Vertical dimensions: Slab: 250mm Services zone: 600mm(1) Floor zone = 1000mm Ceiling/lighting: 150mm Floor to ceiling: 2700mm (2) Raised floor: 250mm Total: 3950mm

]

(1) (2)

Toilet Zone

9000

Void


Lobby

Lifts

Atrium

7500

7500

Stairs


All Columns 500 x 500 (G-1) 450 x 450 (1-R)

9000

9000

9000

9000

28


02/10/2007 11:19:37


Composite

130

457 x 191 UB67 800 (min)

1.2mm ribdeck AL Services zone

1087

350 (min)


150

]


(1)

including downstand beams increase to 950mm for GF - 1st increase to 3200mm for GF - 1st

(2) (3)

406 x 140 UB46 Toilet Zone

406 x 140 UB39

406 x 140 UB39

406 x 140 UB46

406 x 140 UB39

9000

406 x 140 UB39 9000

C3 = 356 x 368 UC129

C2

406 x 140 UB39 9000

406 x 140 UB46

406 x 140 UB46

C2

406 x 140 UB39

C2

457 x 191 UB67

406 x 140 UB46

C3

406 x 140 UB46

406 x 140 UB46

406 x 140 UB46

C2

457 x 191 UB67

406 x 140 UB46

C3

406 x 140 UB46

406 x 140 UB46

C2

457 x 191 UB67

457 x 191 UB67

406 x 140 UB46

C3

406 x 140 UB46

406 x 140 UB46

C2 = 305 x 305 UC97 Atrium

254 x 146 UB31

406 x 140 UB39

457 x 191 UB67

406 x 140 UB46

406 x 140 UB46

Lifts

C1 = 254 x 254 UC73

406 x 140 UB46

C3

457 x 191 UB67

406 x 140 UB46

7500 7500

C1

254 x 146 UB31

254 x 146 UB31

C2

C2

254 x 146 UB31

Stairs

C2

406 x 140 UB46

Lobby

457 x 191 UB67

406 x 140 UB39

457 x 191 UB67

457 x 191 UB67

9000

Void

C2

406 x 140 UB39


406 x 140 UB46

C3

254 x 146 UB31

406 x 140 UB46

C2

C3

457 x 191 UB67

A193 mesh

1. 130mm lightweight concrete slab on 1.2mm Ribdeck AL on steel frame to upper floors and roof. 2. Lightweight concrete class C 32/40. 3. Steel grade S355. 4. Assumed design imposed loads: Roof: 0.75kN/m2 Plant room: 7.5kN/m2 Offices: 5.0kN/m2 5. Vertical dimensions: Slab: 130mm (1) Services zone : 807mm(2) Floor zone = 1087mm Ceiling/lighting: 150mm ≈ 1090mm Floor to ceiling: 2700mm(3) Raised floor: 250mm Total: 4040mm

C2

9000

29


02/10/2007 11:19:37


A142 mesh in 50mm (min) structural topping

150mm hollowcore

Typical edge beam 50

200

250

450 600 600 Services zone

In-situ + Hollowcore 1. 150mm precast concrete hollowcore units with 50mm (min) mesh reinforced structural topping to upper floors and roof. In-situ reinforced concrete beams and columns. 2. Concrete class C 32/40. 3. High-yield reinforcement. 4. Assumed design imposed loads: Roof: 0.75kN/m2 Plant room: 7.5kN/m2 Offices: 5.0kN/m2 5. Vertical dimensions : Slab and topping: 200mm Services zone(1): 800mm(2) Floor zone = 1150mm Ceiling/lighting: 150mm Floor to ceiling: 2700mm (3) Raised floor: 250mm Total: 4100mm

425 600

450

1150

800 (min)

600

350(min) 150


]

(1)


(2) (3)

A

A

A

Void B

B


A

Lobby

A 600 x 600 R C Beam

B

B

B

B 600 x 250 R C Beam

9000

C Stairs A

A

B

7500

7500

B

Beam Schedule

C 600 x 425 R C Beam

Lifts

A

Atrium

Toilet Zone

B

B

B

A

A

A

A

A

A

A

A

A

A

A

B

B

All Columns 450 x 450

A

9000

9000

9000

9000

30


02/10/2007 11:19:38


PT Band Beams

225

2500 (typical) PT Duct

Services zone

325 800 1175 (min) 350 (min)


150


1. 225mm post-tensioned concrete flat slab with band beams to upper floors and roof. 2. Concrete class C 32/40. 3. High-yield reinforcement. 4. Post-tensioning: Each post-tensioning tendon has five No. 12.7 mm diameter strands. 5. Assumed design imposed loads: Roof: 0.75kN/m2 Plant room: 7.5kN/m2 Offices: 5.0kN/m2 6. Vertical dimensions: Slab: 225mm (1) Services zone : 800mm(2) Floor zone = 1175mm Ceiling/lighting: 150mm Floor to ceiling: 2700mm (3) Raised floor: 250mm Total: 4125mm

]

(1) (2) (3)

Toilet Zone

7500

7500

9000

Void



Stairs

550 x 1750 P T edge beam

550 x 2750 P T beam

Lobby

Lifts

Atrium

550 x 2500 P T Beam (typical)

All Columns 800 x 800

9000

9000

9000

9000

31


02/10/2007 11:19:39


Long-Span Composite

130

1. 130mm lightweight concrete slab on 1.2mm Ribdeck AL on steel frame to upper floors and roof. Steel columns and cellular beams. 2. Lightweight concrete class C 32/40. 3. Steel grade S355. 4. Assumed design imposed loads: Roof: 0.75kN/m2 Plant room: 7.5kN/m2 Offices: 5.0kN/m2 5. Vertical dimensions: Slab and decking: 130mm (1) Services zone : 800mm(2) Floor zone = 1080mm Ceiling/lighting: 150mm Floor to ceiling: 2700mm (3) Raised floor: 250mm Total: 4030mm

1.2 mm ribdeck AL

A142 mesh

Cellular beam 457 x 191 UB67 + 533 x 210 UB92

710 (Typical)

800 1080 (min)

Services zone Ceiling and lighting zone

150


]

(1) (2) (3)

Lifts

406 x 140 UB39

406 x 140 UB39

406 x 140 UB39

406 x 140 UB39

406 x 140 UB39

406 x 140 UB39

406 x 140 UB39

406 x 140 UB39

9000

Lobby

Stairs Toilet Zone

C3

C3


Void

533 x 210 UB82

610 x 229 UB101

610 x 229 UB101

C4

406 x 140 UB39

610 x 229 UB101

C3


Atrium

C1 = 254 x 254 UC73 C2 = 305 x 305 UC97 610 x 229 UB101

610 x 229 UB101

533 x 210 UB82 610 x 229 UB101

C4

C3

C3

C3

C3 = 356 x 368 UC129

C2

533 x 210 UB82 9000

C3

533 x 210 UB82 9000

C3

533 x 210 UB82 9000

C3

533 x 210 UB82

457 x 191 UB67 + 533 x 210 UB92

457 x 191 UB67 + 533 x 210 UB92

457 x 191 UB67 + 533 x 210 UB92

457 x 191 UB67 + 533 x 210 UB92

457 x 191 UB67 + 533 x 210 UB92

457 x 191 UB67 + 533 x 210 UB92

457 x 191 UB67 + 533 x 210 UB92

457 x 191 UB67 + 533 x 210 UB92

457 x 191 UB67 + 533 x 210 UB92

457 x 191 UB67 + 533 x 210 UB92

457 x 191 UB67 + 533 x 210 UB92

356 x 127 UB33

7500

C1

457 x 191 UB67 + 533 x 210 UB92

356 x 127 UB33

7500

C4 = 356 x 368 UC177

C3

9000

32


02/10/2007 11:19:40


A142 mesh in 50 mm (min) structural topping

Steel + Hollowcore 1. 200mm precast concrete hollowcore units with 50mm (min) mesh reinforced structural topping on steel frame to upper floors and roof. 2. Concrete class C 32/40. 3. Steel grade S355. 4. Assumed design imposed loads: Roof: 0.75kN/m2 Plant room: 7.5kN/m2 Offices: 5.0kN/m2 5. Vertical dimensions: Slab: 250mm Services zone(1): 883mm(2) Floor zone = 1283mm Ceiling/lighting: 150mm ≈ 1285mm Floor to ceiling: 2700mm (3) Raised floor: 250mm Total: 4235mm

250

200 mm Hollowcore

533 x 210 UB82

1283 800 (min)

Services zone

350 (min)

]

150


(1) (2) (3)


C1 = 305 x 305 UC97 200mm R C Shear walls

Lobby

Stairs

406 x 178 UB54

Toilet Zone

305 x 165 UB40 Lifts

203 x 133 UB25

C3

9000

457 x 191 UB67 9000

Atrium

457 x 191 UB67

533 x 210 UB82

533 x 210 UB82 203 x 133 UB25 C3

457 x 191 UB67 9000

C3

C2

C2

203 x 133 UB25 C3

C4 = 356 x 368 UC153

C3

C2

533 x 210 UB82 203 x 133 UB25

7500 406 x 140 UB39

406 x 140 UB46

457 x 191 UB67

C3 = 356 x 368 UC129

406 x 178 UB54

C2

533 x 210 UB82

C1

457 x 191 UB67 203 x 133 UB25

C4

C2 = 305 x 305 UC158

203 x 133 UB25

457 x 191 UB82

406 x 140 UB46

7500 406 x 140 UB39

C3

254 x 146 UB31

C3

203 x 133 UB25

406 x 178 UB54

457 x 191 UB67

203 x 133 UB25

533 x 210 UB82

457 x 191 UB67

Void

406 x 178 UB60

C4

533 x 210 UB101

533 x 210 UB101

9000

406 x 178 UB60

C3

C3

406 x 178 UB54

457 x 191 UB67

457 x 191 UB67

457 x 191 UB82

C3

457 x 191 UB67

C3

9000

33


02/10/2007 11:19:41


Slimdek

In situ concrete slab

1. 342mm (overall) concrete slab on SD225 deep decking on asymmetric steel beams to upper floors and roof. 2. Concrete class C 32/40. 3. Steel grade S355. 4. Assumed design imposed loads: Roof: 0.75kN/m2 Plant room: 7.5kN/m2 Offices: 5.0kN/m2 5. Vertical dimensions: Slab: 342mm Services zone: 600mm(1) Floor zone = 1092mm Ceiling/lighting: 150mm ≈ 1095mm Floor to ceiling: 2700mm (2) Raised floor: 250mm Total: 4045mm

342 300 ASB 249 1092 600

Services zone

150


]


(1)


(2)

C2

300 ASB196

300 ASB153

C1

280 ASB124 200mm R C Shear walls

300 ASB155

300 ASB155

300 ASB249

300 ASB249

9000

Void

Lobby

280 ASB74 280 ASB74

280 ASB74

C2

Stairs

Toilet Zone

300 ASB249

C1

300 ASB155

A193 mesh SD225 Deep decking

Atrium C1 = 305 x 305 UC97 C2 = 356 x 368 UC129

280 ASB74 Lift

300 ASB153 280 ASB124

C1

300 ASB249

300 ASB249

9000

9000

300 ASB249

C1

C2

300 ASB249

C2

300 ASB249

C2

C2

300 ASB249

C2

300 ASB249

C2

203 x 102 UB23

C2

C1

203 x 102 UB23

203 x 102 UB23

300 ASB249

203 x 102 UB23

C2

203 x 102 UB23

300 ASB249

280 ASB74

C2

7500

203 x 102 UB23

280 ASB74

7500

C2

203 x 102 UB23

300 ASB196

9000

203 x 102 UB23

C2

9000

34


02/10/2007 11:19:42

Programmes

6. Programmes A comparison of the overall programme durations, showing each of the periods from procurement to completion, is given in tabular and graphical form in this Chapter. Detailed programmes for the Flat Slab and Composite options for both Building A and Building B are also presented in Appendix A – Detailed programmes. Structural option

Procurement Lead time Overall Frame time (weeks) (weeks) construction construction time (weeks) time (weeks)

Overall project time (weeks)

Building A Flat Slab

10

4

50

10

64

PT Flat Slab

10

4

51

11

65


10

4

52

13

66

Composite

10

12

48

8

70

Steel + Hollowcore

10

12

48

7

70

Slimdek

10

12

48

7

70

PT Flat Slab

10

6

66

17

82

Flat Slab

10

6

67

18

83

Building B

Note Frame construction time for Composite, Steel + Hollowcore, Slimdek and Long-Span Composite options includes construction of concrete jump-form core.

Procurement programme

Lead times

PT Band Beams

10

7

66

17

83


10

6

70

22

86

Steel + Hollowcore

10

16

65

21

91

Slimdek

10

16

65

21

91

Composite

10

16

67

23

93

Long-Span Composite

10

18

67

23

95

The procurement element is identical for each option at ten weeks, comprising two weeks for collation of information, four weeks for bidding, three weeks for bid evaluation and one week for award of contract, assuming a traditional approach to works package subcontracting.

Building A The lead time for the Flat Slab, In-situ + Hollowcore and PT Flat Slab options is four weeks, comprising one week for working drawings, one week for drawing approval, one week for material procurement and one week for mobilisation.

35


02/10/2007 11:19:43

Programmes

The lead time for the structural frame for the Composite, Steel + Hollowcore and Slimdek options is 12 weeks, comprising four weeks for working drawings, one week for drawing approval, one week for material procurement, five weeks for manufacture and one week for mobilisation.

Building B The lead time for the structural frame for the Flat Slab, In-situ + Hollowcore and PT Flat Slab options for the short-span options is six weeks, comprising one week for working drawings, one week for drawing approval, two weeks for material procurement and two weeks for mobilisation. For the long-span PT Band Beam option, an extra week is required for procurement, increasing the lead time to seven weeks. The lead time for the structural frame for the Composite, Steel + Hollowcore and Slimdek options for the short-span options is 16 weeks, comprising four weeks for working drawings, one week for drawing approval, two weeks for material procurement, eight weeks for manufacture and one week for mobilisation. For the Long-Span Composite option, an extra two weeks are required for manufacture, increasing the lead time to 18 weeks.

Other elements With regard to lead times, the most critical element is cladding, which is required relatively early in the construction and for which the lead time can be as much as 45 weeks for complex, high-quality curtain walling systems. Clearly, it would be unlikely that incurring such a long lead time after contract award would be a viable option on most projects. Accordingly, the procurement process for cladding would generally need to be set in motion before contract award and several solutions are available to overcome this problem. It is possible for a client to enter into a framework agreement with one or more cladding manufacturers, under which production space can be reserved to suit an anticipated project schedule. This route is most likely to be adopted by an experienced client with an ongoing stream of developments. Alternatively, a client may pre-order the cladding prior to awarding a contract, in order to guarantee delivery to suit an eventual construction programme. In either case, the client bears the financial risk of such a commitment to the cladding manufacturer. The early appointment of a contractor under a two-stage tender approach can prove effective in overcoming the problem and may also prove beneficial by involving the contractor’s expertise in buildability and programming in the cladding procurement. Alternatively, a long-term partnering or alliancing approach can alleviate the difficulty; however, the risk apportionment on such a basis needs to be appropriate to the project and must be fully understood and carefully considered by all parties. Lifts and some M&E plant also tend to have long lead times, especially non-standard equipment, but as these are generally required later in the project, greater scope exists for managing the risks associated with pre-ordering.

36


02/10/2007 11:19:44

Programmes

Construction programmes

Assumptions and logic A five-day week was assumed. Holidays have not been shown on the programme and no allowance has been made for inclement weather. A simplified view has been taken of such factors as logistics, site access, boundary constraints, cranage, etc., where it has been assumed that there would be no access or supply problems. These aspects are highly sitespecific and could result in shorter or longer construction periods. On activities not related to the structure, similar resources and sequences have been assumed for all the options. It was assumed that the ground floor slab would be fully or substantially complete before a steel frame is erected. Whilst it is possible for steelwork to be erected from the pile caps before the ground floor slab is constructed, thus saving time on the critical path, many steelwork contractors prefer the ground floor slab to be installed, as it is safer for the steelwork erectors to work from mobile elevated working platforms positioned on a flat surface, as well as providing a clear lay-down area for the steelwork. It is also possible for a concrete frame to be built before the ground floor slab is constructed, the columns being cast from pile caps and the ground floor slab being installed subsequently. The time savings are similar for both materials. It was assumed that the frame for Building A would be erected using a mobile crane and that one tower crane is used for the erection of Building B. It was also assumed that longlead items such as cladding, lifts and some plant would be pre-ordered. With the Flat Slab, PT Flat Slab and Slimdek options, although the availability of a clear unimpeded soffit would permit greater use of prefabrication in the M&E services distribution, with consequent programme savings, no allowance has been made for any reduction in the construction programme as a result of this potential benefit.

Building A The construction programmes range from 50 to 52 weeks for the buildings constructed using the Flat Slab, In-situ + Hollowcore and PT Flat Slab options, compared with a 48week period for each of the buildings constructed using the Composite, Steel + Hollowcore and Slimdek options.

Building B Of the short-span buildings, construction programmes range from 65 weeks for the Steel + Hollowcore and Slimdek options, the PT Flat Slab option at 66 weeks, closely followed by the Flat Slab and Composite options at 67 weeks, with the In-situ + Hollowcore option at 70 weeks. The construction programmes for the long-span options are almost identical, with the PT Band Beam option being marginally shorter at 66 weeks, compared to 67 weeks for the Long-Span Composite option.

37


02/10/2007 11:19:44

Building A - Programmes


Building A

Composite — 48 weeks 0

10

20

0

10

20

30

40

50

60

30

40

50

60

30

40

50

60

30

40

50

60

Activity Number of weeks Establish site 2 Substructures 8 Superstructure 8 Roof finishes 8 11 Roof installations External envelope 13 Cores and risers 13 Toilet fit-out 16 8 M & E first fix M & E second fix 5 Lifts 12 Fit-out first floor 9 Fit-out second floor 8 5 Fit-out ground floor Final fix 9 Testing & commissioning 17 External works 12

Week number

Steel + Hollowcore — 48 weeks 0

10

20

0

10

20


Week number

38


02/10/2007 11:19:45


Slimdek — 48 weeks 0

10

20

0

10

20

30

40

50

60

30

40

50

60

30

40

50

60

30

40

50

60


Week number

Flat Slab — 50 weeks 0

10

20

0

10

20


Week number

39


02/10/2007 11:19:46


PT Flat Slab — 51 weeks 0

10

20

0

10

20

30

40

50

60

30

40

50

60

30

40

50

60

30

40

50

60


Week number

In-Situ + Hollowcore — 52 weeks 0

10

20

0

10

20


Week number

40


02/10/2007 11:19:48

Building B - Programmes


Building B

Steel + Hollowcore — 65 weeks 0

10

20

30

40

50

60

70

0

10

20

30

40

50

60

70

Activity Number of weeks Establish site 2 Substructures 15 Superstructure 21 Roof finishes 9 Roof installations 15 Atrium glazing 19 External envelope 15 Cores and risers 18 Toilet fit-out 20 14 M & E first fix M & E second fix 10 Lifts 22 Fit-out first floor 10 10 Fit-out second floor 10 Fit-out third floor 10 Fit-out fourth floor 10 Fit-out fifth floor 12 Final fix Testing & commissioning 17 External works 12

Week number

Slimdek — 65 weeks 0

10

20

30

40

50

60

70

0

10

20

30

40

50

60

70


Week number

41


02/10/2007 11:19:49


PT Flat Slab — 66 weeks 0

10

20

30

40

50

60

70

0

10

20

30

40

50

60

70


Week number

PT Band Beams — 66 weeks 0

10

20

30

40

50

60

70

0

10

20

30

40

50

60

70


Week number

42


02/10/2007 11:19:50


Flat Slab — 67 weeks 0

10

20

30

40

50

60

70

0

10

20

30

40

50

60

70


Week number

Composite — 67 weeks 0

10

20

30

40

50

60

70

0

10

20

30

40

50

60

70


Week number

43


02/10/2007 11:19:51


Long-Span Composite — 67 weeks 0

10

20

30

40

50

60

70

0

10

20

30

40

50

60

70


Week number

In-Situ + Hollowcore — 70 weeks 0

10

20

30

40

50

60

70

0

10

20

30

40

50

60

70


Week number

44


02/10/2007 11:19:53

Summary of costs

7. Summary of costs Costs

Basis of pricing Prices used in this study have been prepared by Davis Langdon, based on pricing data obtained in June 2006 from their national cost database of recently tendered projects. Rates for Building A are based on construction in south east England and rates for Building B are based on construction in central London.

Preliminaries The cost of the main contractor’s preliminaries for each option was based on two separate elements. A lump sum was included to allow both for non-work-related aspects such as contractual requirements for insurances, employer’s facilities, etc. and for fixed one-off costs such as site establishment, access roads, crane bases, services connection charges, etc. Separate allowances were made for time-related costs, such as management and staff, site accommodation, services and facilities, cranage, etc. Such costs vary according to programme duration and the sequencing of operations within the programme. Adjustment of these costs has been made to reflect the different construction durations identified in the programmes produced by Mace. For Building A, preliminaries on average equate to an on-cost of 13.6% of the basic construction cost and for Building B, preliminaries on average equate to an on-cost of 15.5% of the basic construction cost.

Finance and rental costs The study did not include assessment of the costs of financing the project, nor consideration of return on rentals.

Summary tables The itemised costs for Building A and Building B are presented in the following tables, followed by the key rates used in the study.

45


02/10/2007 11:19:54

Summary of costs - Building A

Building A 4642 m2 GIFA Element

Short-span options Flat Slab

Composite


PT Flat Slab

Steel + Hollowcore

Slimdek

Element total (£)

Element total (£)

Element total (£)

Element total (£)

Element total (£)

Element total (£)

Substructure

199,480

189,765

202,641

200,512

195,452

192,107

Frame/upper floors

564,827

568,078

591,645

642,599

643,704

872,208

Roof finishes

241,208

241,208

241,208

241,208

241,208

241,208

63,000

63,000

63,000

63,000

63,000

63,000

External cladding

1,166,600

1,174,480

1,187,720

1,154,800

1,199,980

1,175,460

Internal planning

141,230

154,110

145,255

139,740

156,630

153,900

Wall finishes

51,010

50,040

49,684

48,820

52,240

50,240

Floor finishes

274,432

274,432

274,432

274,432

274,432

274,432

Ceiling finishes

125,308

125,308

125,308

125,308

125,308

125,308

Fittings

60,000

60,000

60,000

60,000

60,000

60,000

Sanitary

208,890

208,890

208,890

208,890

208,890

208,890

1,285,834

1,311,551

1,285,834

1,285,834

1,311,551

1,285,834

637,811

650,567

637,811

637,811

650,567

637,811

70,000

70,000

70,000

70,000

70,000

70,000

BWIC

172,470

172,470

172,470

172,470

172,470

172,470

Contingency

394,658

398,542

398,692

399,407

406,907

418,715

Preliminaries

735,000

715,000

755,000

745,000

715,000

715,000

Overheads and profit

383,505

385,646

388,175

388,190

392,840

402,995

£6,775,263

£6,813,088

£6,857,765

£6,858,021

£6,940,180

£7,119,578

Stairs

Mechanical Electrical Lifts

TOTAL

Element


£/m2 Substructure Frame/upper floors

Composite

%

£/m2


%

£/m2

%

PT Flat Slab

£/m2

%

Steel + Hollowcore

£/m2

%

Slimdek

£/m2

%

43

2.9

41

2.8

44

3.0

43

2.9

42

2.8

41

2.7

122

8.3

122

8.3

127

8.6

138

9.4

139

9.3

188

12.3

Roof finishes

52

3.6

52

3.5

52

3.5

52

3.5

52

3.5

52

3.4

Stairs

14

0.9

14

0.9

14

0.9

14

0.9

14

0.9

14

0.9

External cladding

252

17.2

253

17.2

256

17.3

249

16.8

258

17.3

253

16.5

Internal planning

30

2.1

33

2.3

31

2.1

30

2.0

34

2.3

33

2.2

Wall finishes

11

0.8

11

0.7

11

0.7

11

0.7

11

0.8

11

0.7

Floor finishes

59

4.1

59

4.0

59

4.0

59

4.0

59

4.0

59

3.9

Ceiling finishes

27

1.8

27

1.8

27

1.8

27

1.8

27

1.8

27

1.8

Fittings

13

0.9

13

0.9

13

0.9

13

0.9

13

0.9

13

0.8

45

3.1

45

3.1

45

3.0

45

3.0

45

3.0

45

2.9

Mechanical

277

19.0

283

19.3

277

18.8

277

18.7

283

18.9

277

18.1

Electrical

Sanitary

137

9.4

140

9.5

137

9.3

137

9.3

140

9.4

137

9.0

Lifts

15

1.0

15

1.0

15

1.0

15

1.0

15

1.0

15

1.0

BWIC

37

2.5

37

2.5

37

2.5

37

2.5

37

2.5

37

2.4

Contingency

85

5.8

86

5.8

86

5.8

86

5.8

88

5.9

90

5.9

Preliminaries

158

10.8

154

10.5

162

11.0

160

10.9

154

10.3

154

10.0

83

5.7

83

5.7

84

5.7

84

5.7

84

5.7

88

5.7

Overheads and profit TOTAL

£1,460

£1,468

£1,477

£1,477

£1,495

£1,534

46


02/10/2007 11:19:54

Summary of costs - Building B

Building B 16,480 m2 GIFA Element


PT Flat Slab

Long-span options

Composite

Element total Element total Element total (£) (£) (£)

Short-span options


PT Band Beams

Long-Span Composite

Steel + Hollowcore

Slimdek

Element total (£)

Element total (£)

Element total (£)

Element total (£)

Element total (£)

891,672

865,937

815,468

885,169

907,622

848,868

860,967

852,231

1,811,939

2,016,344

1,878,457

1,846,453

2,227,681

2,201,664

2,275,704

3,011,992

Roof finishes

545,080

545,080

545,080

545,080

545,080

545,080

545,080

545,080

Stairs

132,000

132,000

132,000

132,000

132,000

132,000

132,000

132,000

External cladding

5,951,060

5,849,590

5,957,935

6,053,840

6,086,885

5,957,935

6,208,265

5,974,270

Internal planning

297,080

293,790

355,728

300,225

301,360

355,638

366,552

356,352

Wall finishes

234,455

229,931

256,770

233,226

227,825

241,566

264,162

263,112

Floor finishes

1,167,221

1,167,221

1,167,221

1,167,221

1,167,221

1,167,221

1,167,221

1,167,221

Ceiling finishes

702,366

702,366

702,366

702,366

702,366

702,366

702,366

702,366

Fittings

132,500

132,500

132,500

132,500

132,500

132,500

132,500

132,500

Sanitary

824,000

824,000

824,000

824,000

824,000

824,000

824,000

824,000

Mechanical

4,544,360

4,544,360

4,635,247

4,544,360

4,544,360

4,635,247

4,635,247

4,544,360

Electrical

2,690,688

2,690,688

2,739,502

2,690,688

2,690,688

2,739,502

2,739,502

2,690,688

600,000

600,000

600,000

600,000

600,000

600,000

600,000

600,000

Substructure Superstructure

Lifts

601,800

601,800

601,800

601,800

601,800

601,800

601,800

601,800

Contingency

1,584,467

1,589,670

1,600,806

1,594,420

1,626,854

1,626,404

1,654,152

1,679,848

Preliminaries

3,350,000

3,310,000

3,350,000

3,470,000

3,310,000

3,350,000

3,270,000

3,270,000


1,563,641

1,565,717

1,577,693

1,579,401

1,597,694

1,599,707

1,618,771

1,640,869

£27,624,328

£27,660,993

£27,872,572

£27,902,748

£28,225,936

£28,261,499

£28,598,289

£28,998,690

BWIC

TOTAL

Element


Long-span options

PT Flat Slab

Composite


£/m2

£/m2

PT Band Beams

Short-span options

Long-Span Composite

Steel + Hollowcore

£/m2

%

£/m2

%

Slimdek

£/m2

%

£/m2

%

54

3.2

53

3.1

49

2.9

110

6.6

122

7.2

114

33

2.0

33

2.0

8

0.5

8

0.5

External cladding

361

21.5

355

21.0

Internal planning

18

1.1

18

1.1

22

1.3

18

1.1

18

1.1

22

1.3

22

1.3

22

1.2

Wall finishes

14

0.8

14

0.8

16

0.9

14

0.8

14

0.8

15

0.9

16

0.9

16

0.9

Floor finishes

71

4.2

71

4.2

71

4.2

71

4.2

71

4.1

71

4.1

71

4.1

71

4.0

Ceiling finishes

43

2.5

43

2.5

43

2.5

43

2.5

43

2.5

43

2.5

43

2.4

43

2.4

Fittings

8

0.5

8

0.5

8

0.5

8

0.5

8

0.5

8

0.5

8

0.5

8

0.5

Sanitary

50

3.0

50

3.0

50

2.9

50

2.9

50

2.9

50

2.9

50

2.9

50

2.8

Mechanical

276

16.5

276

16.3

281

16.5

276

16.2

276

16.0

281

16.3

281

16.1

276

15.6

Electrical

163

9.7

163

9.7

166

9.8

163

9.6

163

9.5

166

9.6

166

9.5

163

9.2

Lifts

36

2.2

36

2.2

36

2.1

36

2.1

36

2.1

36

2.1

36

2.1

36

2.1

BWIC

37

2.2

37

2.2

37

2.1

37

2.1

37

2.1

37

2.1

37

2.1

37

2.1

Contingency

96

5.7

96

5.7

97

5.7

97

5.7

99

5.7

97

5.7

100

5.8

101

5.8

Preliminaries

203

12.1

201

11.9

203

12.0

211

12.4

201

11.7

203

11.8

199

11.4

198

11.2

95

5.7

94

5.7

95

5.7

95

5.7

97

5.7

97

5.7

98

5.7

99

5.7

Substructure Superstructure Roof finishes Stairs

Overheads and profit TOTAL

£1,676

£1,678

%

£/m2

%

54

3.2

55

3.2

52

3.0

52

3.0

52

2.9

6.7

112

6.6

135

7.9

134

7.7

138

7.9

183

10.3

33

1.9

33

1.9

33

1.9

33

1.9

33

1.9

33

1.9

8

0.5

8

0.5

8

0.5

8

0.5

8

0.5

8

0.5

362

21.3

367

21.6

369

21.5

362

21.0

377

21.6

363

20.5

£1,691

%

£1,693

£1,713

£1,715

£1,735

£/m2

%

£1,759

47


02/10/2007 11:19:55

Summary of costs

Key rates Key rates used in the structural elements of the study are tabulated below: Building element

Unit

Building A

Building B

Concrete in walls

m3

£125

£125

Concrete in suspended slabs

m3

£115

£120

Lightweight concrete in suspended slabs

m3

£145

£145

Concrete in beams

m3

£115

£120

Concrete in columns

m3

£115

£120

A142 mesh reinforcement

m2

£3

£3

A193 mesh reinforcement

m2

£4

£4

Reinforcement in suspended slabs

tonne

£820

£840

Reinforcement in beams

tonne

£820

£840

Reinforcement in walls

tonne

£820

£840

Reinforcement in columns

tonne

£820

£840

Post-tensioning to floor slabs

m2

£27

£27

Intumescent coating - 60 minute (site applied)

m2

£13

–

Intumescent coating - 90 minute (site applied)

m2

–

£20

Formwork to walls

m2

£32

£31

Formwork to soffits of suspended slabs

m2

£31

£32

Formwork to beams

m2

£42

£42

Formwork to columns

m2

£42

£42

Formwork to columns - curved

m2

£63

–

150mm hollowcore planks

m2

£46

£47

200mm hollowcore planks

m2

£48

£54

Solid grade S355 steel beams

tonne

£1,390

£1,405

Solid grade S355 steel columns

tonne

£1,390

£1,405

Solid grade S355 steel columns hollow sections

tonne

£1,730

–

ASB grade S355 steel beams

tonne

£1,590

£1,600

Cellular grade S355 steel beams

tonne

Core walls SHS steel bracing

tonne

–

£1,545

£1,770

–

Ribdeck AL 1.2mm steel decking

m2

£21

£21

SD225 steel decking (propped)

m2

£36

£39

Shear studs -19mm × 100mm

No

£1

£1

Shear studs -19mm × 120mm

No

£1

£1

Building A

Building B

Key rates used in other elements of the study are tabulated below: Other element

Unit

External cladding Curtain walling

m2

£360

£830

Rain-screen

m2

£260

£935

Brise-soleil

m2

£310

£310

Atrium walling

m2

£360

£480

Shop fronts

m2

–

£470

Non-structural dry-lined metal stud partitions

m2

£55

£65

Blockwork walls to retail units

m2

–

£80

Internal planning

48


02/10/2007 11:19:56

Study findings

8. Study findings Costs

Building A – 3 storey In terms of overall construction cost for Building A, the most economic option, the Flat Slab, was found to be between 0.6% and 4.8% less expensive than the alternative structural solutions.

Building B – 6 storey In terms of overall construction cost for Building B, for the short-span situation, the most economic option, the Flat Slab, was found to be between 0.1% and 4.7% less expensive than the alternative structural solutions.

Overall The most significant differential for both buildings occurred using the Slimdek option, for which the overall construction costs were found to be between 5.0% and 5.1% more expensive than the most economic option, after adjusting time-related preliminaries for construction programme difference. When only the costs of the structural frame and upper floors are considered, the Slimdek option was found to be between 54.1% and 66.4% more expensive than the most economic option.

Programme

Building A With regard to speed of construction, for Building A the construction programmes for the Composite, Steel + Hollowcore and Slimdek options are all identical at 48 weeks, with 50 weeks required for the Flat Slab option, 51 weeks for the PT Flat Slab option and 52 weeks for the In-situ + Hollowcore option.

Building B With regard to speed of construction, for the short-span options in Building B, the construction programmes for both the Steel + Hollowcore and Slimdek options are identical at 65 weeks, with 66 weeks required for the PT Flat Slab option; the Flat Slab option and Composite options identical at 67 weeks and 70 weeks for the In-situ + Hollowcore option. For the long-span options in Building B, the PT Band Beam option was found to have a programme of 66 weeks, compared to a programme of 67 weeks for the Long-Span Composite option. When considering a ten week procurement time and a lead time of 4-7 weeks for the Flat Slab, In-situ + Hollowcore, PT Flat Slab and PT Band Beam options; and, 12–18 weeks for the Composite, Steel + Hollowcore, Slimdek and Long-Span Composite options; the overall programmes are as summarised below:

49


02/10/2007 11:19:57

Study findings

Building A – short-span

Building B – short-span

Building B – long-span

Flat Slab

64 weeks PT Flat Slab

82 weeks PT Band Beams

PT Flat Slab

65 weeks Flat Slab

83 weeks Long-Span Composite 95 weeks

83 weeks

In-situ + Hollowcore 66 weeks In-situ + Hollowcore 86 weeks Composite

70 weeks Steel + Hollowcore

91 weeks

Steel + Hollowcore

70 weeks Slimdek

91 weeks

Slimdek

70 weeks Composite

93 weeks

The study findings are presented in the following manner: The costings are divided into the following eight primary components which together make up the overall cost of each scheme design: Substructures Frames and upper floors Cladding Internal planning Roof finishes and internal finishes Mechanical and electrical services Preliminaries Contingency and overheads and profit. For each component, the costs per m2 of gross internal floor area for each of the eight options are compared graphically and in tabular form, with the most economical option for that component being used as the base for comparison. The costs of each primary component are also broken down where appropriate; for example ‘frames and upper floor costs’ are sub-divided into concrete frame, formwork and reinforcement, steel frame, decking & slabs and fire protection. (Minor differences between the figures used in the Study findings and the Summary of costs are due to rounding.)

Average Elemental Breakdown

Average Elemental Breakdown

Internal Planning 2%

M&E, Lifts & BWIC 34%

Substructure 3%

Frame and Upper Floors 10%

Building A

Roof Finishes & Internal Finishes 11% Preliminaries 11%

Internal Planning 1%

External Cladding 17%

M&E, Lifts & BWIC 34%

Substructure 3%

Frame and Upper Floors 8%

Contingency & O/h&P 12%

External Cladding 21%

Roof Finishes & Internal Finishes 10% Preliminaries 12%

Contingency & O/h&P 11%

Building B

50


05/10/2007 09:47:59

Study findings - Building A

Study findings – Building A

Overall costs Based on the building footprints and outline specifications compiled by Allies and Morrison, together with the structural design information and calculation provided by Arup, all six structural options are within 5.1% of each other, after adjusting time-related preliminaries for construction programme differences. Of particular note is the significance of M&E services costs in the overall comparison, representing an average of 34% of total costs, and of the external cladding, representing an average of 17% of total costs. As illustrated in the figure and table, the Slimdek option was found to be 5.1% more expensive than the Flat Slab option, with both options providing clear, unimpeded soffits. These figures are based on cost per m2 of gross internal area. The differences in cost would be even greater if net internal areas had been considered, due to the larger area taken up by a steel core. However, as this level of detail would not normally be apparent at outline design stage, it has not been examined further in this study.

1525 1500 1475 1450

Slimdek

Steel + Hollowcore

Composite

Flat Slab

1400

PT Flat Slab

1425


Overall construction costs

£/m² 1550

Overall costs £/m2

% difference

Flat Slab

£1,460

-

Composite

£1,468

+0.5%


£1,477

+1.2%

PT Flat Slab

£1,477

+1.2%

Steel + Hollowcore

£1,495

+2.4%

Slimdek

£1,534

+5.1%

In Table 1 and Table 2 which follow, showing the construction costs for each element of the building, the % comparison is related to the cost for the most economic option for the element in question.

51


02/10/2007 11:19:59


Table 1 Element

Elemental cost comparison. Percentage of total cost Findings

Substructures

Frame and upper floors

3%

10%

Foundations for the three-storey building are simple pads. Costs for the ground-floor slab and associated earthworks are identical for all solutions. On an overall basis, costs for the complete substructure were found to be lowest for the Composite and Slimdek options, with costs for the alternative options ranging from +2.4% to +7.3%. Costs for the earthworks and foundations only (excluding the GF slab) were found to be lowest for the Composite option, with costs for the alternative options ranging from +4.5% to +13.6%, which is the consequence of smaller pads being utilised for the lighter buildings.

When the costs of the frame and upper floors only are compared on a like-for-like basis, the most economic option is the Flat Slab, with costs for the alternative structural options ranging from +4.1% to +54.1%. A significant feature is the premium required to achieve a clear, flat soffit with the Slimdek system as opposed to with alternative flat soffit solutions, the Flat Slab and PT Flat Slab options. This is shown graphically and in tabular form below. It should be appreciated that, in cost plans, the infill to the steel core bracing in a steel-framed building is often allocated to the Internal Planning element. In this study, this would have produced an imbalance of approximately 7.5% in the comparisons, which has been adjusted in the table below. This highlights the need for designers to be aware that the structure of a cost plan may not readily reveal the full effects of the choice of a particular structural frame. Examination of the cost plan at a more detailed level than elemental totals may therefore prove beneficial in informing the structural choice.

Relative costs

£/m²

£/m² 180

*

160 140 120 100 80 60 40

Fire protection Decking & slabs Steel frame

GF slab Foundations Earthworks Percentage comparison with Flat Slab option

Note for frame and upper floors *Stairs have been excluded from the comparison, being of equal cost for all solutions.

Substructure costs

Slimdek

Steel + Hollowcore

PT Flat Slab


Composite


PT Flat Slab

Flat Slab

Steel + Hollowcore

Slimdek

0

Flat Slab

20

Composite

45 40 35 30 25 20 15 10 5 0

Formwork Reinforcement Concrete frame

Frame and upper floors costs £/m2

% difference

£/m2

Composite

£41

-

Flat Slab

£122

-

Slimdek

£41

-

Composite

£122

-

Steel + Hollowcore

£42

+2.4%


£127

+4.1%

Flat Slab

£43

+4.9%

PT Flat Slab

£138

+13.1%

PT Flat Slab

£43

+4.9%

Steel + Hollowcore

£139

+13.9%


£44

+7.3%

Slimdek

£188

+54.1%

% difference

52


02/10/2007 11:20:00


External cladding

Internal planning

17%

2%

For the costs of external cladding (curtain walling to main elevations and atrium, together with rain screens, brisesoleil, external doors and cladding to roof plant areas), the most economic option is the PT Flat Slab, with cost for the alternative solutions ranging from +0.9% for the Flat Slab option to +4.2% for the Steel + Hollowcore option. However, whilst the percentage variation between options may appear small, it should be borne in mind that, the actual cost variation can be significant for this element.

For the Internal planning (internal partitions, internal glazing to atrium, WC cubicles and internal doors) the most economic solutions are the Flat Slab and PT Flat Slab options in equal place. Costs for the alternative solutions range from +3.3% for the In-situ + Hollowcore option to +13.3% for the Steel + Hollowcore option.

The variation in cost is related to the area of cladding resulting from the necessary storey heights, which vary from 3950mm on the PT Flat Slab option to 4160mm on the Steel + Hollowcore option, to accommodate the different structural zones.

This cost range reflects the adjustment of the imbalance relating to the infill to steel braced cores, referred to in the Frame and upper floors element. Account has been taken in the costing of the added complexity of fire and acoustic sealing of partition heads against the irregular soffits of steel decking and around irregularly shaped intersecting steel frame members.

With the wall-to-floor ratio on this building form, a 5.3% increase in floor-to-floor height produces a 6.0% increase in cladding cost over three storeys.

£/m²

225

£/m²

**

35 30

220

25

215

20 15

210

10 205

Steel + Hollowcore

Composite

Slimdek


Flat Slab

PT Flat Slab

0

Steel + Hollowcore

Composite

Slimdek

Flat Slab

PT Flat Slab

200


5

Doors Atrium glazing Internal planning

External cladding costs £/m2

Internal planning costs £/m2

% difference

PT Flat Slab

£215

-

Flat Slab

£217

Slimdek Composite

% difference

PT Flat Slab

£30

-

+0.9%

Flat Slab

£30

-

£219

+1.9%


£31

+3.3%

£219

+1.9%

Slimdek

£33

+10.0%


£222

+3.3%

Composite

£33

+10.0%

Steel + Hollowcore

£224

+4.2%

Steel + Hollowcore

£34

+13.3%

Note for external cladding ** Undercroft treatment has been excluded from the comparison, being of equal cost for all solutions.

53


02/10/2007 11:20:02


Roof finishes and internal finishes, fixtures and fittings

Mechanical and electrical services

11%

34%

Percentage of total cost

The costs of the roof finishes were the same across all the structural options, as is also the case for the fixtures and fittings. Slight differences in internal finishes costs are entirely contained within the wall finishes and reflect the dissimilar storey heights, which differ by 5.3% between the lowest (the Flat Slab option) and the highest (the Steel + Hollowcore option). At this outline stage of design, these differentials are so small as to be lost in the rounding of the figures.

80 60 40

Ceiling finishes Wall finishes

Steel + Hollowcore

Flat Slab

Slimdek

Composite


0

PT Flat Slab

20

BWC Lifts Electical

Floor finishes

Finishes costs

Mechanical Sanitary

Mechanical and electrical costs £/m2

PT Flat Slab

Steel + Hollowcore

*

Composite

100

Slimdek

550 500 450 400 350 300 250 200 150 100 50 0

£/m²

Note for finishes *Roof finishes and fixtures and fittings have been excluded from the comparison, being of equal cost for all solutions.

However, with regard to the relative ease of installation of the mechanical and electrical services, a premium is incurred for the additional complexity where the services distribution has to be installed around downstand beams of varying depth, cross-section and number, as are found with the Composite and Steel + Hollowcore options.

£/m²

Relative costs

Percentage comparison with Flat Slab option

In respect of the direct costs of lifts, mechanical services, electrical services, sanitary installations and builder’s work in connection, there was no noticeable difference between all of the structural solutions.

PT Flat Slab

Findings


Elemental cost comparison.

Flat Slab

Table 1 cont’d Element

£97

% difference

£/m2

% difference

-

Flat Slab

£512

-


£97

-


£512

-

Composite

£97

-

PT Flat Slab

£512

-

Slimdek

£97

-

Slimdek

£512

-

Flat Slab

£97

-

Composite

£520

+1.6%

Steel + Hollowcore

£97

-

Steel + Hollowcore

£520

+1.6%

54


02/10/2007 11:20:04


Preliminaries

Contingency, overheads and profit

11%

12%

The budget for preliminaries for each option was based on two separate elements. A lump sum to allow for both nonwork-related aspects, such as contractual requirements for insurances, employer’s facilities, etc., together with fixed one-off costs such as site establishment, access roads, crane bases, services connection charges, etc.

A design contingency of 7.5% has been included within the budget costs, to reflect the outline nature of the design information developed at this stage of a project. The budget costs also contain an allowance of 6% in respect of overheads and profit. It should be borne in mind that, at this stage of the design, the allowance for contingency is the equivalent of 70% of the cost of the frame and upper floors on the most economic solutions.

The second element relates to time-related costs, such as management and staff, site accommodation, services and facilities, cranage, etc. Such costs therefore vary according to programme duration and the sequencing of operations within the programme. Adjustment of these costs has been made to reflect the different construction durations between 48 and 52 weeks identified in the programmes. (see Chapter 6 Programmes).

160 140

120

120

100

100

80

80

0

Slimdek


0

PT Flat Slab

20

Flat Slab

20

Steel + Hollowcore

60 40

Composite

60 40

Slimdek

160 140

Steel + Hollowcore

180

PT Flat Slab

180


£/m²

Composite

£/m²

Flat Slab

Detailed consideration of items within the Preliminaries, e.g. size of particular cranes, was beyond the scope of this study.

Overheads & profit Contingency

Time-related preliminaries Fixed preliminaries

Preliminaries costs

Contingency, overheads and profit costs £/m2

% difference

£/m2

% difference

Composite

£154

-

Flat Slab

£168

-

Steel + Hollowcore

£154

Slimdek

£154

-

Composite

£169

+0.6%

-


£170

+1.2%

Flat Slab

£158

+2.6%

PT Flat Slab

£170

+1.2%

PT Flat Slab

£160

+3.9%

Steel + Hollowcore

£173

+3.0%


£162

+5.2%

Slimdek

£177

+5.4%

55


02/10/2007 11:20:05

Study findings - Building B

Study findings – Building B

Overall costs Based on the building footprints and outline specifications compiled by Allies and Morrison, together with the structural design information and calculation provided by Arup, all eight structural options are within 5.5% of each other, after adjusting time-related preliminaries for construction programme differences. Of particular note is the significance of M&E services costs in the overall comparison, representing an average of 33% of total costs, and of the external cladding, representing an average of 21% of total costs. As illustrated in the figure and table, the Slimdek option was found to be 5.5% more expensive than the most economic option, the Flat Slab, with both options providing clear, unimpeded soffits. These figures are based on cost per m2 of gross internal area, with all options having concrete cores. In terms of overall construction costs, for short-span options, the most economic solution was found to be the Flat Slab option, with alternative solutions being between 0.7% and 5.5% more expensive. For long-span options, the PT Band Beam solution was found to be more economic than the Long-Span Composite solution. The Long span options are shown on the right of the charts as shown below. £/m² Short span

Long span

1750 1725 1700 1675 1650

Long span Composite

PT Band Beams

Slimdek

Steel + Hollowcore


Composite

1600

PT Flat Slab

1625

Flat Slab

Overall construction costs

£/m²

Overall costs £/m2

% difference

Flat Slab

£1,676

-

PT Flat Slab

£1,678

+0.1%

Composite

£1,691

+0.9%


£1,693

+1.0%

Steel + Hollowcore

£1,735

+3.5%

Slimdek

£1,759

+5.0%

PT Band Beams

£1,713

+2.2%

Long-Span Composite

£1,715

+2.3%

56


02/10/2007 11:20:06


Table 2 Element

Substructures


3%

8%

Foundations for Building B are piled, with varying pile depths, pile cap sizes and configurations for each option. Costs for the ground floor slab and associated earthworks are identical for all solutions. On an overall basis, costs for the complete substructure were found to be lowest for the Composite option, with costs for the alternative options ranging from +6.1% to +12.2%.

When the costs of the frame and upper floors only are compared, the most economic option is the Flat Slab, with costs for the alternative structural options ranging from +1.8% to +66.4%. A significant feature is the premium required to achieve a clear, flat soffit with the Slimdek system as opposed to with alternative flat soffit solutions, the Flat Slab and PT Flat Slab options. This is shown graphically and in tabular form below.

Costs for the earthworks and foundations only (excluding the GF slab) were found to be lowest for the Composite option, with costs for the alternative options ranging from +6.6% to +18.2%, which is the consequence of fewer piles, shorter pile lengths and smaller pile caps needed for the lighter buildings.

For the long-span options, the frame and upper floors costs were almost identical, the PT Band Beams option being 0.8% more expensive than the Long-Span Composite option. Both long-span solutions were an average of 22.3% higher than the most economic short-span solution, the Flat Slab.

£/m²

£/m² 200

Elemental cost comparison. Percentage of total cost

60 55 50 45 40 35 30 25 20 15 10 5 0

160 140 120 100 80 60 40

Note for frame and upper floors *Stairs have been excluded from the comparison for clarity, being of equal cost for all solutions.

Fire protection Decking & slabs Steel frame

Substructure costs

PT Band Beams

Long Span Composite

Slimdek

Steel + Hollowcore

PT Flat Slab

Composite


0

Flat Slab

PT Band Beams

Flat Slab

PT Flat Slab

Steel + Hollowcore

Slimdek

Composite

20

GF slab Foundations Earthworks Percentage comparison with Flat Slab option

*

180

Long Span Composite

Relative costs


Findings

Formwork Reinforcement Concrete frame

Frame and upper floor costs £/m2

% difference

Composite

£49

-

Slimdek

£52

+6.1%


£112

+1.8%

Steel + Hollowcore

£52

+6.1%

Composite

£114

+3.6%

PT Flat Slab

£53

+8.2%

PT Flat Slab

£122

+10.9%

Flat Slab

£54

+10.2%

Steel + Hollowcore

£138

+25.5%


£54

+10.2%

Slimdek

£183

+66.4%

Long-Span Composite

£52

+6.1%

Long-Span Composite

£134

+21.8%

PT Band Beams

£55

+12.2%

PT Band Beams

£135

+22.7%

Flat Slab

£/m2

% difference

£110

-

57


02/10/2007 11:20:07



External cladding

Internal planning

21%

1%

For the costs of external cladding (curtain walling to main elevations and atrium, together with rainscreens, brisesoleil, external doors and cladding to roof plant areas), the most economic option is the PT Flat Slab, with costs for the alternative solutions ranging from +1.7% for the Flat Slab option to +6.2% for the Steel + Hollowcore option. However, whilst the percentage variation between options may appear small, it should be borne in mind that, the variation in terms of actual cost can be significant for this element.

For the Internal planning (internal partitions, WC cubicles and internal doors) the most economic solutions are the Flat Slab, PT Flat Slab and In-situ + Hollowcore options in equal place. Costs for the alternative solutions are 22.2% higher, with minor differences between the Composite, Insitu + Hollowcore, Slimdek and Long-Span Composite options.

335

5

325

0

Long Span Composite

10

PT Band Beams

345

ISteel + Hollowcore

15

PT Band Beams

355

Long Span Composite

20

Steel + Hollowcore

365

Slimdek

25

In-Situ + Hollowcore

375

Composite

£/m²

Flat Slab

£/m²

PT Flat Slab

Relative costs

Such a large cost range reflects the effects of both the differences in storey height to accommodate the different structural zones and the cost premium incurred as a result of this added complexity.

Slimdek

With the wall-to-floor ratio on this building form, a 7.2% increase in floor-to-floor height produces a 6.1% increase in cladding cost over the six storeys.

Composite

The variation in cost is related to the area of cladding resulting from the necessary storey heights, which vary from 3950mm on the PT Flat Slab option to 4235mm on the Steel + Hollowcore option, to accommodate the different structural zones.

As with Building A, the costing takes account of the added complexity of fire and acoustic sealing of partition heads against the irregular soffits of steel decking and around irregularly shaped intersecting steel frame members. The effect of this factor on Building B is more significant due to the quantity of blockwork walls within the ground floor retail space.

In-Situ + Hollowcore

Findings

Flat Slab

Percentage of total cost

PT Flat Slab

Elemental cost comparison.

Doors Internal planning Percentage comparison with Flat Slab option

External cladding costs

Internal planning costs

£/m2

% difference

PT Flat Slab

£355

-

£/m2

% difference

PT Flat Slab

£18

-

Flat Slab

£361

Composite

£362

+1.7%

Flat Slab

£18

-

+2.0%


£18

Slimdek

-

£363

+2.3%

Composite

£22

+22.2%


£367

+3.4%

Slimdek

£22

+22.2% +22.2%

Steel + Hollowcore

£377

+6.2%

Steel + Hollowcore

£22

Long-Span Composite

£362

+2.0%

PT Band Beams

£18

-

PT Band Beams

£369

+3.9%

Long-Span Composite

£22

+22.2%

58


02/10/2007 11:20:09


Roof finishes and internal finishes, fixtures and fittings


10%

33%

The costs of the roof finishes were the same across all the structural options and they are therefore not included in the comparison of the internal finishes shown graphically and in tabular form below, which is also the case for the fixtures and fittings. For the internal finishes (floor wall and ceiling finishes) the most economic solutions are the PT Flat Slab and PT Band Beam option in equal place, with costs for the alternative solutions ranging from +0.8% for the Flat Slab, In-situ + Hollowcore and Long-Span Composite options, to +1.6% for the Composite, Steel + Hollowcore and Slimdek options.

In respect of the direct costs of lifts, mechanical services, electrical services, sanitary installations and builder’s work in connection, there was no noticeable difference between all of the structural solutions. However, with regard to the relative ease of installation of the mechanical and electrical services, a premium is incurred for the additional complexity where the services distribution has to be installed around downstand beams of varying depth, cross-section and number, as are found with the Composite, Steel + Hollowcore and Long-Span Composite options.

These differences in internal finishes costs are entirely contained within the wall finishes and reflect the dissimilar storey heights, which differ by 5.3% between the lowest (the Flat Slab option) and the highest (the Steel + Hollowcore option).

60 40

Ceiling finishes Wall finishes

Long Span Composite

PT Band Beams

Slimdek

Steel + Hollowcore

Composite

Flat Slab


0

PT Flat Slab

20

BWC Lifts Electical

Floor finishes

Finishes costs

Long Span Composite

80

PT Band Beams

100

Steel + Hollowcore

120

Composite

*

Slimdek

140

PT Flat Slab

£/m²

Flat Slab

600 550 500 450 400 350 300 250 200 150 100 50 0


£/m²

Mechanical Sanitary

Mechanical and electrical costs £/m2

% difference

£/m2

% difference -

PT Flat Slab

£127

-

Flat Slab

£562


£128

+0.8%


£562

-

Flat Slab

£128

+0.8%

PT Flat Slab

£562

-

Composite

£129

+1.6%

Slimdek

£562

-

Steel + Hollowcore

£129

+1.6%

Composite

£570

+1.4%

Slimdek

£129

+1.6%

Steel + Hollowcore

£570

+1.4%

PT Band Beams

£127

-

PT Band Beams

£562

-

Long-Span Composite

£128

+0.8%

Long-Span Composite

£570

+1.4%

Note for finishes *Roof finishes and fixtures and fittings have been excluded from the comparison for clarity, being of equal cost for all solutions.

59


02/10/2007 11:20:11



Preliminaries

Contingency, overheads and profit

12%

12%

The budget for preliminaries for each option was based on two separate elements. A lump sum to allow for both nonwork-related aspects, such as contractual requirements for insurances, employer’s facilities, etc., together with fixed one-off costs such as site establishment, access roads, crane bases, services connection charges, etc.

A design contingency of 7.5% has been included within the budget costs, to reflect the outline nature of the design information developed at this stage of a project. The budget costs also contain an allowance of 6% in respect of overheads and profit. It should be borne in mind that, at this stage of the design, the allowance for contingency is the equivalent of 87% of the superstructure cost on the most economic solution.

Elemental cost comparison. Percentage of total cost Findings

Separate allowances were made for time-related costs, such as management and staff, site accommodation, services and facilities, cranage, etc. Such costs therefore vary according to programme duration and the sequencing of operations within the programme. Adjustment of these costs has been made to reflect the different construction durations between 65 and 70 weeks identified in the programmes (see Chapter 6 Programmes). Detailed consideration of items within the Preliminaries, e.g. size of particular cranes, was beyond the scope of this study.

£/m² 200

£/m² 220 200

180

180

160

160

140

140

120

120

100

100

80

80

Long Span Composite

PT Band Beams

Slimdek

Steel + Hollowcore

Composite

Overheads & profit Contingency

Time-related preliminaries Fixed preliminaries Percentage comparison with Flat Slab option


Long Span Composite

PT Band Beams


Composite

0

Flat Slab

0

PT Flat Slab

20

Steel + Hollowcore

20

Slimdek

40

40

PT Flat Slab

60

60

Flat Slab

Relative costs

Preliminaries costs

Contingency, overheads and profit costs £/m2

% difference

£/m2

Slimdek

£199

-

% difference

Flat Slab

£191

Steel + Hollowcore

£199

-

-

PT Flat Slab

£191

PT Flat Slab

£201

-

+1.0%


£193

+1.0%

Flat Slab

£204

+2.5%

Composite

£193

+1.0%

Composite

£204

+2.5%

Steel + Hollowcore

£198

+3.7%


£211

+6.0%

Slimdek

£202

+5.8%

PT Band Beams

£201

+1.0%

PT Band Beams

£196

+2.6%

Long-Span Composite

£204

+2.5%

Long-Span Composite

£196

+2.6%

60


02/10/2007 11:20:12

Study findings

Summary comparison charts

It is evident from the study findings presented that the effects of the choice of a particular structural solution do not arise solely within the Frame and upper floors element of the cost plan. The charts below summarise those elements where costs are directly affected by the choice of frame and show the percentage variation in cost for each frame option, when compared with the most economic option, the Flat Slab, as the base case. The explanation of the reasons for the variations is given in the study findings above.

Building A

Flat Slab

Composite

In-situ + PT Flat Slab Steel + Hollowcore Hollowcore

Slimdek

–4.9%

+1.6%

+0.5%

–2.0%

–3.7%


+0.6%

+4.1%

+13.1%

+13.9%

+54.1%

External cladding

+0.8%

+2.1%

–1.1%

+3.3%

+0.9%

+10.0%

+3.3%

0%

+13.3%

+10.0%

–1.9%

–2.6%

–4.3%

+2.4%

–1.5%

+1.6%

0%

0%

+1.6%

0%

+1.0%

+1.0%

+1.2%

+3.1%

+6.1%

Time-related preliminaries

–3.9%

+3.9%

+2.0%

–3.9%

–3.9%


+0.6%

+1.2%

+1.2%

+3.0%

+5.4%

PT Flat Slab

Composite


PT Band Beams

Long-Span Composite

Steel + Hollowcore

Slimdek

Substructure

–2.9%

–8.5%

–0.7%

+1.8%

–4.8%

–3.4%

–4.4%


+10.9%

+3.6%

+1.8%

+22.7%

+21.8%

+25.5%

+66.4%

–1.7%

+0.1%

+1.7%

+2.3%

+0.1%

+4.3%

+0.4%

–1.1%

+19.7%

+1.1%

+1.4%

+19.7%

+23.4%

+20.0%

–1.9%

+9.5%

12.7%

–2.8%

+3.0%

+12.7%

+12.2%

0%

+1.4%

0%

0%

+1.4%

+1.4%

0%

+0.3%

+1.0%

+0.6%

+2.7%

+2.6%

+4.4%

+6.0%

Time-related preliminaries

–1.5%

0%

+4.6%

–1.5%

0%

–3.1%

–3.1%


+0.1%

+0.9%

+1.0%

+2.2%

+2.3%

+3.5%

+4.9%

Wall finishes M and E, lifts and BWIC Contingency

Building B

External cladding Internal planning Wall finishes M and E, lifts and BWIC Contingency

Flat Slab

Base case for comparison

Internal planning

Base case for comparison

Substructure

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02/10/2007 11:20:14


9. Commentary from The Concrete Centre Main conclusion

Differences in cost

The main conclusion to be drawn from the study is that, of the range of structural options commonly used in the construction of modern commercial offices, for both the threestorey out-of-town building and for the six-storey city centre building, the most economic structural solution was found to be the RC Flat Slab option. This produced savings of between 1% and 6% in overall construction costs in comparison with alternative solutions.

The main source of savings lies in the superstructure, when the frame, cladding and internal planning are all taken into account. There are minimal differences in the finishes, other than those caused by variations in storey heights depending on the structural solution adopted. Foundations for the heavier options cost more, but account for a relatively small proportion of the overall cost, the difference between the foundations for lighter and heavier buildings equating to less than 0.3% of the overall costs. Preliminaries are very similar, other than time-related aspects, although individual projects may have logistical difficulties, site constraints, access, adjacent buildings, etc. that are particular to that project and will affect the preliminaries. Such aspects are intrinsically project specific and are therefore beyond the scope of the study. There are no differences in the design or specification of the mechanical and electrical services as a result of the structural designs selected; however, those designs involving downstand beams of varying depths, cross-section and number incur a cost premium as a result of the added complexity of installing the services around such projections.

Foundations


A cost premium is incurred in the case of the buildings with the heavier structural frame. To some extent this cost premium can be offset by adopting post-tensioned slabs, which are typically some 15% lighter. In the case of Building B, the foundations to the posttensioned options are between 3% and 4% less expensive than those for the Flat Slab option.

With appropriate adjustment for the location of costs of core walls and bracing infill within the elemental summaries in order to achieve a like-for-like comparison, the frames and upper floors for the RC Flat Slab option have been shown to be less expensive than the alternative structural solutions, which were between 1% and 54% more expensive for Building A and between 2% and 66% more expensive for Building B.

62


02/10/2007 11:20:14


It should be appreciated that in most cost plans, the infill to the bracing of a steel-braced core, which is an integral component of the choice of structure, is generally not included within the costs of the structure, but is allocated to the Internal planning element. Consequently any comparison of the costs of the frame and upper floors only could be distorted by a significant amount.

External cladding

The thinner the overall structural and services zone, the lower the cladding cost. Given that the cladding on the buildings in the study represents between 17% and 22% of the construction cost, minimising the cladding area represents considerable value to the client. The minimum floor-to-floor height is almost always achieved with a flat soffit and separate services zone, offering the potential for additional storeys in high-rise buildings and thus improved rental or sales return. Smaller floor-to-floor heights have reduced cladding areas and hence lowered costs, and of increasing importance is the potential benefit that a reduced cladding area has on the building’s energy use.

Internal planning

It should be noted that a premium is incurred in sealing and fire stopping at partition heads against profiled soffits of metal decking and around non-rectangular-shaped intersecting frame members. Failure to consider this aspect can result in expensive and time-consuming remedial work later in the construction programme.


Mechanical and electrical services represent a large proportion of the overall construction costs of the buildings, averaging 34% for Building A and 33% for Building B. The design team was briefed not to design the services in detail, nor to take into account any benefits associated with the potential for fabric energy storage. Nonetheless, it should be noted that the removal of suspended ceilings in order to benefit from the thermal mass of the concrete within the buildings would reduce the overall capital project costs for all options by approximately 2% for Building A and by approximately 3% for Building B.

Types of ventilation Both buildings have been assumed as fully air-conditioned and, whilst natural ventilation and thermal mass can be used to eliminate air conditioning, these were not considered in this study.

Flexibility A flat soffit provides a clear zone for services distribution, free of any downstand beams. This reduces co-ordination effort for the design team and therefore the risk of errors, permits flexibility in design and allows co-ordination effort to be focused elsewhere. Services installation is simplest below a flat soffit, permitting maximum off-site fabrication of services, higher quality of work and quicker installation.

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02/10/2007 11:20:14


These advantages can typically produce cost savings on initial services installation costs but, more importantly, because they facilitate the use of pre-fabricated services equipment packages, they can offer reduced installation programmes, together with cost-in-use benefits in the form of reduced maintenance downtime due to ease of equipment changeout, greater flexibility and less disruption to an occupier’s business operations. Flat soffits also allow greater future adaptability for building refurbishment, new layouts and cellular arrangements; in addition, different service requirements are straightforward and more easily accommodated. These benefits are some of the main reasons for the development of Slimdek; however, this study shows the significant cost premium incurred with this option and shows how the RC Flat Slab or PT Flat Slab options are the most economic ways of getting a clear, flat soffit.

Nett lettable area

Differences in nett lettable area resulting from the different structural options adopted have not been considered in the study. However, it should be noted that there are two main areas in which such differences are found: stairs and core areas. Typically, stairs are re-sized as a result of the reduced storey height module, producing

slightly increased net lettable areas. The area occupied by a concrete core tends to be slightly smaller than that needed for a steel core, due to the allowance for steel bracing zones and the structural concrete walls serving a dual function as partitions. The RCC study - referred to in the Introduction - found that, on an overall basis, the difference can be as much as 1.5% extra nett lettable floor area, and this finding is still valid.

Programmes

General conclusions The lead times for the Flat Slab, In-situ + Hollowcore, PT Flat Slab and PT Band Beam options are significantly shorter than those for the Composite, Steel + Hollowcore, Slimdek and Long-Span Composite options. For Building A, during the eight-week saving in lead time, nearly 90% of the frame for the Flat Slab option could be constructed, whilst the 50 weeks overall construction programme for the Flat Slab option is only marginally longer than the 48 weeks for the Composite solution. For Building B, the ten-week saving in lead time equates to the period required to construct the frame for the Flat Slab up to fourth-floor level and commence the walls and columns from the fourth to fifth floor, i.e. approximately 60% of the complete frame. The overall construction programmes for the Flat Slab and the Composite options are identical at 67 weeks.

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02/10/2007 11:20:15


Construction programmes The programmes reflect a pragmatic contractor’s approach to the construction process. Inevitably, different planners would produce slightly different programmes based on a considerable number of variable factors. Overall project programmes are highly influenced by the procurement route and type of contract adopted, and alternative procurement approaches such as construction management or design and build would no doubt produce different results. For example, construction management and design and build approaches lend themselves to concrete construction, where the ability to accommodate late information and variations are particularly beneficial, as the work can be let before the design of following packages has been finalised. The programmes prepared for this study reflect one procurement approach but, in practice, contractors are more likely to programme to a pre-set completion date in the knowledge of the type of contract, their projected costs, the risk profile of the project, their knowledge of and relationship with the client and design team, their supply chain and their exposure to both liquidated damages and to market forces in play at the time of the project. A practical view had to be taken of such factors as logistics, site access, boundary constraints, cranage, etc., which are essentially site-specific. It could be argued that the steelwork could have started on-site sooner, with earlier sub-contract award or longer periods for design, package tendering, mobilisation or foundations making the steelwork lead time less critical or even non-critical. Conversely, the use of a purely domestic sub-contract, without the ability to pre-order, would push the programme back. Whereas fire protection used to be a critical activity, modern details such as site-applied intumescent coating have removed fireproofing from the critical path altogether. However, although not on the critical path, the fireproofing activity requires a greater level of detailing and causes disruption that can adversely affect other trades, e.g. difficulties caused by fixings penetrating through fire-proofing and damage needing rectification. Off-site intumescent coatings have been introduced in an effort to reduce the construction time, but these can suffer from significant damage in transit, requiring site remedial work which can eliminate the original saving. The durations of first fix, second fix and M&E installations are essentially the same, with slight differences in quantities appearing to make little difference to the programmes. However, it is becoming increasingly common to use prefabrication for the M&E services distribution, which can offer programme advantages when used in conjunction with the open flat soffits provided by the Flat Slab, PT Flat Slab and Slimdek options. Prefabrication of sections of the M&E installations also offers advantages in subsequent maintenance and refurbishment of the building. No account is taken within the programmes of any construction time savings resulting from such prefabrication.

65


02/10/2007 11:20:15


Finance costs

Although the reported costings excluded the effects of finance costs, if finance costs were to be considered, they should not be limited to the construction period alone as, in most cases, finance costs also affect the procurement and lead times. It is not possible to examine the entire project from inception to completion, as the duration prior to the commencement of procurement cannot be defined on a generic basis. However, consideration of the periods that have been identified in the programmes for procurement, lead time and construction would produce the following comparison, assuming a rate of 7.75% p.a. (base rate + 2%) and comparing the programme extension or saving against the most economic short-span solution, the Flat Slab option. The PT Band Beam option has been compared with the Long-Span Composite option.

Building A Construction cost in £/m2

Flat Slab

Composite


PT Flat Slab

Steel + Hollowcore

Slimdek

£1,460

£1,468

£1,477

£1,477

£1,495

£1,534

64

70

66

65

70

70

Overall programme in weeks Savings in finance costs @ 7.75% p.a.

Building B Construction cost in £/m2

+£0

+£5

+£2

+£1

+£5

+£5

£1,460

£1,473

£1,479

£1,478

£1,500

£1,539

Flat Slab PT Flat Composite In-situ + PT Band Long-Span Steel + Slimdek Slab Hollowcore Beams Composite Hollowcore £1,676

£1,678

£1,691

£1,693

£1,713

£1,715

£1,735

£1,759

Overall programme in weeks

83

82

93

86

83

95

91

91

Savings in finance costs @ 7.75% p.a.

+£0

-£1

+£7

+£2

+£0

+£8

+£6

+£6

£1,676

£1,677

£1,698

£1,695

£1,713

£1,723

£1,741

£1,765

This comparison takes no account of differences in cumulative finance costs arising from the different cash flow profiles experienced with the differing forms of construction. For example, the Composite, Steel + Hollowcore, Slimdek and Long-Span Composite options require greater expenditure early on than the Flat Slab, In-situ + Hollowcore, PT Flat Slab and PT Band Beam options, where the ‘pay as you pour’ principle works in the client’s favour. A more comprehensive analysis of the construction cash flow profiles would be required in order to present a detailed comparison of these effects on finance costs.

Other value considerations

Initial capital cost is not, of course, the sole driver for clients, whose main objective is optimum value from an overall solution. The wider value aspects of structural solutions in relation to framed buildings are therefore briefly considered in more detail below.

Overall value vs frame cost Frame cost alone should not dictate the choice of structural solution. Rather it should be just one of a number of value issues that should be borne in mind when making the choice of frame material. Only then can one be confident that the optimum structural solution has been selected.

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02/10/2007 11:20:16


Fire protection For Flat Slab, In-situ + Hollowcore, PT Flat Slab and PT Band Beam structures, fire protection is generally not needed, as the material has inherent fire resistance of up to four hours. This removes the time, cost and separate trades required for fire protection. Added value benefits include such factors as enhanced property safety, the potential for lower insurance premiums, re-usability of the structure and considerably reduced down-time for an occupier after a fire.

Exposed soffit Potential value to a client exists in those structures with a high thermal mass. By exposing the soffits, this can be utilised through fabric energy storage (FES) to reduce initial plant costs, by minimising or eliminating the need for air conditioning and substantially reducing the lifetime operational costs of the asset. Utilisation of FES permits the designer to create naturally ventilated buildings, giving occupants the chance to control their environment, with consequent improvements in employee productivity. Furthermore, suspended ceilings can be reduced or eliminated, giving valuable initial cost and programme benefits and reduced lifetime maintenance costs.

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Appendix A - Detailed programmes

10. Appendix A – Detailed programmes

Line

Name

1

Site Set Up

2

Substructure Remove Topsoil & RL Dig Pad Foundations Underslab Drainage Ground Floor Slab

3 4 5 6

7 8 9 10 11 12 13 14

1

2

3

4

5

6

7

8

9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51

1 2 3 4 5 6

Superstructure Walls / Columns Grd to 1st 1st Floor Slab Walls / Columns 1st to 2nd 2nd Floor Slab Walls / Cols 2nd to 3rd 3rd Floor Slab Roof Upstands & Bases

7 8 9 10 11 12 13 14

Roof Installations Roof Finishes Deliver Main Roof Plant Roof MEP Installations Install Plant Screen Louvres

15

20

24

Curtain Wallling/External Cladding Survey/Set Out Brackets Secondry Steelwork/Framing Glazing & Spandrel Panels Capping/Flashing & Roof Upstand Level

25

Building Watertight

26

Cores & Risers MEP Risers Toilet Fit Out Lift Installations

15 16 17 18 19

20 21 22 23

27 28 29

16 +

+ 17 18 19

21 22 23 24

25

26 27 +

+ 28 +

+

29 +

+

30

31

Office Fit Out to Cat A Level 2

32

H/L MEP 1st Installations

32

33

Suspended Ceiling Grid & Service Tiles

34

H/L MEP 2nd Fix

35

Raised Flooring

30

36 37 38

33 34 35

Joinery 1st Fix

36

Level 1 Level G

37 +

+ 38 +

39

Close Out

40

Testing & Commissioning

41

External Works

42

Completion

Line

31

+

39 +

+

40 +

+

41

42

Name

Client Project

Title

Programme

Title

1

2

3

4

5

6

7

8

9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 Dated

11/07/2006

The Concrete Centre

Revision comment

COMMERCIAL BUILDINGS - COST MODEL STUDY

Notes

Drawn by

Programme No

rev

Building A : Scheme 1 - Flat Slab

68


02/10/2007 11:20:17


Line

Name

1

Site Set Up

2

Substructure Remove Topsoil & RL Dig Pad Foundations Underslab Drainage Ground Floor Slab

3 4 5 6

7 8 9 10 11

12 13 14 15 16

17 18 19 20 21

22

23 24 25 26

27 28

1

8 9 10 11

Roof Installations Roof Finishes Deliver Main Roof Plant Roof MEP Installations Install Plant Screen Louvres

12

Curtain Wallling/External Cladding Survey/Set Out Brackets Secondry Steelwork/Framing Glazing & Spandrel Panels Capping/Flashing & Roof Upstand Level

17

28 29

32 33

Name

9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 Dated

Drawn by

11/07/2006

2 3 4 5 6 7 8

Superstructure Walls / Columns Grd to 1st 1st Floor Slab Walls / Columns 1st to 2nd 2nd Floor Slab Walls / Cols 2nd to 3rd 3rd Floor Slab Walls / Columns 3rd to 4th 4th Floor Slab Walls / Cols 4th to 5th 5th Floor Slab Cols / Walls 5th to 6th Roof Slab Roof Upstands & Plant Bases

Building Watertight Cores & Risers M&E Risers Toilet Fit Out Lift Installations

9 10 11 12 13 14 15 16

2d

17 18 19 20

21 22

23 24 +

+ 25 +

+ +

28

29 30 +

+ 31 +

34 35


35

36

Perimeter Ceiling Plasterboard Margin

37


38

H/L MEP 2nd Fix

39

Raised Flooring

40

Joinery 1st Fix

42 43 44 45 46 47 48

Line

+ 32 +

33

Level Level Level Level

+

26 + 27 +


41

rev

1

29

33

Programme No

1 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68

28

32

8

Building A : Scheme 4 - Composite

27

31

7

Notes

Envelope Roof Finishes Roof Installations Atrium Glazing Curtain Wallling/External Cladding

30

6

Revision comment

Substructure Pile Probing Form Pile Matt Piled Foundations Excavate & Form Pile Caps Underslab Drainage Ground Floor Slab

26

5


2

25

4

The Concrete Centre

Site Set Up

24

3

Client

1

23

2

Project

Title

22

+

39

1

Title

21

+

37 +

38

Programme

20

+

36 +

Name

Line

+ 35 +

Completion

19

30

Level 1 Level G

39

18

+ +

27

31

Line

17

+

34 +

External Works

16

21


38

15

20

26 +


14

19

25 +

37

13

18

24 +

Close Out

12

16

23

36

11

15

Cores & Risers MEP Risers Toilet Fit Out Lift Installations

Joinery 1st Fix

10

+ 14

22

33

9

13 +

Building Watertight

Raised Flooring

8

9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49

7

H/L MEP 2nd Fix

7

8

6

32

6

7

Superstructure Steelwork Metal Decking RC Topping Roof Upstands & Bases

31

5

6

5


4

5

4


3

4

3

30

35

3 2

29

34

2

1

+

34

36 37 38 39 40

2 3 4 5

41 +

+ 42 +

+ 43 +

+ 44 +

Close Out Testing & Commissioning External Works Completion Name

Client Project

Title

Programme

Title

+

45 +

+

46 +

+ 47 48

1 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 Dated

28/06/2006

The Concrete Centre

Revision comment


Notes

Drawn by

Programme No

rev

Building B : Scheme 1 - Flat Slab

69


02/10/2007 11:20:54


Line

Name

1

Site Set Up

2

Substructure Pile Probing Form Pile Matt Piled Foundations (128 No) Excavate & Form Pile Caps Underslab Drainage Ground Floor Slab

3 4 5 6 7 8 9 10 11 12 13 14

1 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 1

2 3 4 5 6 7 8

Superstructure Concrete Core (jump form) Structural Steelwork Metal Decking RC Topping Upstands/Bases at Roof Level

19

Envelope Roof Finishes Roof Installations Atrium Glazing Curtain Wallling/External Cladding

20

Building Watertight

21

Cores & Risers M&E Risers Toilet Fit Out Lift Installations

15 16 17 18

22 23 24

9 10 11 12

45d

13

14

15 16 +

+ 17 +

+ +

20

21 22 +

+ 23 +


25

27


27

28

Perimeter Ceiling Plasterboard Margin

29


30

H/L MEP 2nd Fix

31

Raised Flooring

32

Joinery 1st Fix

33 34 35 36

Level Level Level Level

+

26

28 29 30 31 32

2 3 4 5

33 +

+ 34 +

+ 35 +

+ 36 +

37

Close Out

38


39

External Works

40

Completion

Line

+ 24 +

26

25

+

18 + 19 +

+

37 +

+

38 +

+

39

40

Name

Client Project

Title

Programme

Title

1 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 Dated

28/06/2006

The Concrete Centre

Revision comment


Notes

Drawn by

Programme No

rev

Building B : Scheme 4 - Composite

70


02/10/2007 11:20:59


02/10/2007 11:21:03

CCIP-010

CI/Sfb

UDC


624.94.04.033



A comparative cost assessment of the construction of multi-storey office buildings A report commissioned by The Concrete Centre

Francis Ryder, Head of Cost at The Concrete Centre, has project managed this cost model study for commercial buildings. For more information visit www.concretecentre.com/publications A report commissioned by The Concrete Centre

This comprehensive and independent cost study was undertaken to evaluate a number of structural frame options for a three-storey office building in an out-of-town location and a six-storey office building in a city centre location. A total of 14 floor design options were evaluated, budget costings were assigned to all elements of construction and adjustments were made to reflect time-related costs attributable to differences in the construction programme.


The publication outlines the analysis, the detailed costings and programmes for each structural alternative, and provides a useful resource for architects, engineers and contractors involved with evaluating the cost competitiveness of structural options for multi-storey office construction.

CCIP-010 Published October 2007 ISBN 1-904482-36-8 Price Group P © The Concrete Centre

Riverside House, 4 Meadows Business Park, Station Approach, Blackwater, Camberley, Surrey, GU17 9AB Tel: +44 (0)1276 606 800 www.concretecentre.com


01/10/2007 11:26:58

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