Rules of thumb - space and weight allowances | Archive Titles

Table 1: Floor space allowance for services (as a percentage of floor area)
Design area	Application	Other information	Rule of thumb
All services	Simple factory		4%
	Offices and commercial		6-10%
	Hi-tech building		15-30%
Air conditioning (excluding boilers and refrigeration)	Fan coil system		1·5-2·5%
	VAV system		3-4·5%
Cooling towers and air-cooled condensers			0.3-1·5%
Electrical services (excluding sub-stations and standby generation sets)			0·5-1·5%
Lift motor rooms			0·2-0·5%
Refrigeration (excluding cooling towers)	Central plant		1-2%
Ventilation	Toilet extract		0.3-1·0%
	Supply and extract systems		3-5%
	All air low velocity system		4-6%

Table 2: Space allowances for service ducts and shafts
Design area	Application	Other information	Rule of thumb
Air ducting		Typical ducting size	0·2 m²/m³/s
Lift shafts	Between 4-18 floors in office type buildings	Internal shaft area
		A: floor area/storey (250 m² min)
		N: floors	3 + A(n-4)/250 m²
Mechanical service riser	Simple pipework riser	Depth needed to open access door/size panel when width of door varies with /type of pipe or depth of service/duct
			690 mm
Pipework		Pipe: 20 mm diamter	100 mm x 100 mm
		Pipe 25 mm diameter	120 mm x 120 mm
		Pipe: 32 mm diameter	130 mm x 130 mm
	Three-sided riser	Minimum depth from service to (open) acess door/panel	690 mm
Service ducts	Vertical service duct	Floor space served by vertical service (radius)	15-23 m
		Aspect ratio of vertical service duct	2:1 to 4:1
		Total duct areas as a percentage of gross floor area	2%

Table 3: Space allowances for plant rooms (floor area)
Design area	Application	Other information	Rule of thumb
Air-cooled condensers and controls		Space for installation and maintenance	25 + kW/200 m²
Air handling units		With extract/recirculation	8 m² per m³/s
		Without extract/recirculation	5 m² per m³/s
Boilers (percentage floor area)	Boiler plant and calorifiers		0·8-1·8%
		Oil tank room	1-2%
Boilers (floor area and height)	Boilers, pumps, piping and space for installation and maintenance	Output 100kW	15 m² x 3 m
		Output: 200 kW	25 m² x 3 m
		Output: 1000 kW	80 m² x 4 m
		Output: 4000 kW	140 m² x 5 m
Calorifiers (floor area and height)	Calorifiers, pumps, pipework, installation and maintenance controls and space for	Vertical: (1 m3)	10 m² x 3 m
		Vertical (5 m3)	20 m² x 4 m
		Vertical (10 m3)	25 m² x 5 m
		Vertical (15 m3)	60 m² x 3 m
		Horizontal (1 m3)	25 m² x 3 m
		Horizontal (5 m3)	30 m² x 3 m
		Horixontal (10 m3)	45 m² x 3 m
		Horizontal (15 m3)	60 m² x 3 m
Chillers (water cooled)	With pumps, pressurisation, pipework and control panels	Output: 1000 kW	50 m² x 3 m
		Output: 2000 kW	63 m² x 3 m
		Output: 3000 kW	83 m² x 3·5 m
		Output: 4000 kW	108 m² x 4 m
Chillers (air-cooled)	Located outside, includes space for installation and maintenance	Output: 200 kW	39 m²
		Output: 400 kW	53 m²
		Output: 600 kW	75 m²
		Output: 800 kW	84 m²
		Output 1000 kW	98 m²
		Output: 1200 kW	116 m²
Cold water storage	Single cold water tank. Includes space for installation and maintenance but add space for pressurisation plant or circulation pumps	FA: floor area
		V: gross storage m²
		1 m high	FA: 10 + V/0·75 m²
		2 m high	FA: 10 + V/1·6 m²
		3 m high	FA: 10 + V/2.4 m²
Cold water storage	Minimum storage for hot and cold outlets	Office – with canteen	45 litres/person
		Office – no canteen	40 litres/person
		Hotel	135 litres/bed space
		Hostel	90 litres/bed space
		Restaurant	7 litres/meal
		Day school	15-20 litres/pupil
		Boarding school	90 litres/pupil
		Children’s home or residential nursery	135 litres/bed space
		Nurses’ home	120 litres/bed space
		Nursing or convalescent home	135 litres/bed space
Hot water storage	Minimum storage capacity	Dwellings	115 litres/bedroom
		Students and nurses’ homes	20 litres/bed space
		Children’s home, elderly sheltered and elderly care home	25 litres/bed space
		Hostels, budget	35 litres/bedroom
		Hotels, 4/5 star	45 litres/bedroom
		Offices, shops and factories	5 litres/person
		Schools: nursery, primary, secondary	5 litres/person
		Schools, boarding	25 litres/person
		Hospitals: district general, surgical ward and medical ward	50 litres/bed
		Hospitals: paediatric	70 litres/bed
		Hospitals: geriatric	40 litres/bed
		Sports changing: sports hall and swimming pool	20 litres/person
		Sports changing: field and all-weather pitch	35 litres/person
		Places of assembly such as libraries, museums and cinemas (excluding staff)	1 litre/person
Cooling towers		FA: floor area (kW: heat rejection)	FA: 50 + Kw/66 m²
Sub-station	200 kVA transformers		47 m²
	Switchgear	HV switchgear	14 m²
		HV + lv switchgear	27 m²
Standby generation	Standby sets and accessories	FA: floor area	FA: 15 + kVA/30 m²
Uninterruptible power supply	Single module system (add space for batteries)
		FA: floor area	FA: (2+ kW/200) x 2 m²

Table 4: Miscellaneous services
Design area	Application	Other information	Rules of thumb
Control panels and distribution boards	Front panel controls, wall mounted or floor standing	Fixed height range (above finished floor or operating platform level)	1200-1800 mm
LTHW boiler plant (component criteria for leakage containment)	Oil storage tanks, distilate and residual fuel oils	If tank fails, walls and doors treated to contain spillage	Tank contents + 10%

Table 5: Space allowances for on-floor services (depth of clear space in ceiling/floor void)
Design area	Application	Other information	Rule of thumb
Air conditioning	VAV		350-750 mm
	VRV		450 mm
	Recessed chilled beams		350-450 mm
	Surface chilled beams		250 mm
	Chilled ceilings		250 mm
	Fan coils		450 mm
	Ducted air systems		450 mm
Drainage		100 mm diameter	10-25 mm per m run
	Solid waste	150 mm diamtere	7-16 mm per m run
Lighting	Fluorescent		100-150 mm (+access)
	Downlighter		150-300 mm
Power and communications	Multi-core cables and lighting cables		100-200 mm
	Power and data (heavy line)		200-250 mm
	Computer rooms		300 mm

Table 6: Space allowances for catering facilities
Design area	Application	Other information	Rule of thumb
Kitchen and dining facilities	Kitchens including preparation and storage	Minimum needs:
		Up to 100 meals	0·4 m²/meal
		Up to 500 meals	0·25 m²/meal
	For single sittings	Ratio of kitchen space to dining space	0·33:1 to 0·5:1
	For multiple sittings	Ratio of kitchen space to dining space	1:1

Table 7: Floor allowance per occupant (net internal area)
Design area	Application	Other information	Rule of thumb
General offices			12-17 m²/person
Trading desks, call centres, workstations			4-6 m²/person
Enclosed offices			15 m² (or more) per person

Table 8: Plant weight allowances
Design area	Application	Other information	Rule of thumb
Single boiler	500 kW		1500 kg
	1500 kW		4250 kg
	2500 kW		6500 kg
Single storage steel calorifier	4 m³		1250 kg
	8 m³		2500 kg
	12 m³		3300 kg
Single non-storage mild steel heating calorifier	500 kW		150 kg
	1000 kW		225 kg
	1500 kW		275 kg
	2000 kW		325 kg
Single water cooled liquid chiller	1500 kW		10 000 kg
	3000 kW		20 000 kg
	4500 kW		30 000 kg
Single air-cooled liquid chiller	500 kW		6000 kg
	1000 kW		11 000 kg
	1500 kW		14 000 kg
Single generator	500 kVA		5000 kg
	1000 kVA		8000 kg
	1500 kVA		11 0000 kg
Single ups system	100 kVA		1250 kg
	300 kVA		2750 kg
	500 kVA		4250 kg