Cost model - Urban Commercial Offices | Archive Titles

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	(%)
	Minimum	Maximum	(£/m² 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.