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IP-010C

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Cost Model Study –Commercial BuildingsA comparative cost assessment of the construction of multi-storey offi ce buildings

A cement and concrete industry publication

A report commissioned by The Concrete Centre

Cost Model Study – Commercial Buildings

This comprehensive and independent cost study was undertaken to evaluate a number of structural frame options for a three-storey offi ce building in an out-of-town location and a six-storey offi ce building in a city centre location. A total of 14 fl oor design options were evaluated, budget costings were assigned to all elements of construction and adjustments were made to refl ect 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 offi ce construction.

CCIP-010 Published October 2007 ISBN 1-904482-36-8Price Group P

© The Concrete Centre

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

CI/Sfb

UDC624.94.04.033

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

CMS-commercial cover.indd 1CMS-commercial cover.indd 1 01/10/2007 11:26:5801/10/2007 11:26:58


Published by The Concrete CentreRiverside 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 atwww.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 signifi cance 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.

AcknowledgementsThe 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 DesignEstablished 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 fi rm of consulting engineers, with over 55 years of international experience in providing consultancy in engineering, design, planning and project management services in every fi eld related to building, civil, and industrial projects. Arup aims to provide a consistently excellent multi-disciplinary service by adding value through technical excellence, effi cient organisation, personal service and a strong commitment to sustainable design. www.arup.com

Davis Langdon LLP - Quantity SurveyingDavis 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 specifi c 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 fi nding 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.



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 fi ndings 49

9. Commentary from The Concrete Centre 62

A1. Appendix A – Detailed programmes 68

Commercial Buildings - Cost Mode1 1Commercial Buildings - Cost Mode1 1 02/10/2007 11:18:4902/10/2007 11:18:49

3

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 fi t-out, and the effect of programme times on cost.

Designs were commissioned for a three-storey offi ce building in an out-of-town business park location in the south east and a six-storey offi ce building located in central London. The buildings were based upon appropriate structural grids commonly in current use, with designs and specifi cations 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 pre-liminaries, with the exception of external works, which were considered to be too highly site-specifi c to permit accurate costing. Adjustments were made to the costings to refl ect 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 benefi ts 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 fi fth 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 Post-Tensioned 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 fi fth place (+3.5%), with the Slimdek option again being the least economic (+5.0%). Of the two long-span options on this building, the Post-Tensioned Band Beam option and the Long-Span Composite option are respectively 2.2% and 2.3% more costly than the Flat Slab option.


4

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 fl ow, overall project time, fi re protection, use of fl at soffi ts and lower fl oor to fl oor height are discussed in detail in the study.

Summary


5

Introduction

2. Introduction

This Cost Model Study – Commercial Buildings was undertaken to provide both a com-parison 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 identifi ed that this study needed to be updated because building types in the contemporary market are signifi cantly 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, fi re protection, services, fi t-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 specifi cations 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 refl ecting 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.


6

Method of study

3. Method of study

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 refl ect 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 offi ce building in an out-of-town business park location in the south east (Building A) and a six-storey offi ce building located in central London (Building B). The buildings were based upon appropriate structural grids commonly in current use, using pad or piled foundations. Specifi cations 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 rec-tangular, air-conditioned building with curtain walling.

Building A was chosen to refl ect a framed building of average size (4,650m2) in a com-mercial/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 fl oor level, was chosen to refl ect a high-quality framed building of average size (14,200m2 of offi ces 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.

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.

Brief

Concepts and initial studies


7

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 fl oor plates 23.5m wide, confi gured 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 fl oor to ceiling double glazing units and aluminium clad insulated spandrels, permitting good daylighting to most of the working areas.

Method of study

Building A: Three-storey. Building B: Six-storey.

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


8

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 fl oor to ceiling double-glazing units and stone clad insulated spandrels.

The fl oor 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 compari-son, as this may also have unduly favoured some structural solutions over others. This is a potential benefi t 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 fl oor areas were to be approximately 1,500m2 per fl oor based on a 7.5 × 7.5m structural grid for Building A and approximately 2,750m2 per fl oor 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 fi gures which follow.


9

Method of study

The two buildings were taken up to normal outline design stage. The buildings were all to commercial developers’ standards with associated outline specifi cations. The only diffe-rences were directly attributable to the choice of structural solution.

The architectural schemes, layouts and specifi cations 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.

Offi ce fl oors were designed to be for an open-plan confi guration on a 1.5m planning module, to allow for possible subdivision of the fl oors into two tenancies. Cellular offi ce layouts were allowed for. Potential partitions may be aligned with external wall mullions or piers at 1.5m centres. Initial fl oor plans and core layouts were adjusted and modifi ed following liaison and discussion between the design team members. In particular, core areas were modifi ed 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-specifi c as to preclude meaningful consideration. The extent, layout and complexity of external works are to a large extent dictated by the size, confi guration 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 infl uenced to any signifi cant 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.

Short-span options - Building A and B Long-span options - Building B only

Option 1 - Flat Slab Option 2 - Composite Option 3 - PT Flat Slab Option 7 - PT Band Beams

Reinforced In-situ concrete fl at slab and columns

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

Post-tensioned In-situ concrete fl at slab and reinforced In-situ concrete columns

Post-tensioned In-situ concrete fl at 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 fl oor slabs. Steel columns

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

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

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

Scheme designs


10

Specifi cations and drawings

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

Design criteria and outline specifi cations were fi nalised 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 specifi cations Architectural, structural and services

Architectural drawings Typical fl oor plans

Structural drawings Partial fl oor plans and fl oor 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

Costings were based on drawings and specifi cations 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 pre-pared 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 specifi cations 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.

Detailed construction programmes were prepared on the basis of the drawings, specifi ca-tions 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.

Basis of costing and quantities

Planning and programming

Method of study


11

Building A - Design criteria

4. Building A

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

Plan dimensionsPlanning grid 1500 × 1500mm

Partition grid 1500 × 1500mm

Structural grid 7500 × 7500mm

Vertical dimensions 3950–4160mm (see drawings)

Floor to ceiling height 2700mm

Raised fl oor 250mm

Occupancy

Density One person per 10m2 of nett internal fl oor area.

Design target populations Three-storey 407 total, 319 on upper fl oors.

Ancillary accommodation

Core areas Include male and female toilets and cleaners’ cubicle on each fl oor, disabled toilets and PABX equipment on the ground fl oor.

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 Offi ces: 4.0 + 1.0kN/m2 for partitionsRoof: 0.75kN/m2

Dead load Self-weight plus superimposed dead load of 0.9kN/m2

Line loads External cladding 8kN/mAtrium glazing 8kN/mInternal blockwork walls 10kN/m

Defl ections

General Defl ections 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

Bearing pressure It has been assumed that the site provides a bearing capacity suitable for pad foundations and a ground-bearing ground fl oor 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, fi re services, small power, provision for communications, lightning protection, etc.

Ventilation

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

Design criteria

Architectural

Structural

Services


12

Building A - Outline specifi cations

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 fl oor 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.

Offi ce areas

Floors Proprietary medium duty raised fl oor system, 250mm overall, and carpet.

Ceilings 500 × 500mm pre-fi nished fully demountable perforated tile with concealed suspension system.

External walls Grid stick curtain wall incorporating fl oor 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 fl ush painted softwood.

Entrance halls/ground fl oor lift lobbies

Floor Carpet.

Walls Emulsion painted dry-lining or plaster.

Ceilings Pre-fi nished 500 × 500mm metal tile with concealed grid.


Furniture Reception desk.

Doors Stainless steel revolving doors.

Lift lobbies (upper fl oors)

Floors Carpet.



Toilets

Floor Unglazed ceramic tiles.

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


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 fi ttings and shaving point.

Hand drying Recessed paper towel dispensers.

Outline specifi cations

Architectural


13


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 Emulsion painted suspended plasterboard dry-lining.

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

Enclosed Floors: screed laid to falls. Walls/ceilings: unfi nished structure/blockwork.

Open/external Precast paving slabs and gravel ballast.

Intake room Unfi nished 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

Structural frames Specifi cation as given on partial fl oor plans.Plant room enclosures: steel frame (25kg/m2) supporting lightweight cladding.

Fire One hour fi re protection to all structural members apart from roof structure (no fi re 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 offi ce areas.

Internal thermal loads:Occupants 8W/m2

Offi ce lighting 10W/m2

Offi ce small power 18W/m2

Occupancy One person per 10m2.

Fresh air allowance 12 litres per second per person.

Supply All offi ces 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 fi red boiler plant in roof plant room.

Architectural continued..

Structural

Services


14


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 Offi ces:Lighting 12W/m2

Small power 15W/m2

Air conditioning 60W/m2

Miscellaneous 10W/m2

Lighting Generally to L2 offi ce standard; control by switches with key switches for the emergency fi ttings. Emergency fi ttings to be self-contained.

Small power Distribution within raised fl ooring via fl oor boxes. Cleaners’ sockets to walls and circulation spaces.

Communications Provision within fl oor 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 fi ve minute period.

Services


15

Building A - Architectural drawings

Architectural drawings

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

Typical fl oor plan

A B C D

7500 7500 7500

7500 7500 7500 7500 7500

E F G H I

6

5

4

3

2

1

7500

7500

7500

7500

7500

Full height atrium


16

Building A - Structural drawings

Structural drawings

All Columns450 x 450 unlessotherwise noted

Full HeightAtrium

Lifts Void

Void

Stairs

ToiletZone

7500 7500 7500 7500

7500

7500

7500

7500

200mm R C Shear walls

800 ØR C Column

800 ØR C Column

300

600

150

300 mm RC slab

Services zone

Ceiling and lighting zone

Section through floor zone

1050

Flat Slab1. 300mm concrete flat slab 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: 300mm Services zone: 600mm Floor zone = 1050mm Ceiling/lighting: 150mm Floor to ceiling: 2700mm Raised floor: 250mm Total: 4000mm

]


17

Composite1. 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


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 (1) including downstand beams

350 (min)

130

457 x 152 UB52

Services zone



150

A193 mesh

1.2mm ribdeck AL1087

800 (min)

Lift

7500

406 x 140 UB46 406 x 140 UB46 406 x 140 UB46 406 x 140 UB46

356

x12

7U

B33

356

x12

7U

B33

356

x12

7U

B33

356

x12

7U

B33

356

x12

7U

B33

356

x12

7U

B33

356

x1 2

7U

B33

356

x1 2

7U

B33

356

x12

7U

B33

7500 7500 7500

7500

6000

7500

7500

7500

Void 406 x 140 UB46

457 x 152 UB52457 x 152

UB52

254

x10

2U

B25

356

x1 2

7U

B33

356

x12

7U

B33

356

x12

7U

B33

356

x12

7U

B33

356

x1 2

7U

B33

ToiletZone

457 x 152 UB52

457 x 152 UB52

457 x 191UB82

457 x 152 UB52

457 x 191 UB67

356

x12

7U

B33

406

x14

0U

B39

406

x1 4

0U

B39

356

x12

7U

B33

Full HeightAtrium

356

x12

7U

B33

508ØCHS153457 x 152 UB52

356

x12

7U

B33

356

x12

7U

B33

406 x 140 UB46

356

x12

7U

B33

356

x1 2

7U

B33

356

x12

7U

B33

Void

203 x 203 UC46

508ØCHS153

Stairs

457

x19

1U

B82

457

x19

1U

B82

203 x 203 UC46 C3C3

C3 C3

C1 C1

C2C2

C2 C2 C3 C3 C1

C3 C1 C1

C1C2C2C2C2

203 x 203UC46

C3 = 305 x 305 UC97

C2 = 254 x 254 UC89

C1 = 254 x 254 UC73

406 x 140UB39 40

6x

140

UB3

9

]



18


Void

Void

Full HeightAtrium

7500

7500

7500

7500

7500750075007500

600 x 600 R C Beam (typical)All Columns400 x 400 unlessotherwise noted

ToiletZone

Lifts

600 x 250 R C Beam (edge)

200mm R CShear walls

Stairs

800 ØR C Column

800 ØR C Column

600 x 250 R C Beam (trimmer)

200

800(min)

600

Services zone



A142 mesh in 50mm (min) structural topping

250

150mmhollowcore

450 450

425

600

1150

600

350(min)

150

50

Typical edgebeam

600

In-situ + Hollowcore1. 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


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) including downstand beams

]


19


Full HeightAtrium

Lifts Void

Stairs

ToiletZone

7500 7500 7500 7500

7500

7500

7500

7500

200mmR C Shear walls

800 ØR C Column

800 ØR C Column


Void

250

600

1000

150

Services zone



Reinforcement

250mm Post-tensioned slab

PT duct

PT Flat Slab1. 250mm post-tensioned concrete flat slab 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


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

]


20

7500 7500

139.7 x 5.0 CHSФ 139.7 x 5.0 CHSФ 139.7 x 5.0 CHSФ 139.7 x 5.0 CHSФ

139.7 x 5.0 CHSФ139.7 x 5.0 CHSФ

139.7 x 5.0 CHSФ

139.7 x 5.0 CHSФ

457 x 191 UB74

457

x19

1U

B67

457

x19

1U

B67

457

x19

1U

B67

7500 7500

7500

6000

7500

7500

7500

Void533 x 210 UB82 406 x 140 UB39

457 x 191 UB67

406 x 140 UB39406 x 140 UB39

406

x17

8U

B54

406

x1 7

8U

B54

457

x19

1U

B67

457

x19

1U

B67

457

x19

1U

B67

Lifts

ToiletZone45

7x

191

UB6

7

533 x 210 UB82

457

x19

1U

B67

406

x17

8U

B54

152 x89 UB16

508Ø CHS153

406

x17

8U

B54

406

x17

8U

B54

457

x19

1U

B67

Void

203 x 203 UC60

406 x 178 UB54

305

x30

5U

C97

203 x 203UC60

406

x17

8U

B54

508Ø CHS153

457

x19

1U

B67

Full HeightAtrium

Stairs

305

x30

5U

C97203 x 203 UC60

C2C2C2

C2

C2

C2

C2C2

C2

C2

C2

C1C3C3

C4 C4C4

C3

C1

C3 C3

C3 = 305 x 305 UC118

C4 = 305 x 305 UC137

C2 = 305 x 305 UC97

C1 = 254 x 254 UC89


350 (min)

250

457 x 191 UB67

Services zone



150

A142 mesh in 50mm structural topping

200 mm Hollowcore

1207

800 (min)

Steel + Hollowcore1. 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


Offices: 5.0kN/m2

5. Vertical dimensions: Slab: 250mm Services zone(1): 807mm Floor zone = 1207mm Ceiling/lighting: 150mm ≈ 1210mm Floor to ceiling: 2700mm Raised floor: 250mm Total: 4160mm (1) including downstand beams

]


21


Void

300

ASB

155

300

ASB

155

203 x 102 UB23

203 x 102 UB23 203 x 102 UB23 203 x 102 UB23 203 x 102 UB23

75007500 7500 7500

Lifts Void

Stairs

305

x305

UC97

203 x 203 UC60

203 x 203 UC60

200 ASB124

203 x 203UC60

305

x305

UC97

508Ø CHS153

508Ø CHS153

280ASB74

300

ASB

155

300

ASB

155

300

ASB

155

300

ASB

155

300

ASB

155

300

ASB

155

300

ASB

155

300

ASB

155

300

ASB

155

300

ASB

155

300

ASB

155

300

ASB

155

300

ASB

155

300

ASB

155

203 x 102 UB23

203 x 102 UB23

300 ASB196

300 ASB196

203 x 102 UB23

300 ASB196 300 ASB196 280 ASB74

7500

7500

7500

7500

6000

Full HeightAtrium

ToiletZone

C1 = 254 x 254 UC89

C2 = 254 x 254 UC107

C3 = 305 x 305 UC97

C4 = 305 x 305 UC118

C5 = 305 x 305 UC137

C3C3

C3C3

C3C1

C2 C4 C5 C1

C1C2

C2

C5

C2 C2

C5 C5

C2 C1

C1

342

600

150

SD225 Deep decking

Services zone



1092

In situ concrete slab

300 ASB 155

A193 mesh

Slimdek1. 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


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

]


22

Building B - Design criteria

5. Building B

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

Plan dimensionsPlanning 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 fl oor 250mm

Occupancy

Density One person per 10m2 of nett internal fl oor area.

Design target populations 1,215 total.Ancillary accommodation

Core areas Include male and female toilets and cleaners’ cubicle on each fl oor, disabled toilets and PABX equipment on the ground fl oor.

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 Offi ces: 4.0 + 1.0kN/m2 for partitionsRoof: 0.75kN/m2

Dead load Self-weight plus superimposed dead load of 0.9kN/m2

Line loads External cladding 8kN/mAtrium glazing 8kN/mInternal blockwork walls 10kN/m

Defl ections

General Defl ections 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.

It is assumed that the ground does not have suffi cient capacity to carry a ground-bearing slab and that all options would have a rein-forced In-situ concrete suspended slab. In long-span options, inter-mediate piles are provided to reduce the span of this ground slab.

Lateral stability Braced frame using shear walls.

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

Design criteria

Architectural

Structural


23

Services

Building B - Outline specifi cations

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

Ventilation

General Air-conditioned using four-pipe fan coil system.

External envelope

External wall Proprietary curtain walling system, 170mm thick overall.

Shop fronts atground fl oor

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 fl oor-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.

Offi ce areas

Floors Proprietary medium duty raised fl oor system, 250mm overall, and carpet.

Ceilings 500 × 500mm pre-fi nished fully demountable perforated tile with concealed suspension system.

External walls Unitised curtain wall incorporating fl oor 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.


Retail space

Generally left as shell fi nish for fi t-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 ground-bearing blockwork walls or grid frame.

Entrance halls/ground fl oor lift lobbies

Floor Carpet.




Furniture Reception desk.

Doors Stainless steel revolving doors.

Lift lobbies (upper fl oors)

Floors Carpet.



Outline specifi cations

Architectural


24


Toilets

Floor Unglazed ceramic tiles.

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


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 fi ttings, 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 Emulsion painted suspended plasterboard dry-lining.

Ceilings Emulsion painted suspended plasterboard dry-lining.

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

Enclosed Floors: screed laid to falls. Walls/ceilings: unfi nished structure/blockwork.

Open/external Precast paving slabs and gravel ballast.

Intake room Unfi nished 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 Specifi cation as given on partial fl oor plans.Plant room enclosures: steel frame (25kg/m2) supporting lightweight cladding.

Steel Steel frames as shown on partial fl oor plans.

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

Architectural continued..

Structural


25


Air conditioning

Design data 22°C dry bulb +/– 1°C.50% RH +10%/–15% RH.0.25 air changes per hour for offi ce areas.

Internal thermal loads:Occupants 8W/m2

Offi ce lighting 10W/m2

Offi ce small power 18W/m2

Occupancy One person per 10m2.

Fresh air allowance 12 litres per second per person.

Supply All offi ces 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 fi red 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 Offi ces:Lighting 12W/m2

Small power 15W/m2

Air conditioning 60W/m2

Miscellaneous 10W/m2

Lighting Generally to L2 offi ce standard; control by switches with key switches for the emergency fi ttings. Emergency fi ttings to be self-contained.

Small power Distribution within raised fl ooring via fl oor boxes. Cleaners’ sockets to walls and circulation spaces.

Communications Provision within fl oor 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 fi ve minute period.

Services


26

Building B - Architectural drawings

Architectural drawings

Typical fl oor plan

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

9000 9000 9000 9000 9000 9000 9000 9000

7500

7500

9000

7500

7500

A B C D E F G H I

1

2

3

4

5

6

Full height atrium


27

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)

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

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

9000 90009000 9000

7500

7500

9000 Atrium

LiftsStairs

ToiletZone

Void Lobby200mm R CShear walls

Building B - Structural drawings

Flat Slab1. 325mm concrete flat slab to upper floors and roof.2. Concrete class C 32/40.3. High-yield reinforcement.4. Assumed design imposed loads: Roof: 0.75kN/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 (1) increase to 750mm for GF - 1st (2) increase to 3200mm for GF - 1st

325

600

150

325 mm RC slab

Services zone



1075

Structural drawings

]


28


PT Flat Slab1. 250mm post-tensioned concrete flat slab 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: 0.75 kN/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)


9000 90009000 9000

7500

7500

9000

All Columns500 x 500 (G-1)450 x 450 (1-R)

LiftsStairs

ToiletZone

Void

Atrium

Lobby200mm R CShear walls

250

600

1000

150

Services zone



Reinforcement

250mm Post-tensioned slab

PT duct

]


29

Void

7500

9000

7500

9000 9000

254 x146UB31

406 x 140 UB39

457

x191

UB67

457

x191

UB67

457

x191

UB67

457

x191

UB67

406 x 140 UB46

406 x 140 UB39

406 x 140 UB46

406 x 140 UB46

406 x 140 UB46

406 x 140 UB39

406 x 140 UB46

406 x 140 UB46

406 x 140 UB46

9000 9000

LiftsStairs

ToiletZone

Atrium


406

x140

UB46

406 x 140 UB46

457

x191

UB67

406 x 140 UB46 406 x 140 UB39

406 x 140 UB39 254 x 146 UB31

406 x 140 UB39

406 x 140 UB46 406 x 140 UB46

254 x 146 UB31

457

x191

UB67

406

x140

UB39

254

x146

UB31

254 x 146 UB31

406

x140

UB46

406 x 140 UB46

406 x 140 UB39

406 x 140 UB46

406 x 140 UB46

406

x140

UB46

457

x191

UB67

457

x191

UB67

457

x191

UB67

457

x191

UB67

406 x 140 UB46

406 x 140 UB39

406 x 140 UB46

406 x 140 UB46

406 x 140 UB46

C1 = 254 x 254 UC73

C2 = 305 x 305 UC97

C3 = 356 x 368 UC129

C2C2

C2

C3

C2C2

C3

C2

C3

C2C2

C3C2

C1

C2

C2 C3

C3


350 (min)

130

457 x 191 UB67

Services zone



A193 mesh

1.2mm ribdeck AL1087

150

800 (min)

Composite1. 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


Offices: 5.0kN/m2

5. Vertical dimensions: Slab: 130mm Services zone(1): 807mm(2) Floor zone = 1087mm

Ceiling/lighting: 150mm ≈ 1090mm Floor to ceiling: 2700mm (3)

Raised floor: 250mm Total: 4040mm (1) including downstand beams (2) increase to 950mm for GF - 1st (3) increase to 3200mm for GF - 1st

]


30

In-situ + Hollowcore1. 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


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)


A

A

9000 9000

All Columns450 x 450

ToiletZone

Stairs

Void

A A

A A

A

B

B

B

B

A

A

A

A

A

B

BB

B

9000 9000

LiftsAtrium


A A

A

A A

C

B B

A A

B B

Beam Schedule

A 600 x 600 R C Beam

B 600 x 250 R C Beam

C 600 x 425 R C Beam

7500

9000

7500

200

800(min)

600

Services zone



A142 mesh in 50mm (min) structural topping

250

150mmhollowcore

450 450

425

600

1150

600

350(min)

150

50

Typical edgebeam

600


]


31

PT Band Beams1. 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


Offices: 5.0kN/m2

6. Vertical dimensions: Slab: 225mm Services zone(1): 800mm(2) Floor zone = 1175mm Ceiling/lighting: 150mm Floor to ceiling: 2700mm (3)


225

325800(min)

Services zone



2500 (typical)

150

PT Duct

1175

350 (min)

All Columns800 x 800

550 x 2500 P TBeam (typical)

LiftsStairs

ToiletZone

Void

Atrium


550 x 1750 P Tedge beam

550 x 2750 P Tbeam

7500

7500

9000

9000 9000 9000 9000


]


32

Long-Span Composite1. 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


Offices: 5.0kN/m2

5. Vertical dimensions: Slab and decking: 130mm Services zone(1): 800mm(2) Floor zone = 1080mm Ceiling/lighting: 150mm Floor to ceiling: 2700mm (3)


130

Cellular beam457 x 191 UB67 +533 x 210 UB92

Services zone



800 (min)

A142 mesh1.2 mm ribdeck AL

1080710 (Typical)

150

406

x140

UB39

406 x 140 UB39

356

x127

UB33

533 x 210 UB82

610 x 229 UB101

610 x 229 UB101610 x 229 UB101

610 x 229 UB101

356

x127

UB33

406

x140

UB39

406

x140

UB39

406

x140

UB39

406

x140

UB39

406

x140

UB39

406

x140

UB39

Lifts

Stairs

Void

Lobby


Toilet

Zone

457

x191

UB67

+533

x210

UB92

457

x191

UB67

+533

x210

UB92

457

x191

UB67

+533

x210

UB92

457

x191

UB67

+533

x210

UB92

457

x191

UB67

+533

x210

UB92

457

x191

UB67

+533

x210

UB92

457

x191

UB67

+533

x210

UB92

457

x191

UB67

+533

x210

UB92

457

x191

UB67

+533

x210

UB92

457

x191

UB67

+533

x210

UB92

457

x191

UB67

+533

x210

UB92

457

x191

UB67

+533

x210

UB92

406

x140

UB39

533 x 210 UB82 533 x 210 UB82 533 x 210 UB82 533 x 210 UB82

610 x 229 UB101

533 x 210 UB82

7500

7500

9000

9000 90009000 9000

Atrium

C3

C3

C1

C2 C3 C3 C3 C3

C3C3C4

C4C3 C3

C1 = 254 x 254 UC73

C2 = 305 x 305 UC97

C3 = 356 x 368 UC129

C4 = 356 x 368 UC177

610 x 229 UB101


]


33

Steel + Hollowcore1. 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


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)


350 (min)

250

533 x 210 UB82

Services zone



A142 mesh in 50 mm (min) structural topping

200 mm Hollowcore

1283

150

800 (min)

9000 90009000 9000

533 x 210 UB82

406

x140

UB46

406

x140

UB46

457 x 191 UB82

457 x 191 UB67 457 x 191 UB67 457 x 191 UB67 457 x 191 UB67

406

x140

UB39

406

x140

UB39

7500

7500

254 x146

UB31

203

x133

UB25

203

x133

UB25

203

x133

UB25

203

x133

UB25

203

x133

UB25

203

x133

UB25

203

x133

UB25

203

x133

UB25

533 x 210 UB82 533 x 210 UB82 533 x 210 UB82

9000

Lifts

Stairs

ToiletZone

Void

Atrium


406 x178

UB54

406

x178

UB60

457 x 191 UB82

533

x210

UB101

406 x 178UB54

457 x 191 UB67

533

x210

UB101

406 x 178 UB54

305 x 165UB40

457

x191

UB67

457 x 191 UB67

457 x 191 UB67

406 x 178 UB54

533

x210

UB82

457 x 191 UB67 457 x 191 UB67

406

x178

UB60

C1 C3

C3

C3

C3 C4

C4

C3

C2 C2

C3 C3

C3C3

C2

C3 C3

C2

C1 = 305 x 305 UC97

C2 = 305 x 305 UC158

C3 = 356 x 368 UC129

C4 = 356 x 368 UC153


]


34


Slimdek1. 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


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)


342

600

150

SD225 Deep decking

Services zone



1092

In situ concrete slab

300 ASB 249

A193 mesh

203

x102

UB23

203

x102

UB23

Atrium

300 ASB196

300 ASB196

300 ASB155

300

ASB249

203

x102

UB23

300 ASB249

300 ASB249

280

ASB74

280

ASB74

203

x102

UB23

9000

300 ASB249 300 ASB249 300 ASB249

9000 90009000

300 ASB249300 ASB249300 ASB249

203

x102

UB23

203

x102

UB23

300

ASB249

300

ASB155

203

x102

UB23

Void

300 ASB249280 ASB124

280ASB74

300 ASB249

203

x102

UB23

280 ASB74

300 ASB153

280 ASB74

300

ASB155

280

ASB74

Stairs

ToiletZone

Lobby

300 ASB153


280 ASB124

Lift

C1

C1 C1

C1C1

C2 C2 C2

C2

C2

C2 C2

C2

C2

C2 C2 C2

C2

7500

7500

9000

C1 = 305 x 305 UC97

C2 = 356 x 368 UC129

]


35

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.

Structuraloption

Procurementtime (weeks)

Lead time (weeks)

Overall construction time (weeks)

Frame construction time (weeks)

Overallproject

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

Building B

PT Flat Slab 10 6 66 17 82

Flat Slab 10 6 67 18 83

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 sub-contracting.

Building AThe 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.

Procurement programme

Lead times

NoteFrame construction time for

Composite, Steel + Hollowcore, Slimdek and

Long-Span Composite options includes construction of concrete jump-form core.


36

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, fi ve weeks for manufacture and one week for mobilisation.

Building BThe 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 elementsWith regard to lead times, the most critical element is cladding, which is required rela-tively 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 fi nancial risk of such a commitment to the cladding manufacturer.

The early appointment of a contractor under a two-stage tender approach can prove effec-tive in overcoming the problem and may also prove benefi cial 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 diffi culty; 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.


37

Programmes

Assumptions and logicA fi ve-day week was assumed. Holidays have not been shown on the programme and no allowance has been made for inclement weather. A simplifi ed 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 site-specifi c 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 fl oor 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 fl oor slab is constructed, thus saving time on the critical path, many steelwork contractors prefer the ground fl oor slab to be installed, as it is safer for the steelwork erectors to work from mobile elevated working platforms positioned on a fl at 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 fl oor slab is con-structed, the columns being cast from pile caps and the ground fl oor 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 long-lead 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 soffi t would permit greater use of prefabrication in the M&E services distribu-tion, with consequent programme savings, no allowance has been made for any reduction in the construction programme as a result of this potential benefi t.

Building AThe 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 48-week period for each of the buildings constructed using the Composite, Steel + Hollowcore and Slimdek options.

Building BOf 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.

Construction programmes


38

Building A - Programmes

Construction programmes Building A

Testing & commissioning

2Substructures Superstructure Roof finishes Roof installations External envelope Cores and risers Toilet fit-out M & E first fix M & E second fix Lifts Fit-out first floor Fit-out second floor Fit-out ground floor Final fix

External works

Activity

Week number

0 10 20 30 40 50 60Composite — 48 weeks

Number of weeksEstablish site

88

1685

9859

1712

0 10 20 30 40 50 60

8

111313

12



External works

Activity

Week number

0 10 20 30 40 50 60Steel + Hollowcore — 48 weeks


78

1685

9859

1712

0 10 20 30 40 50 60

8

111313

12


39



External works

Activity

Week number

0 10 20 30 40 50 60Flat Slab — 50 weeks


108

1685

8859

1712

0 10 20 30 40 50 60

8

111313

12




External works

Activity

Week number

0 10 20 30 40 50 60Slimdek — 48 weeks


78

1685

9859

1712

0 10 20 30 40 50 60

8

111313

12


40




External works

Activity

Week number

0 10 20 30 40 50 60PT Flat Slab


118

1685

8859

1712

0 10 20 30 40 50 60

8

111313

12

— 51 weeks



External works

Activity

Week number

0 10 20 30 40 50 60In-Situ + Hollowcore — 52 weeks


135

1685

8859

1712

0 10 20 30 40 50 60

8

111313

12


41

Construction programmes Building B

Building B - Programmes


Substructures Superstructure Roof finishes Roof installations Atrium glazing External envelope Cores and risers Toilet fit-out M & E first fix M & E second fix Lifts Fit-out first floor Fit-out second floor Fit-out third floor

Final fix

External works

Activity

Week number

0 10 20 30 40 50 60 70

0 10 20 30 40 50 60 70

Steel + Hollowcore — 65 weeks


219

201410

10

Fit-out fourth floor Fit-out fifth floor

1712

15

15

18

22

1915

2

1010101012



Final fix

External works

Activity

Week number

0 10 20 30 40 50 60 70

0 10 20 30 40 50 60 70

Slimdek — 65 weeks


219

201410

10


1812

15

15

18

22

1915

2

1010101012


42




Final fix

External works

Activity

Week number

0 10 20 30 40 50 60 70

0 10 20 30 40 50 60 70

PT Band Beams — 66 weeks


179

201410

10


1912

16

15

20

22

1919

2

1010101012



Final fix

External works

Activity

Week number

0 10 20 30 40 50 60 70

0 10 20 30 40 50 60 70

PT Flat Slab — 66 weeks


179

201410

10


1912

16

15

20

22

1919

2

1010101012


43



Final fix

External works

Activity

Week number

0 10 20 30 40 50 60 70

0 10 20 30 40 50 60 70

Composite — 67 weeks


239

201410

10


1712

15

15

19

22

1918

2

1010101012




Final fix

External works

Activity

Week number

0 10 20 30 40 50 60 70

0 10 20 30 40 50 60 70

Flat Slab — 67 weeks


189

201410

10


1916

16

15

25

22

1917

2

1010101012


44




Final fix

External works

Activity

Week number

0 10 20 30 40 50 60 70

0 10 20 30 40 50 60 70

Long-Span Composite


239

201410

10


1712

15

15

19

22

1917

2

1010101012

— 67 weeks



Final fix

External works

Activity

Week number

0 10 20 30 40 50 60 70

0 10 20 30 40 50 60 70

In-Situ + Hollowcore — 70 weeks


229

201410

10


1812

16

15

22

22

1919

2

1010101013


45

Summary of costs

7. Summary of costs

Basis of pricingPrices 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.

PreliminariesThe 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 fi xed 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 pro-gramme duration and the sequencing of operations within the programme. Adjustment of these costs has been made to refl ect the different construction durations identifi ed 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 costsThe study did not include assessment of the costs of fi nancing the project, nor consideration of return on rentals.

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

Costs


46

Summary of costs - Building A

Building A4642 m2 GIFA

Element Short-span optionsFlat Slab Composite In-situ + Hollowcore 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 fl oors 564,827 568,078 591,645 642,599 643,704 872,208

Roof fi nishes 241,208 241,208 241,208 241,208 241,208 241,208

Stairs 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 fi nishes 51,010 50,040 49,684 48,820 52,240 50,240

Floor fi nishes 274,432 274,432 274,432 274,432 274,432 274,432

Ceiling fi nishes 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

Mechanical 1,285,834 1,311,551 1,285,834 1,285,834 1,311,551 1,285,834

Electrical 637,811 650,567 637,811 637,811 650,567 637,811

Lifts 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 profi t 383,505 385,646 388,175 388,190 392,840 402,995

TOTAL £6,775,263 £6,813,088 £6,857,765 £6,858,021 £6,940,180 £7,119,578

Element Short-span optionsFlat Slab Composite In-situ + Hollowcore PT Flat Slab Steel + Hollowcore Slimdek

£/m2 % £/m2 % £/m2 % £/m2 % £/m2 % £/m2 %Substructure 43 2.9 41 2.8 44 3.0 43 2.9 42 2.8 41 2.7

Frame/upper fl oors 122 8.3 122 8.3 127 8.6 138 9.4 139 9.3 188 12.3

Roof fi nishes 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 fi nishes 11 0.8 11 0.7 11 0.7 11 0.7 11 0.8 11 0.7

Floor fi nishes 59 4.1 59 4.0 59 4.0 59 4.0 59 4.0 59 3.9

Ceiling fi nishes 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

Sanitary 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 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

Overheads and profi t 83 5.7 83 5.7 84 5.7 84 5.7 84 5.7 88 5.7

TOTAL £1,460 £1,468 £1,477 £1,477 £1,495 £1,534


47

Element Short-span options Long-span options Short-span options

Flat Slab PT Flat Slab Composite In-situ + Hollowcore

PT Band Beams Long-Span Composite

Steel + Hollowcore

Slimdek

Element total (£)

Element total (£)

Element total (£)

Element total (£)

Element total (£)

Element total (£)

Element total (£)

Element total (£)

Substructure 891,672 865,937 815,468 885,169 907,622 848,868 860,967 852,231

Superstructure 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 fi nishes 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 fi nishes 234,455 229,931 256,770 233,226 227,825 241,566 264,162 263,112

Floor fi nishes 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 fi nishes 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

Lifts 600,000 600,000 600,000 600,000 600,000 600,000 600,000 600,000

BWIC 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

Overheads and profi t 1,563,641 1,565,717 1,577,693 1,579,401 1,597,694 1,599,707 1,618,771 1,640,869

TOTAL £27,624,328 £27,660,993 £27,872,572 £27,902,748 £28,225,936 £28,261,499 £28,598,289 £28,998,690

Building B16,480 m2 GIFA

Element Short-span options Long-span options Short-span options

Flat Slab PT Flat Slab Composite In-situ + Hollowcore

PT Band Beams Long-Span Composite

Steel + Hollowcore

Slimdek

£/m2 % £/m2 % £/m2 % £/m2 % £/m2 % £/m2 % £/m2 % £/m2 %Substructure 54 3.2 53 3.1 49 2.9 54 3.2 55 3.2 52 3.0 52 3.0 52 2.9

Superstructure 110 6.6 122 7.2 114 6.7 112 6.6 135 7.9 134 7.7 138 7.9 183 10.3

Roof fi nishes 33 2.0 33 2.0 33 1.9 33 1.9 33 1.9 33 1.9 33 1.9 33 1.9

Stairs 8 0.5 8 0.5 8 0.5 8 0.5 8 0.5 8 0.5 8 0.5 8 0.5

External cladding 361 21.5 355 21.0 362 21.3 367 21.6 369 21.5 362 21.0 377 21.6 363 20.5

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 fi nishes 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 fi nishes 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 fi nishes 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

Overheads and profi t 95 5.7 94 5.7 95 5.7 95 5.7 97 5.7 97 5.7 98 5.7 99 5.7

TOTAL £1,676 £1,678 £1,691 £1,693 £1,713 £1,715 £1,735 £1,759

Summary of costs - Building B


48

Summary of costs

Key ratesKey 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 fl oor 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 soffi ts 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 – £1,545

Core walls SHS steel bracing tonne £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

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

Other element Unit Building A Building B

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

Internal planning

Non-structural dry-lined metal stud partitions m2 £55 £65

Blockwork walls to retail units m2 – £80


49

Study fi ndings

8. Study fi ndings

Building A – 3 storeyIn 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 storeyIn 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.

OverallThe most signifi cant 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 fl oors are considered, the Slimdek option was found to be between 54.1% and 66.4% more expensive than the most economic option.

Building AWith 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 BWith regard to speed of construction, for the short-span options in Building B, the con-struction 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:

Costs

Programme


50

Study fi ndings

Building A – short-span Building B – short-span Building B – long-spanFlat Slab 64 weeks PT Flat Slab 82 weeks PT Band Beams 83 weeks

PT Flat Slab 65 weeks Flat Slab 83 weeks Long-Span Composite 95 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 fi ndings 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 fl oor 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 fl oor costs’ are sub-divided into concrete frame, formwork and reinforce-ment, steel frame, decking & slabs and fi re protection.

(Minor differences between the fi gures used in the Study fi ndings and the Summary of costs are

due to rounding.)

Building A

Internal Planning

2%

Substructure 3%

Frame and Upper Floors10%

Preliminaries11%

Contingency & O/h&P

12%

External Cladding17%

M&E, Lifts & BWIC34%

Roof Finishes & Internal Finishes

11%

Average Elemental Breakdown

Building B

Internal Planning

1%

Substructure 3%

Frame and Upper Floors

8%Preliminaries

12%

Contingency & O/h&P

11%

External Cladding21%

M&E, Lifts & BWIC34%

Roof Finishes & Internal Finishes

10%

Average Elemental Breakdown


51

Study fi ndings - Building A

Overall costs

£/m2 % difference

Flat Slab £1,460 -

Composite £1,468 +0.5%

In-situ + Hollowcore £1,477 +1.2%

PT Flat Slab £1,477 +1.2%

Steel + Hollowcore £1,495 +2.4%

Slimdek £1,534 +5.1%

Overall costsBased on the building footprints and outline specifi cations 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 signifi cance 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 fi gure and table, the Slimdek option was found to be 5.1% more expensive than the Flat Slab option, with both options providing clear, unimpeded soffi ts.

These fi gures 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.

Study fi ndings – Building A

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.

PT Fl

at S

lab

1550

1525

1500

1475

1450

1425

1400

Flat

Sla

b

In-s

itu +

Hol

low

core

Com

posit

e

Stee

l +H

ollo

wco

re

Slim

dek

£/m²

Ove

rall

cons

truc

tion

cost

s


52

Element Substructures Frame and upper fl oors

Percentage of total cost 3% 10%

Findings Foundations for the three-storey building are simple pads. Costs for the ground-fl oor 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 fl oors 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 signifi cant feature is the premium required to achieve a clear, fl at soffi t with the Slimdek system as opposed to with alternative fl at soffi t 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 infi ll 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 benefi cial in informing the structural choice.

Relative costs

Percentage comparison with Flat Slab option


Note for frame and

upper fl oors

*Stairs have been

excluded from the

comparison, being of

equal cost for all

solutions.

45 40 35 30 25 20 15 10 5 0

Flat

Sla

b

In-s

itu +

Hol

low

core

PT Fl

at S

lab

Com

posit

e

Stee

l +H

ollo

wco

re

Slim

dek

£/m²

GF slabFoundationsEarthworks

Table 1Elemental cost

comparison.

180

160

140

120

100

80

60

40

20

0

Flat

Sla

b

In-s

itu +

Hol

low

core

PT Fl

at S

lab

Com

posit

e

Stee

l +H

ollo

wco

re

Slim

dek

£/m²

Fire protectionDecking & slabsSteel frame

FormworkReinforcementConcrete frame

Substructure costs

£/m2 % difference

Composite £41 -

Slimdek £41 -

Steel + Hollowcore £42 +2.4%

Flat Slab £43 +4.9%

PT Flat Slab £43 +4.9%

In-situ + Hollowcore £44 +7.3%

Frame and upper fl oors costs

£/m2 % difference

Flat Slab £122 -

Composite £122 -




Slimdek £188 +54.1%

*


53

External cladding Internal planning

17% 2%

For the costs of external cladding (curtain walling to main elevations and atrium, together with rain screens, brise-soleil, 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 signifi cant for this element.

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.

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

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.

This cost range refl ects the adjustment of the imbalance relating to the infi ll to steel braced cores, referred to in the Frame and upper fl oors element.

Account has been taken in the costing of the added complexity of fi re and acoustic sealing of partition heads against the irregular soffi ts of steel decking and around irregularly shaped intersecting steel frame members.


External cladding costs

£/m2 % difference

PT Flat Slab £215 -


Slimdek £219 +1.9%

Composite £219 +1.9%



Internal planning costs

£/m2 % difference

PT Flat Slab £30 -

Flat Slab £30 -


Slimdek £33 +10.0%



225

220

215

210

205

200

Flat

Sla

b

In-s

itu +

Hol

low

core

PT Fl

at S

lab

Com

posit

e

Stee

l +H

ollo

wco

re

Slim

dek

£/m²

35

30

25

20

15

10

5

0

Flat

Sla

b

In-s

itu +

Hol

low

core

PT Fl

at S

lab

Com

posit

e

Stee

l +H

ollo

wco

re

Slim

dek

£/m²

DoorsAtrium glazingInternal planning

Note for external

cladding

** Undercroft treatment

has been excluded from

the comparison, being of

equal cost for all

solutions.

**


54

Element Roof fi nishes and internal fi nishes, fi xtures and fi ttings

Mechanical and electrical services


Findings The costs of the roof fi nishes were the same across all the structural options, as is also the case for the fi xtures and fi ttings.

Slight differences in internal fi nishes costs are entirely contained within the wall fi nishes and refl ect 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 fi gures.

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 and Steel + Hollowcore options.

Relative costs



Table 1 cont’dElemental cost

comparison.

100

80

60

40

20

0

£/m²

Ceiling finishes Floor finishesWall finishes

Flat

Sla

b

In-s

itu +

Hol

low

core

PT Fl

at S

lab

Com

posit

e

Stee

l +H

ollo

wco

re

Slim

dek

Finishes costs

£/m2 % difference

PT Flat Slab £97 -

In-situ + Hollowcore £97 -

Composite £97 -

Slimdek £97 -

Flat Slab £97 -

Steel + Hollowcore £97 -

Mechanical and electrical costs

£/m2 % difference

Flat Slab £512 -



Slimdek £512 -



550 500 450 400 350 300 250 200 150 100 50

0

Flat

Slab

In-s

itu +

Hol

low

core

PT Fl

at Sl

ab

Com

posit

e

Stee

l +H

ollo

wco

re

Slim

dek

£/m²

BWCLifts

MechanicalSanitary

Electical

Note for fi nishes *Roof fi nishes and

fi xtures and fi ttings

have been excluded

from the comparison,

being of equal cost for

all solutions.

*


55

Preliminaries Contingency, overheads and profi t

11% 12%

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

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 refl ect the different construction durations between 48 and 52 weeks identifi ed 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.

A design contingency of 7.5% has been included within the budget costs, to refl ect 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 profi t. 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 fl oors on the most economic solutions.


Preliminaries costs

£/m2 % difference

Composite £154 -


Slimdek £154 -




Contingency, overheads and profi t costs

£/m2 % difference

Flat Slab £168 -





Slimdek £177 +5.4%

180

160

140

120

100

80

60

40

20

0

Overheads & profitContingency

£/m²

Flat

Slab

In-s

itu +

Hol

low

core

PT Fl

at Sl

ab

Com

posit

e

Stee

l +H

ollo

wco

re

Slim

dek

180

160

140

120

100

80

60

40

20

0

Time-related preliminariesFixed preliminaries

£/m²

Flat

Sla

b

In-s

itu +

Hol

low

core

PT Fl

at S

lab

Com

posit

e

Stee

l +H

ollo

wco

re

Slim

dek


56

Overall costs

Based on the building footprints and outline specifi cations 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 signifi cance 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 fi gure 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 soffi ts.

These fi gures 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.

Study fi ndings - Building B

1750

1725

1700

1675

1650

1625

1600

PT B

and

Beam

s

Long

span

Com

posit

eLong spanShort span

£/m²

£/m²

Flat

Sla

b

In-s

itu +

Hol

low

core

PT Fl

at S

lab

Com

posit

e

Stee

l +H

ollo

wco

re

Slim

dek

Study fi ndings – Building B

Overall costs£/m2 % difference

Flat Slab £1,676 -

PT Flat Slab £1,678 +0.1%

Composite £1,691 +0.9%

In-situ + Hollowcore £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%

Ove

rall

cons

truc

tion

cost

s


57


Element Substructures Frame and upper fl oors


Findings Foundations for Building B are piled, with varying pile depths, pile cap sizes and confi gurations for each option. Costs for the ground fl oor slab and associated earthworks are identi-cal 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%.

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.

When the costs of the frame and upper fl oors only are com-pared, the most economic option is the Flat Slab, with costs for the alternative structural options ranging from +1.8% to +66.4%. A signifi cant feature is the premium required to achieve a clear, fl at soffi t with the Slimdek system as opposed to with alternative fl at soffi t solutions, the Flat Slab and PT Flat Slab options. This is shown graphically and in tabular form below.

For the long-span options, the frame and upper fl oors 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.

Relative costs

Percentage comparison with Flat Slab option Substructure costs

£/m2 % difference

Composite £49 -

Slimdek £52 +6.1%





Long-Span Composite £52 +6.1%

PT Band Beams £55 +12.2%

Table 2Elemental cost

comparison.

605550454035302520151050

Flat

Sla

b

In-s

itu +

Hol

low

core

PT Fl

at S

lab

Com

posit

e

Stee

l +H

ollo

wco

re

Slim

dek

PT B

and

Beam

s

Long

Spa

nCo

mpo

site

£/m²

GF slabFoundationsEarthworks

Frame and upper fl oor costs£/m2 % difference

Flat Slab £110 -





Slimdek £183 +66.4%



Note for frame and

upper fl oors

*Stairs have been

excluded from the

comparison for clarity,

being of equal cost for

all solutions.

200

180

160

140

120

100

80

60

40

20

0

£/m²

Fire protectionDecking & slabsSteel frame

FormworkReinforcementConcrete frame

Flat

Sla

b

In-s

itu +

Hol

low

core

PT Fl

at S

lab

Com

posit

e

Stee

l +H

ollo

wco

re

Slim

dek

PT B

and

Beam

s

Long

Spa

nCo

mpo

site

*


58

Element External cladding Internal planning


Findings For the costs of external cladding (curtain walling to main elevations and atrium, together with rainscreens, brise-soleil, 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 signifi cant for this element.

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.

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

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, In-situ + Hollowcore, Slimdek and Long-Span Composite options. As with Building A, the costing takes account of the added complexity of fi re and acoustic sealing of partition heads against the irregular soffi ts of steel decking and around irregularly shaped intersecting steel frame members. The effect of this factor on Building B is more signifi cant due to the quantity of blockwork walls within the ground fl oor retail space.

Such a large cost range refl ects 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.

Relative costs



External cladding costs£/m2 % difference




Slimdek £363 +2.3%






comparison.

375

365

355

345

335

325

£/m²

Flat

Sla

b

In-S

itu +

Hol

low

core

PT Fl

at S

lab

Com

posit

e

Stee

l +H

ollo

wco

re

Slim

dek

PT B

and

Beam

s

Long

Spa

nCo

mpo

site

Internal planning costs£/m2 % difference

PT Flat Slab £18 -

Flat Slab £18 -



Slimdek £22 +22.2%


PT Band Beams £18 -


25

20

15

10

5

0

Flat

Sla

b

In-S

itu +

Hol

low

core

PT Fl

at S

lab

Com

posit

e

ISte

el +

Hol

low

core

Slim

dek

PT B

and

Beam

s

Long

Spa

nCo

mpo

site

£/m²

DoorsInternal planning


59

Roof fi nishes and internal fi nishes, fi xtures and fi ttings


10% 33%

The costs of the roof fi nishes were the same across all the structural options and they are therefore not included in the comparison of the internal fi nishes shown graphically and in tabular form below, which is also the case for the fi xtures and fi ttings.

For the internal fi nishes (fl oor wall and ceiling fi nishes) 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.

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

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.


60055050045040035030025020015010050

0

Flat

Slab

In-s

itu +

Hol

low

core

PT Fl

at Sl

ab

Com

posit

e

Stee

l +H

ollo

wco

re

Slim

dek

PT B

and

Beam

s

Long

Span

Co

mpo

site

£/m²

BWCLifts

MechanicalSanitary

Electical

140

120

100

80

60

40

20

0

Com

posit

e

Stee

l +H

ollo

wco

re

Slim

dek

PT B

and

Beam

s

Long

Spa

nCo

mpo

site

£/m²

Ceiling finishes Floor finishesWall finishes

Flat

Sla

b

In-s

itu +

Hol

low

core

PT Fl

at S

lab

Finishes costs£/m2 % difference






Slimdek £129 +1.6%



Mechanical and electrical costs£/m2 % difference

Flat Slab £562 -



Slimdek £562 -





Note for fi nishes *Roof fi nishes and

fi xtures and fi ttings

have been excluded

from the comparison

for clarity, being of

equal cost for all

solutions.

*


60


Element Preliminaries Contingency, overheads and profi t


Findings The budget for preliminaries for each option was based on two separate elements. A lump sum to allow for both non-work-related aspects, such as contractual requirements for insurances, employer’s facilities, etc., together with fi xed 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 therefore vary according to programme duration and the sequencing of operations within the programme. Adjustment of these costs has been made to refl ect the different construction durations between 65 and 70 weeks identifi ed 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.

A design contingency of 7.5% has been included within the budget costs, to refl ect 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 profi t. 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.

Relative costs

Percentage comparison with Flat Slab option Preliminaries costs

£/m2 % difference

Slimdek £199 -









comparison.

200

180

160

140

120

100

80

60

40

20

0

Flat

Slab

In-s

itu +

H

ollo

wco

re

PT Fl

at Sl

ab

Com

posit

e

Stee

l +H

ollo

wco

re

Slim

dek

PT B

and

Beam

s

Long

Span

Com

posit

e

£/m²

Overheads & profitContingency

200

180

160

140

120

100

80

60

40

20

0

Flat

Sla

b

In-s

itu +

H

ollo

wco

re

PT Fl

at S

lab

Com

posit

e

Stee

l +H

ollo

wco

re

Slim

dek

PT B

and

Beam

s

Long

Spa

n Co

mpo

site

Time-related preliminariesFixed preliminaries

220

£/m²

Contingency, overheads and profi t costs£/m2 % difference

Flat Slab £191 -





Slimdek £202 +5.8%




61

Study fi ndings

It is evident from the study fi ndings presented that the effects of the choice of a parti-cular structural solution do not arise solely within the Frame and upper fl oors 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 fi ndings above.

Summary comparison charts

Building B Flat Slab PT Flat Slab Composite In-situ + Hollowcore

PT Band Beams

Long-Span Composite

Steel + Hollowcore

Slimdek

Substructure

Base

cas

e fo

r com

paris

on

–2.9% –8.5% –0.7% +1.8% –4.8% –3.4% –4.4%

Frame and upper fl oors +10.9% +3.6% +1.8% +22.7% +21.8% +25.5% +66.4%

External cladding –1.7% +0.1% +1.7% +2.3% +0.1% +4.3% +0.4%

Internal planning –1.1% +19.7% +1.1% +1.4% +19.7% +23.4% +20.0%

Wall fi nishes –1.9% +9.5% 12.7% –2.8% +3.0% +12.7% +12.2%

M and E, lifts and BWIC

0% +1.4% 0% 0% +1.4% +1.4% 0%

Contingency +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%

Overheads and profi t

+0.1% +0.9% +1.0% +2.2% +2.3% +3.5% +4.9%

Building A Flat Slab Composite In-situ + Hollowcore

PT Flat Slab Steel + Hollowcore

Slimdek

Substructure

Base

cas

e fo

r com

paris

on

–4.9% +1.6% +0.5% –2.0% –3.7%

Frame and upper fl oors +0.6% +4.1% +13.1% +13.9% +54.1%

External cladding +0.8% +2.1% –1.1% +3.3% +0.9%

Internal planning +10.0% +3.3% 0% +13.3% +10.0%

Wall fi nishes –1.9% –2.6% –4.3% +2.4% –1.5%

M and E, lifts and BWIC

+1.6% 0% 0% +1.6% 0%

Contingency +1.0% +1.0% +1.2% +3.1% +6.1%

Time-related preliminaries

–3.9% +3.9% +2.0% –3.9% –3.9%

Overheads and profi t

+0.6% +1.2% +1.2% +3.0% +5.4%


62

Commentary from The Concrete Centre

9. Commentary from The Concrete Centre

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 offi ces, for both the three-storey 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 fi nishes, 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 propor-tion 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 diffi culties, site constraints, access, adjacent buildings, etc. that are particular to that project and will affect the preliminaries. Such aspects are intrinsically project specifi c and are therefore beyond the scope of the study.

There are no differences in the design or specifi cation 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.

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 post-tensioned 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 infi ll within the elemental summaries in order to achieve a like-for-like comparison, the frames and upper fl oors 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.

Foundations

Main conclusion

Differences in cost

Frame and upper fl oors


63


It should be appreciated that in most cost plans, the infi ll 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. Conse-quently any comparison of the costs of the frame and upper fl oors only could be distorted by a signifi cant amount.

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 fl oor-to-fl oor height is almost always achieved with a fl at soffi t and separate services zone, offering the potential for additional storeys in high-rise buildings and thus improved rental or sales return. Smaller fl oor-to-fl oor heights have reduced cladding areas and hence lowered costs, and of increasing importance is the potential benefi t that a reduced cladding area has on the building’s energy use.

It should be noted that a premium is incurred in sealing and fi re stopping at partition heads against profi led soffi ts 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 benefi ts associated with the potential for fabric energy storage. Nonetheless, it should be noted that the removal of suspended ceilings in order to benefi t 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 ventilationBoth 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.

FlexibilityA fl at soffi t 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 fl exibility in design and allows co-ordination effort to be focused elsewhere. Services installation is simplest below a fl at soffi t, permitting maximum off-site fabrication of services, higher quality of work and quicker installation.

Internal planning

External cladding



64


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 benefi ts in the form of reduced maintenance downtime due to ease of equipment change-out, greater fl exibility and less disruption to an occupier’s business operations.

Flat soffi ts 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 benefi ts are some of the main reasons for the development of Slimdek; however, this study shows the signifi cant 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, fl at soffi t.

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 fl oor area, and this fi nding is still valid.

General conclusionsThe lead times for the Flat Slab, In-situ + Hollowcore, PT Flat Slab and PT Band Beam options are signifi cantly 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-fl oor level and commence the walls and columns from the fourth to fi fth fl oor, 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.

Nett lettable area

Programmes


65


Construction programmesThe programmes refl ect 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 infl uenced 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 benefi cial, as the work can be let before the design of following packages has been fi nalised.

The programmes prepared for this study refl ect 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 profi le 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-specifi c. 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 fi re protection used to be a critical activity, modern details such as site-applied intumescent coating have removed fi reproofi ng from the critical path altogether. However, although not on the critical path, the fi reproofi ng activity requires a greater level of detailing and causes disruption that can adversely affect other trades, e.g. diffi culties caused by fi xings penetrating through fi re-proofi ng and damage needing rectifi cation.

Off-site intumescent coatings have been introduced in an effort to reduce the construction time, but these can suffer from signifi cant damage in transit, requiring site remedial work which can eliminate the original saving.

The durations of fi rst fi x, second fi x 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 fl at soffi ts 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.


66


Although the reported costings excluded the effects of fi nance costs, if fi nance costs were to be considered, they should not be limited to the construction period alone as, in most cases, fi nance costs also affect the procurement and lead times.

It is not possible to examine the entire project from inception to completion, as the dura-tion prior to the commencement of procurement cannot be defi ned on a generic basis. However, consideration of the periods that have been identifi ed in the programmes for pro-curement, 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.

Finance costs

Building B Flat Slab PT Flat Slab

Composite In-situ + Hollowcore

PT Band Beams

Long-Span Composite

Steel + Hollowcore

Slimdek

Construction cost in £/m2 £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 fi nance 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

Building A Flat Slab Composite In-situ + Hollowcore

PT Flat Slab Steel + Hollowcore

Slimdek

Construction cost in £/m2 £1,460 £1,468 £1,477 £1,477 £1,495 £1,534

Overall programme in weeks 64 70 66 65 70 70

Savings in fi nance costs @ 7.75% p.a. +£0 +£5 +£2 +£1 +£5 +£5

£1,460 £1,473 £1,479 £1,478 £1,500 £1,539

This comparison takes no account of differences in cumulative fi nance costs arising from the different cash fl ow profi les 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 fl ow profi les would be required in order to present a detailed comparison of these effects on fi nance costs.

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 briefl y considered in more detail below.

Overall value vs frame costFrame 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 confi dent that the optimum structural solution has been selected.

Other value considerations


67


Fire protectionFor Flat Slab, In-situ + Hollowcore, PT Flat Slab and PT Band Beam structures, fi re protection is generally not needed, as the material has inherent fi re resistance of up to four hours. This removes the time, cost and separate trades required for fi re protection. Added value bene-fi ts 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 fi re.

Exposed soffi tPotential value to a client exists in those structures with a high thermal mass. By exposing the soffi ts, 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 benefi ts and reduced lifetime maintenance costs.


68

Appendix A - Detailed programmes

10. Appendix A – Detailed programmes

Project

Dated Drawn by Programme No

Title

Revision comment

Notes

ProgrammeTitle

Client

COMMERCIAL BUILDINGS - COST MODEL STUDYBuilding A : Scheme 1 - Flat Slab

The Concrete Centre 11/07/2006 rev

Line Name 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 50 511

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

Site Set Up

SubstructureRemove Topsoil & RL DigPad FoundationsUnderslab DrainageGround Floor Slab

SuperstructureWalls / Columns Grd to 1st1st Floor SlabWalls / Columns 1st to 2nd2nd Floor SlabWalls / Cols 2nd to 3rd3rd Floor SlabRoof Upstands & Bases

Roof InstallationsRoof FinishesDeliver Main Roof PlantRoof MEP InstallationsInstall Plant Screen Louvres

Curtain Wallling/External CladdingSurvey/Set Out BracketsSecondry Steelwork/FramingGlazing & Spandrel PanelsCapping/Flashing & Roof Upstand Level

Building Watertight

Cores & RisersMEP RisersToilet Fit OutLift Installations

Office Fit Out to Cat ALevel 2H/L MEP 1st Installations

Suspended Ceiling Grid & Service Tiles

H/L MEP 2nd Fix

Raised Flooring

Joinery 1st Fix

Level 1Level G

Close Out

Testing & Commissioning

External Works

Completion

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

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

Line Name 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


69


Project


Title

Revision comment

Notes

ProgrammeTitle

Client

COMMERCIAL BUILDINGS - COST MODEL STUDYBuilding A : Scheme 4 - Composite


Line Name 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 48 491

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

Site Set Up

SubstructureRemove Topsoil & RL DigPad FoundationsUnderslab DrainageGround Floor Slab

SuperstructureSteelworkMetal DeckingRC ToppingRoof Upstands & Bases

Roof InstallationsRoof FinishesDeliver Main Roof PlantRoof MEP InstallationsInstall Plant Screen Louvres

Curtain Wallling/External CladdingSurvey/Set Out BracketsSecondry Steelwork/FramingGlazing & Spandrel PanelsCapping/Flashing & Roof Upstand Level

Building Watertight

Cores & RisersMEP RisersToilet Fit OutLift Installations



H/L MEP 2nd Fix

Raised Flooring

Joinery 1st Fix

Level 1Level G

Close Out


External Works

Completion

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

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

Line Name 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

Project


Title

Revision comment

Notes

ProgrammeTitle

Client

COMMERCIAL BUILDINGS - COST MODEL STUDYBuilding B : Scheme 1 - Flat Slab


Line Name 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 67 681

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

Site Set Up

SubstructurePile ProbingForm Pile MattPiled FoundationsExcavate & Form Pile CapsUnderslab DrainageGround Floor Slab

SuperstructureWalls / Columns Grd to 1st1st Floor SlabWalls / Columns 1st to 2nd2nd Floor SlabWalls / Cols 2nd to 3rd3rd Floor SlabWalls / Columns 3rd to 4th4th Floor SlabWalls / Cols 4th to 5th5th Floor SlabCols / Walls 5th to 6th Roof SlabRoof Upstands & Plant Bases

EnvelopeRoof FinishesRoof InstallationsAtrium GlazingCurtain Wallling/External Cladding

Building Watertight

Cores & RisersM&E RisersToilet Fit OutLift Installations


Perimeter Ceiling Plasterboard Margin


H/L MEP 2nd Fix

Raised Flooring

Joinery 1st Fix

Level 2Level 3Level 4Level 5

Close OutTesting & CommissioningExternal WorksCompletion

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

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

2d

Line Name 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


70


Project


Title

Revision comment

Notes

ProgrammeTitle

Client

COMMERCIAL BUILDINGS - COST MODEL STUDYBuilding B : Scheme 4 - Composite


Line Name 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 67 681

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

Site Set Up

SubstructurePile ProbingForm Pile MattPiled Foundations (128 No)Excavate & Form Pile CapsUnderslab DrainageGround Floor Slab

SuperstructureConcrete Core (jump form)Structural Steelwork Metal DeckingRC ToppingUpstands/Bases at Roof Level

EnvelopeRoof FinishesRoof InstallationsAtrium GlazingCurtain Wallling/External Cladding

Building Watertight

Cores & RisersM&E RisersToilet Fit OutLift Installations


Perimeter Ceiling Plasterboard Margin


H/L MEP 2nd Fix

Raised Flooring

Joinery 1st Fix

Level 2Level 3Level 4Level 5

Close Out


External Works

Completion

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

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

45d

Line Name 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


CC

IP-010C

ost Model Study – C

omm

ercial BuildingsA

report comm

issioned by The Concrete C

entre

Cost Model Study –Commercial BuildingsA comparative cost assessment of the construction of multi-storey offi ce buildings


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 offi ce building in an out-of-town location and a six-storey offi ce building in a city centre location. A total of 14 fl oor design options were evaluated, budget costings were assigned to all elements of construction and adjustments were made to refl ect 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 offi ce construction.

CCIP-010 Published October 2007 ISBN 1-904482-36-8Price Group P

© The Concrete Centre

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

CI/Sfb

UDC624.94.04.033

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


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