Cost model: School extensions | Features

Classroom extension cost breakdown
	element cost	cost/m2 gfa £	% of total cost
Substructure	36,100	116.45	9.12
Excavation and disposal 140 m2 @ 30
Concrete strip foundations, masonry work below DPC; blockwork and facing brickwork 90 m @ 130
Reinforced insitu concrete foundations and ground slab, including service trench; vapour barrier; hardcore, excavation and disposal 310 m2 @ 65
Roof	50,200	161.94	12.68
Softwood roof trusses 380 m2 @ 35
Board insulation to roof 310 m2 @ 15
Cement slate roofing including all eaves, ridge tiles and labours; measured on plan 380 m2 @ 60
Aluminium rainwater down pipes 40 m @ 75
Aluminium gutters 90 m @ 65
Fire barriers 40 m @ 15
External walls	30,800	99.35	7.78
Brick cavity wall, facing brick outer skin with cavity, 140mm inner blockwork leaf 220 m2 @ 140
Windows and external doors	29,100	93.87	7.35
Proprietary aluminium framed, double glazed windows, doors and solid aluminium faced panels; powder coated finish 55 m2 @ 350
Double door steel security doors, including all ironmongery 1 @ 1,600
Double door aluminium framed glazed doors and screens to paved areas, including all ironmongery 15 m2 @ 550
Internal walls and partitions	12,200	39.35	3.08
Partitions; 100/140 blockwork (average rate) 285 m2 @ 35
WC cubicle partitions; laminated plastics, including all ironmongery 4 @ 550
Internal doors	9,700	31.29	2.45
Internal fire doors, georgian wired glass vision panel, stainless steel ironmongery to classrooms 5 @ 900
Double fire door, georgian wired glass, stainless steel ironmongery to corridor 1 @ 1,100
Wrot softwood storage cupboard door, stainless steel ironmongery 5 @ 450
Non fire-rated doors, stainless steel ironmongery to WC 3 @ 600
Wall finishes	13,200	42.58	3.33
Plaster and one mist coat, three coats of emulsion paint 760 m2 @ 15
Ceramic wall tiles, full height in toilets and selected classroom areas 40 m2 @ 45
Floor finishes	14,400	46.45	3.64
Screed cement screed 310 m2 @ 15
Carpet tiles 150 m2 @ 25
Safety vinyl to WC areas and practical areas, including skirtings 90 m2 @ 30
Heavy duty vinyl to circulation areas, including skirtings 68 m2 @ 40
Entrance matting with aluminium matwell 2 m2 @ 275
Furniture and fittings	19,500	62.9	4.92
Storage trays containers 3 @ 2,500
Storage units – allowance of one double cupboard per classroom 3 @ 500
Worktops, including cut out for sink, 3000x600 3 @ 125
Coat hooks, fixed to masonry 100 @ 25
Pinboards, 1000 × 2000 6 @ 75
Pinboards, 1000 × 1200 2 @ 50
Whiteboards: Interactive 3 @ 1,500
Whiteboards: Magnetic 3 @ 100
Signage 1 @ 2,000
Mirrors 640 × 460 7 @ 40
Sanitary fittings	5,100	16.45	1.29
WCs 6 @ 210
Urinals, including side panel 2 @ 220
Hand basins 8 @ 180
Disabled toilet, including WC, wash hand basin, grab rails and other fittings 1 @ 700
Single stainless steel sinks to classrooms, 1200 × 600 3 @ 200
Cleaners sink, 510 × 380 1 @ 700
Disposal installations	6,200	20	1.57
Waste, soil and vent installation; PVCu pipework and fittings 310 m2 @ 20
Water installations	9,200	29.68	2.32
Cold water points 21 @ 250
Hot water points 13 @ 300
Space heating and air treatment	37,200	120	9.39
Space heating, all costs associated with the supply and installation of the heating system, temperature control and distribution pipework 310 m2 @ 120
Ventilation installations	5,000	16.13	1.26
Ventilation extraction to WC areas Item @ 5,000
Electrical installations	31,000	100	7.83
Mains and sub-mains installation 310 m2 @ 20
Small power installation 310 m2 @ 30
Lighting and general luminaires; emergency lighting 310 m2 @ 50
Gas installation	1,600	5.16	0.41
Gas Installations, all costs associated with the supply and installation of gas 310 m2 @ 5
Protective installations	1,000	3.23	0.25
Lightning protection, earthing and bonding 1 Item @ 1,000
Communications installation	12,200	39.35	3.08
Fire alarm installation; smoke detectors; call points Item @ 4,000
Telephone and data wireways; internal telephone system Item @ 2,200
Security installation; intruder detection, CCTV to existing control unit etc 1 Item @ 6,000
Builder's work in connection	5,400	17.42	1.36
Forming holes, chases etc, allow 5% Item @ 5,400
Preliminaries and contingencies	60,400	194.84	15.25
Preliminaries, allow 15% Item 50,300
Contingency sum, allow 3 % Item 10,100
Total construction cost – building only	396,000	1,277.41	100

Alternative design options
Extra over cost/saving inclusive of preliminaries and contingencies (£/m2) GIFA
Option 1: Replace a blockwork inner wall with a sliding folding partition, including building in steel beam	30
Option 2: Dedicated ICT suite in small room, cost of benching not included	18.5
Option 3: Replace brick cavity walling with timber rainscreen cladding	37.5
Option 4: Replace brickwork cavity wall with a render finish on blockwork cavity external wall	–10.50
Option 5: Replace pitched cement tiles with Decra metal roof tiles	14
Option 6: Replace pitched cement tile roofing with single ply membrane	–10.00
Option 7: Replace cement tile roofing with a green roof system	–75.00
Option 8: Replace all internal blockwork partitions with acoustic metal stud partitions	5.5
Option 9: Replace 50% of the plaster and paint to blockwork walls with hygienic plastic sheeting	58