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Cost breakdown of base scheme
 element cost £ cost/m2 gifa £% of total cost
Substructure 316,40044.563.55
200 thick ground slab, pad foundations, bases for external escape stairs
Frame and upper floors1,204,500169.6513.53
Insitu concrete frame; 500mm diameter insitu columns; 350mm thick suspended slabs to upper floors and roof; 250mm thick insitu concrete shear walls
Roof 293,40041.323.29
Flat roof finishes; high-performance two-layer felt roof membrane; metal decking and insulation; double-glazed atrium rooflight; rainwater goods and downpipes
Stairs and balustrades141,80019.971.59
Insitu concrete stairs; balustrades, handrails and walkways
External walls1,801,400253.7220.23
Aluminium stick and panel curtain walling system; aluminium rainscreen cladding on blockwork backing; limited solar shading; glazed partition to atrium
Internal partitions131,50018.521.48
Blockwork; WC cubicles   
Internal doors86,50012.180.97
Wall finishes117,30016.521.32
Plaster and paint; painted concrete   
Floor finishes507,70071.515.70
Raised floors in office areas; stone and tile finishes to landlord's areas 
Ceiling finishes227,00031.972.55
Mineral fibre suspended ceilings; plasterboard finish to landlord’s areas 
Furniture and fittings147,50020.771.66
Reception furniture, signage, artwork, blinds   
Sanitary appliances41,8005.890.47
Disposal installations40,8005.750.46
Water installations67,7009.540.76
Space heating and air treatment810,400114.149.10
Displacement ventilation system; air cooled chiller; AHU with heat reclaim; distribution; floor diffusers
Electrical installations512,10072.135.75
Mains, sub mains, power to mechanical services; lighting, landlord’s small power
Gas installations17,9002.520.20
Lift installation146,00020.561.64
Protective installations12,6001.770.14
Communication installations107,80015.181.21
Fire alarm, CCTV, security system   
Special installations126,70017.851.42
Builders’ work 68,0009.580.76
External works and services672,20094.687.55
Preliminaries, contingencies and OHP 1,305,000183.8014.67
Construction cost of base scheme8,904,0001,254.08100.00
Enhancements to scheme to achieve current best practice sustainability
 element cost £ cost/m2 gifa £% of total cost
ADD additional foundation and ground slab costs arising from increased footprint associated with two-storey design; pad foundations; 200 mm thick ground slab; below ground drainage. 2300 m2 @ £180
Base building substructure costs based on footprint area of 1636m2.
Extra over 200 mm thick ground floor slab for incorporation of recycled aggregates in concrete 1000 m3 @ £15
Below ground drainage pipes and fittings in clay in lieu of PVC 2300 m2 @ 0
Reduced use of potentially toxic materials at no overall increase in cost
Frame, upper floors and stairs849,500119.658.62
OMIT six-storey insitu concrete frame; upper floors and roof; insitu concrete shear walls 7100 m2 @ (£170)
ADD two-storey steel frame; universal columns and beams @ 50kg/m2; standard proprietary hollowcore precast concrete floor and roof deck units; finishes to steelwork – no fire protection required 7100 m2 @ £120
Embodied energy and transport benefits from utilising partially recycled steel and reduced cement volume; reduced building mass through use of hollow core units in lieu of insitu concrete; reduced waste due to off-site fabrication of steel and precast units; exposed thermal mass using PC units; reduced use of toxic materials as no fire protection required to steel due to adoption of fire-engineering-based design.
OMIT bespoke glazed rooflight over atrium to six-storey building 80 m2 @ (£750)
OMIT flat roof finishes to six-storey building; felt roof membrane on metal decking and insulation 1465 m2 @ (£116)
ADD northlight roof to two-storey building; secondary steelwork; standing seam mill finish aluminium; 175 mm zero ODP insulation to achieve good practice U-value 4465 m2 @ £80
Roof profile designed to increase natural daylighting. Operational lighting costs and lighting heat load will reduce as system is specified in conjunction with a lighting control system. Increased roof area due to replanning of building based on two storeys, and northlight profile. Actual roof area stated rather than plan area.
Extra over for roof installation for fan assisted ventilation shafts; refer to building services for costs of fans 42 @ £3250
Fan-assisted natural ventilation provided to supplement natural cross ventilation
ADD increased drainage requirements for increased area of roof for a two-storey building; siphonic drainage, gutters, outlets, pipework. 2935 m2 @ 12
ADD increased area of glazed rooflights; thermally broken patent glazing ; sealed double-glazed units 635 m2 @ £340
Increased natural daylighting to 100% of office space to BS8206. Operational lighting costs and lighting heat load will reduce as system is specified in conjunction with a lighting control system
Extra over for Argon filled cavity to rooflights; U-value = 1.4 W/m2K 635 m2 @ £30
Management of potentially increased heating and cooling loads resulting from increased U-value and improved thermal performance of rooflights
Extra over for opening vents to rooflights to assist natural ventilation; tilt and turn vents; actuator motors; refer to special installations for controls 84 @ £800
Reduced carbon emissions, running costs and plant replacement costs resulting from simplification of mechanical installation
ADD solar shading to rooflights; externally mounted, proprietary aluminium louvres 635 m2 @ £150
Management of increased solar heat load and glare resulting from increased area of roof lights
ADD for automated solar control blinds to rooflights; including interface with controls 635 m2 @£70
Management of increased solar heat load and glare resulting from increased area of rooflights
Extra for enhanced insulation thickness to roof to meet best practice U-values (overall thickness 200 mm); U-value = 0.18 W/m2K 4465 m2 @ £1.10
Extra over for insulation for achieving best practice U-value with 200 mm injected cellulose insulation (Warmcell 500) 4465 m2 @ £0.25
Extra for achieving same U-value with natural sheep’s wool insulation. 4465 m2 @ £8.15
Renewable source of materials   
ADD balustrading to first-floor voids 300 m @ £450  
OMIT reduced number of stairflights for two-storey building 24 (£2200)
External walls, windows and doors1,976,000278.3120.05%
OMIT aluminium stick and panel curtain walling system; sealed double glazed units; to all elevations 2600 m2 @ (£335)
OMIT aluminium rainscreen cladding; blockwork backing; to roof level enclosed plant rooms and escape stairs 700 m2 @ (£250)
OMIT solar shading; south elevation only 790 m2 @ (£525)
OMIT internal atrium glazing from base scheme 545 m2 @ (£300)
ADD cavity wall construction to two-storey scheme; outer leaf of facing bricks; inner leaf of 140 mm dense concrete blockwork; zero ODP insulation; wind posts. Including allowance for high proportion of additional labours. 1685 m2 @ £300
Reduced solar heat gain from solid wall; embodied energy and toxicity from use of masonry materials. Brickwork and blockwork are A-rated materials in the Green Guide to Specification. Use of locally sourced materials also reduce embodied energy associated with transportation.
Extra over for lime mortar 1685 m2 @ £4   
Facilitates recycling of brickwork at end of building life   
Extra over for sheep’s wool insulation to meet best practice U-value; U-value = 0.25W/m2 C. 1685 m2 @ £9.50
Renewable materials source   
ADD high performance aluminium stick system curtain walling to external wall and lightwell elevations 1560 m2 @ £350
Rate reflects high performance specification with U-value of 0.25 W/m2K and airtightness rating of <7m2/hr/m2
Extra over curtain walling for manually openable windows 60 @ £320  
Provision of responsive workspace through user control of daytime ventilation
Extra over curtain walling for top hung windows; for nightime cooling; electrically actuated; refer to special installations for controls. 56 @ £650
Reduced carbon emissions, running costs and plant replacement costs resulting from nightime cooling and simplification of mechanical installation
ADD tilt-before-turn inward opening framed vents with insulated panels; electrically actuated; refer to special installations for controls. 525 m2 @ £500
Reduced carbon emissions, running costs and plant replacement costs resulting from simplification of mechanical installation
ADD external solar shading to curtain walling; externally mounted, proprietary aluminium louvres 810 m2 @ £250
Enhanced management of solar heat load and glare   
ADD overhanging roof canopy to south elevation. 510 m2 @ £400 
Enhanced management of solar heat load and glare   
Internal partitions131,50018.521.33
Internal doors64,5009.080.65%
OMIT reduced number of lift lobby doors in two-storey scheme. 6 @ (£2000)
Ditto for reduction in riser doors. 8 @ (£1250)   
Wall finishes120,40016.961.22%
ADD lightweight plaster to inside face of masonry walls; emulsion paint. 1685 m2 @ £15
OMIT plaster and paint finishes to concrete core. 1180 m2 @ (15)
OMIT paint finish to concrete columns. 150 m2 @ (£30)   
Cost effect of VOC-free water-borne paints 1685 m2 @ 0   
Minimisation of the use of potentially toxic products   
Floor finishes357,70050.383.63
OMIT adaptation of raised floor for underfloor displacement ventilation; sealing of raised floor plenum; cutting holes for diffusers; bridging over ductwork. 6000 m2 @ (£25)
Ceiling finishes230,50032.462.34%
OMIT mineral fibre suspended ceiling to office areas. 6000 m2 @ (£18)
OMIT allowance for plasterboard margin to office and atrium perimeter. 6000 m2 @ (£11)
ADD self finished acoustic plaster to soffits of upper floors and sloping roof deck of northlights. 7100 m2 @ £25
Furniture and fittings147,50020.771.50%
Sanitary appliances59,5008.380.60%
ADD waterless urinals. Item @ 3,500   
Additional costs of waterless urinals mostly offset by savings in simplified plumbing installation
ADD spray taps and dual flush WCs. 7100 m2 @ £0.50   
Reduction in water consumption by 50% if all three measures are implemented.
ADD PIR control to taps. 7100 m2 @ £1.50   
Water and disposal installations174,40024.561.77%
Extra over for PVC-free materials in water and disposal distribution. 7100 m2 @ £1
Minimisation of the use of potentially toxic products   
ADD additional cost of water and waste distribution pipework to more dispersed toilet provision. 7100 m2 @ £3
ADD solar thermal water heating installation for pre-heat of hot water in toilet cores. 25 m2 @ £1500
CO2 saving of 10 tonnes pa; 25-year payback   
Heat source, space heating and ventilation414,80058.424.21
OMIT reduced capacity of boiler installation (250kW); ultra low NOX 25ppm condenser boilers. 250 kW @ (£40)
Saving related to omission of AHU heater battery   
OMIT mechanical displacement ventilation system including AHUs, chiller, pipework and ductwork distribution. 7100 m2 @ (£60)
Plant rooms and riser provision retained to allow for future retrofit  
ADD extract fans; to ventilation shafts; power wiring and controls. 42 @ £675
Fan-assisted natural ventilation provided to supplement natural cross ventilation
ADD increased length of LTHW perimeter heating installation. 6000 m2 @ £2
Electrical installation646,00090.996.55%
OMIT electrical services cabling and containment to mechanical ventilation and cooling plant.
7100 m2 @ (£2)   
ADD PVC-free materials in electric wiring and conduit; LSF sheathing to cable. 7100 m2 @ £1
Minimisation of the use of potentially toxic products   
ADD additional power supplies to actuator controlled facade and roof openings. 6000 m2 @ £6
OMIT basic recessed lighting installation to suspended ceiling (1 fitting per 4.5 m2).
6000 m2 @ (£32.50)   
ADD exposed up/downlighter lighting installation (one fitting per 4 m2) excluding any attached acoustic treatment. 6000 m2 @ £45
Extra for slimline lighting control boxes located in floor void and allowance for exposed containment systems. 6000 m2 @ £5
Gas installation17,9002.520.18
Lift installations40,0005.630.41
OMIT two passenger lifts serving six storeys. 2 @ (£73,000)  
ADD one passenger lifts serving two storeys. 1 @ £40,000  
Protective installationnilnilnil
OMIT dry riser serving six storeys. Item @ (£12,600)   
Communication installations107,80015.181.09
Special installations184,20025.941.87
OMIT BMS controls associated with mechanical ventilation and cooling system. 50pts @ (£650)
ADD BMS controlled ventilation path and increased control to roof/vent openings to facilitate night-time cooling. 6000 m2 @ £15
Builder’s work in connection68,0009.580.69
External works and services744,600104.877.55
ADD higher proportion of soft landscaping and tree planting to external works areas and internal courtyards. 9050 m2 @ £8
Additional planting to enhance biodiversity   
Preliminaries and contingencies1,475,000207.7514.97
Contractor’s overheads, site establishment and site supervision; including waste management; pollution control and protection of water courses. Allow 12%. Item @ £1,006,000
Preliminaries provision includes recycling of waste, controls on materials disposal, rainwater and grey water recycling; vehicle sharing etc. There is typically no financial effect on competitively tendered projects with a value in excess of £10m
Allowance for waste segregation and recycling schemes. Item @ no extra cost
Recycling can produce cost savings on projects where volumes are large enough and where minimisation of active waste disposal is achieved
Contingency sum. Allow 5%. Item @ £469,000
Construction cost including current best-practice sustainability9,855,8001,388.12100
Additional costs of current best-practice sustainability951,800134.0410.69
Additional costs of enhanced sustainability options
 unit unit rate £overall rate * £/m2 gfa
Extra over steel frame for glue-laminated timber frame m26071
Extra over to upgrade exposed soffit to bespoke precast coffered slabs cast from special mouldsm2150176
Extra over mill finish aluminium for terne coated stainless steelm23022
Extra over for green / landscaped roof of planted sedum (Erisco Bauder or similar)m24030
Upgrade external wall insulation U-values from 0.25 to 0.2 with natural sheep’s wool to achieve leading-edge performancem22.50.70
Building services   
Rainwater harvesting system; below ground storage tank; water treatment; pipework; distribution; builders work m23225
Grey water recovery system. Small packaged units serving shower or changing rooms nr75002.60
Displacement based mixed-mode ventilation system to provide minimum occupancy fresh air; including heat recovery m22531
Dimming facility added to basic category A fit-out lighting control system; dimming cards, universal sensors, dimming ballastm21011
Closed loop heat rejection/collection borehole system. External borehole grid with pipework loops grouted in, connected to header and heat pump installation (approx 120 kW load)nr8500015
Photovoltaics installed on south-facing roof area including AC conversion and cabling m26506
CHP installation to accommodate part load only (250 kVA)kVA100043
Use of pre-loomed structured IT cabling to avoid waste on site generated by cutting cables negligible cost 
External works   
Use of natural organic composts and other soil amelorants negligible cost 
Sustainable urban drainage installations comprising soakaways, permeable pavings and underground attenuation tanks (assumes pavings at 82% of GFA)m23534
Location factors
The cost breakdown is based on a price levels current in the South-east and should be adjusted by the following location factors for schemes in other regions.
Inner London1.13
Outer London1.06
East Midlands0.91
West Midlands0.91
East Anglia0.95
Yorkshire & Humberside0.88
Northern Ireland0.72