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    Office Cost Study

    COMPARING THE EFFECTS OF STRUCTURAL SOLUTIONS ON COST

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    Overview of the study 4

    Building designs and structural options 6

    Costs and programme data 9

    Cost comparison and conclusions 12

    Office Cost Study

    Contents

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    The Concrete Centre aims to assist all those who design and constructin concrete to realise the full potential of the material.To this end, The

    Concrete Centre undertakes independent research to identify, whennecessary, the true facts of building in concrete.A complete cost modelstudy was commissioned in order to compare the costs of constructingoffice buildings with different structural solutions, the results of which arepresented briefly in this summary document. For comprehensive analysisof the study, the complete report is available, details of which can befound below.

    The design teamThe success of any project depends on the skills and knowledge of thewhole design team.To harness the experience representative of a realproject, top practitioners in each field were represented in the study inorder to form a rounded view of the design. The cost model study was

    undertaken by staff from Allies and Morrison (architectural design); Arup(structural design); Davis Langdon (quantity surveying) and Mace(programming).The report was designed to be a fair comparison of costsfor two common-place office building types.The designs were selected togive no bias towards concrete solutions, for example, the proven benefitsof thermal mass were not considered.

    Further publicationsTo assist all members of a design team, The Concrete Centre produces arange of technical design guidance to enable effective concrete construction.Complementary documents that may be of interest as further reading arelisted below:

    Concrete Frame Elements - Intended as a pre-scheme designhandbook, this publication helps designers to choose the most viableconcrete options. Based on BS 8110, it includes cost-optimisedspan-to-depth charts for various types of in-situ, precast andpost-tensioned floor and beam construction over a range of spansand loads. Other information, such as preliminary column sizing andreinforcement estimates is included.

    Utilisation of Thermal mass in Non Residential Buildings - Thisguide provides detailed guidance on the use of thermal mass as a

    sustainable method of cooling which avoids or reduces the need for air conditioning.This publication should assist designers wishing to exploitthermal mass and includes chapters on concrete floor options,integration of services, acoustic considerations and surface finishoptions.The guide also includes a number of case studies.

    Cost Model Study School Buildings - This publication is parallel tothis study of office buildings and reports a comprehensive andindependent cost study which was undertaken to provide a comparisonbetween six structural frame options for a typical secondary school.Budget costings were assigned to all elements of construction andadjustments were made to reflect time-related costs attributable todifferences in the construction programme.

    For more information on these, and other publications from The ConcreteCentre, visitwww.concretecentre.com/publications

    The full technical report isavailable from The Concrete Centre.

    To purchase your copy visitwww.concretebookshop.comor call0700 4 607777

    Ref:CCIP-010Price:45

    Office Cost Study

    PAGE 3

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    The full Commercial Buildings Cost Model Study was undertaken to provide

    a comparison of the construction costs associated with building options.

    PurposeCost is a major criterion in assessing design and constructionalternatives, and construction professionals require current studiesin order to inform their decisions. However, the value of a cost study isoften found to be not so much in the cost results, but in the detailed andrigorous assessment of how structural frame choice can affect the cost of other items, such as cladding, internal planning, services, fit-out, etc.

    The Concrete Centre commissioned a commercial buildings cost modelstudy, which was designed to provide a detailed cost comparison. The factthat the study also acts as an independent assessment of current building

    types means that it will be of enduring value to quantity surveyors,architects, engineers and other construction professionals.

    This publication provides a brief overview of the findings. For moreinformation on the results found in this publication, please refer to thefull Cost Model Study - Commercial Buildings [1].

    MethodologyThe commercial buildings cost model study was undertaken in 2006 andcompared the costs of constructing three- and six-storey commercialbuildings, using a variety of short-span and long-span reinforced concreteand steel-frame options, taking into account construction, full fit-out, andthe effect of programme times on cost.

    The buildings were notionally located in two different locations an out-

    of-town business park and central London - and were based on appropriatestructural grids commonly in current use, with specifications suited tocontemporary market conditions.

    The designs were taken to normal outline design stage, the only differencesbeing directly attributable to the structural frame material. Budgetcostings were assigned to all elements of construction, from substructure,superstructure and external envelope through to preliminaries, with theexception of external works, which were considered to be too highlysite-specific to permit accurate costing. Adjustments were made to thecostings to reflect time-related costs attributable to differences inconstruction programmes.

    Whilst identifying the variation in the costs of frames, the studyalso considered the effects that the choice of framing material andmethod of construction had on other elements of the building,as well as the other benefits that the choice of frame can generate(see page 13).

    Overview of the study

    Office Cost Study

    PAGE 4

    Slimdek is a registered trademark of Corus UK Ltd.

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    ImpartialityThe study was undertaken on a completely independent basis by leadingpractitioners in their field:

    Allies and Morrison Architectural design Arup Structural design

    Davis Langdon LLPQuantity surveying Mace Programming

    The structural design for all options was carried out by Arup and costswere prepared by Davis Langdon, based on pricing data obtained fromthe practices national cost database of recent projects and, therefore,reflecting the current marketplace. The cost models were developed usingcurrent best practice for both concrete and steel as determined by theprofessional team.

    ConclusionsThe main interest in any cost model study is the process of designing

    and costing alternative methods of constructing otherwise identicalbuildings, as this raises many interesting issues for those commissioning,designing and constructing buildings.

    Overall, the results of the commercial buildings cost model study showedthat when developing modern commercial buildings, concrete-framedsolutions are highly competitive with steel-framed solutions and thestudy proves conclusively that construction costs for concrete are up to6% lower than for steel.

    However, the study also demonstrates the need to consider all elementsof the building cost, rather than simply the cost of the structure, andhighlights the extent to which elements other than the structure areaffected by the choice of frame solution (see Table 1). In particular,when the overall procurement and construction programme is considered,modern concrete-framed buildings CAN be procured and constructed ina shorter time frame (up to nearly 12% faster) than steel-framed buildings.Concrete-framed buildings can also offer a range of other added-valuebenefits at no extra cost, such as fire resistance, durability, robustness,safety and ease of service integration, making concrete the idealconstruction material for commercial buildings. By adding to this itsenergy efficiency, concrete truly deserves a position as the constructionmaterial of choice for new commercial buildings in the UK.

    Office Cost Study

    PAGE 5

    Proportion of overallconstruction cost (%)

    Variation dictated by structuralsolution, (% of package cost)

    Variation dictated by structuralsolution (/m )2

    Proportion of overallconstruction cost (%)

    Variation dictated by structuralsolution,

    Variation dictated by structuralsolution (/m )2

    Substructure ExternalCladding

    InternalPlanning

    Finishes M&E

    3

    7.3

    3

    3

    2.2

    6

    17

    4.2

    9

    21

    6.2

    22

    2

    13.3

    4

    1

    22.2

    4

    11

    -

    -

    10

    1.6

    2

    34

    1.6

    8

    33

    1.4

    8

    Prelims

    11

    5.2

    8

    12

    6

    12

    B u

    i l d i n g A

    B u

    i l d i n g B

    (% of package cost)

    Table 1: How much does the choice of structural solution affect the cost of other packages? *

    * Packages not affected by structural solution are not listed.Building A - three-storey 4,650m2 office in an out-of-town business park location. For flat slab solution: total construction cost 1,460 /m2, superstructure costs 122 /m2.Building B - six-storey 16,500m2 office in central London. For flat slab solution: total construction cost 1,676 /m2, superstructure costs 110 /m2.

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