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TABLE 1: Key design criteria for urban offices
Design criteria Specification standard      
BCO BCO DLE survey DLE survey
Specification for
urban offices		 Best practice in the
specification for offices		 (lowest value) (highest value)
Occupational density indoor climate control (person/m2) 1:14 1:14 1:14 1:10
WC provision (gender split/person/m2) 60/60@1:14 60/60@1:14 50/50@1:14 50/50@1:14
Fresh air ventilation (litres/sec/person) 8-12 8-12 12 20
Cooling loads        
Small power (W/m2) 15 15 15 25
Lighting (W/m2) 12 12 12 20
Primary power        
Equipment (W/m2) 25 15-25 15 25
Lighting (W/m2) 15 12 12 20
Lighting        
Office areas (lux) 400-500 350-400 350 500
TABLE 2: COST SUMMARY
Elemental split Range within analysis   Cost model Ìý(%)
Minimum Maximum (£/³¾2 GIFA)  
Public health installation 20 30 25.70 7·2
Mechanical installation 140 205 186.25 51·9
No sprinklers 3 5 4.10 1·1
Sprinklers 17 25 24.75 6·9
Electrical installation 105 135 118.25 32·9
Total 285 400 359.05 100
The wide range of costs is a reflection of the range of standards to which systems have been designed and the variation in quality that can be expected from scheme to scheme. It is also due to variation in the extent of fit-out that is provided as part of the Category A developer’s finish. For example, fan-coil units have been provided in densities ranging from one fan-coil unit per 30 m2 of overall floor area to one per 50 m2 of overall floor area.
Such factors clearly have a substantial effect upon the variability of the initial costs of office developments. Other variables, including market conditions, location, programme, procurement route and contract, also need to be factored into the capital cost equation.
Costs are at 4th quarter 1998 price levels based on a central London location. They include allowances for 2·5% main contractor’s discount, but exclude the costs of the main contractor’s overheads, profit and attendance. Costs also exclude external works and contingencies.