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Table 1: Comparison of specification standards for 1960-1970s and 1990s office buildings
 19901960s-1970s
Floor loadings5 kN/m2 + 1 kN/m23 kN/m2
Floor-to-floor heights3.6 - 4.1m2.8 - 3.6 m
Floor-plate size1000-2000m2700-1200m2
Floor-plate width15 - 18m10 - 14m
Table 2: Guide rates
Refurbishment options£/m2 gross floor area
Cosmetic refurbishment270 - 380
Refurbishment of services and internal finishes490 - 700
Extensive refurbishment including alterations to structure and cladding810 - 1050
Table 3: Sensitivity analysis of development yield for three rental incomes
scenario 1scenario 2scenario 3
5100 m2 space at£130/m2£160/m2£195/m2
Anticipated rental income (5100 m2 x rent)£663,000£816,000£995,000
Time to purchase at 7% yield per year (100÷7)14.3 years14.3 years14.3 years
Gross development value (income x years to purchase)£9,481,000£11,669,000£14,229,000
Residual profit/loss (gross development value less total development cost of £11,500,000, see table below)-£2,019,000£169,000£2,729,000
Actual development yield (anticipated income ÷ development costs) 5.77%7.10%8.65%
Table 4: Feasibility appraisal for estimated development costs
£total £
Construction costs  
Demolition150,000 
Refurbishment - 6250 m2 @£815/m25,100,000 
External works50,000 
Planning, building regulations fees, survey work, say 1% of construction cost50,000 
Professional fees @ 12%640,000 
Finance costs @ 9% a year based on 50% of construction period415,0006,405,000
Site/existing building purchase   
5500 m2 building @ £540/m22,970,000 
Acquisition costs and fees @ 2%60,000 
Finance costs @ 9% a year420,0003,450,000
Marketing and letting fees  100,000
Development profit @ 12%  1,095,000
Void period  
Finance costs of 9% a year for six months loss of rent 450,000
Total development cost 11,500,000
Cost breakdown
 Element cost (£)Cost/m2 gfa (£)% of total cost
Demolitions and alterations142 53522.812.69
Note: all stripping out and pulling down includes taking away debris and making good to any remaining surfaces
Stripping out existing radiator heating services and boilers etc 5500 m2 @£1.50
Stripping out water and waste services 5500 m2 @£1
Stripping out electrical services 5500 m2 @£1
Removing floor finishes and hacking off existing screeds 5200 m2 @£7
Hacking off existing wall plaster 1900 m2 @£3
Taking down suspended ceiling 5200 m2 @£1.80
Removing finishes and fittings to toilet areas 140 m2 @£5
Removing finishes to stairwell treads and risers 130 m2 @£2.50
Removing staircase balustrades 150 m @£8
Pulling down block spandrel walls, partition walls and doors 1000 m2 @£4
Pulling down timber and demountable partitions and doors 1200 m2 @£2.50
Removing doors from openings in partitions 50 nr @£10
Removing precast concrete external cladding panels 1700 m2 @£6
Removing galvanised mild steel single-glazed windows 1100 m2 @£3
Removing 300 x 400 mm reinforced concrete upstands 900 m @£12
Removing asphalt roof coverings and screeds 1100 m2 @£6
Taking down four-storey steel escape staircase including breaking out foundations 1 @£1,000
Filling to door opening, one brick thick about 1.5 x 2.1 m through 225 mm reinforced concrete wall  5 @£150
Cutting to enlarge opening through half-brick internal wall; new opening 1100 x 2100 mm; existing opening 800 x 2100 mm; forming jambs square; new precast lintel, drypack to existing lintel 10 @£100
Cutting out defective reinforced concrete; blast-clean reinforcement and repalce with repair mortar in areas not exceeding 2 m2 25 m2 @£30
Include for taking down external signage allow£500
Cutting to form opening 1.485 x 2.1 m through 150 mm reinforced concrete wall including 15 Ronafix modified mortar to jambs and head 2 @£300
Cutting to form openings 1.20 x 1.80 through 150 mm rinforced concrete wall including 15 Ronafix modified mortar to jambs and head 40 @£250
Breaking out to form opening 8 x 6 through 300 mm reinforced concrete floor oever entrance foyer including additional framing steelwork 48 m2 @£100
Filling in existing duct openings 2 x 5 m in 300 mm reinforced floors including new concrete, formwork to soffit, 10 mm reinforcement and scabbling edges of existing floor 10 @£160
Diamond saw cutting new openings 2 x .5 m in 300 mm reinforced concrete floor including 15 Ronafix modified mortar to edges 10 @£670
Breaking out to form four openings 5 x 2.5 m through 300 mm reinforced concrete floor slab for new staircase 50 m2 @£70
Substructure12 2001.950.23
150 mm reinforced concrete ground slab and thinkcening to extended slab dowelled in along one edge 130 m2 @£80
200 x 150 mm deep reinforced concrete upstand kerb 180 m2 @£10
Frame142 70022.832.69
Structural steel cantilever extension 700 mm long, one end bolted to frame and perimeter edge beam (1200 m @ 70 kg/m); measure per m2 extended floor area 625 m2 @£160
Structural steel strengthening to one bay for new plant room over 2 t @£1,500
Structural steel frame to lightweight plant room enclosure at roof level including plant support steelwork 4 t @£1,000
Bracing to new stairshaft 4 t @£1,300
Trimming to new riser openings 2 t @£1,500
Fireboard protection to structural steel generally 1100 m2 @£25
Upper floors57 5009.21.08
200 mm reinforced concrete extensio nto upper floor slabs including formwork, reinforcement and dowelling to existing structure 500 m2 @ £80.00200 x 300 mm reinforced cocrete perimeter upstands including formwork and reinforcement  700 m @£25
Roof61 5009.841.16
150 mm reinforced concrete slab to extended roof area including formwork and reinforcement  125 m2 @£48
Warm deck insulation, screed and 19 mm asphalt roofing on felt including work to parapets etc 1200 m2 @£30
Lightweight coated steel cladding to plant room 125 m2 @£60
Perimeter edge and gutter detail to plant room roof 40 m @£25
Galvanised balustrading to roof perimeter 100 m @£110
Stairs29 3004.690.55
Precast concrete dogleg staircase; 3.35m rise 4 flghts @£3,000
Chromium-plated balustrades to main staircase 10 m @£300
Chromium-plated handrails to main staircase 80 m @£100
Painted mild steel balustrade to escape stairs 20 m @£90
Colour-coated mild steel handrail to escape stairs 180 m @£25
External walls1 147 000183.5221.63
Polyester powder-coated aluminium curtain walling system with double-glazed low-emissivity glass and insulated coated aluminium spandrel panels 2900 m2 @£350
Colour-coated aluminium over-cladding, Luxalon or equivalent, on metal grid fixed to concrete and walls  280 m2 @£250
Proprietary independent dry lining as back-up wall to spandrel panels 2800 m2 @£20
Lightweight colour-coated steel wall cladding, Luxalon or equivalent to new plant room 100 m2 @£60
Windows and external doors91 70014.671.73
Polyester powder-coated aluminium double-glazed modular windows 90 m2 @£320
Polyester powder-coated aluminium double-glazed modular fire escape door 1.5 x 2.1 m including frames and furniture 2 @£1,500
Feature entrance screen, doors and canopy in structural glazing 75 m2 @£500
Aluminium louvres to roof plant room 40 m2 @£560
Internal walls38 0006.080.72
Note: Additional partitioning to tenants' floor areas excluded    
Shaft wall system to form new service risers 220 m2 @£30
150mm blockwork in partitions to new staircase tower and cores 210 m2 @£15
100mm blockwork as compartment walls generally 280 m2 @£10
One-hour fire-resisting 70mm Gyproc metal stud partition 3-3.3 m high with 12.5 mm fireboard each side  120 m2 @£35
WC cubicles including doors 35 @£350
WC backwall duct sets; 2200mm high; IPS or similar 90 m @£100
Internal doors50 3508.060.95
Veneered flush doors 10 @£300
Laminate-faced solid flush single doors to toilet etc 25 @£550
Laminate-faced solid half-hour fire-resisting double doors with vision panels to stairwells and lobbies 15 @£1,250
Laminate-faced solid one-hour fire-resisting double doors with vision panels to stairwells and lobbies 11 @£1,350
Wall finishes72 86011.661.37
Two layers 12.5mm wallboard and skim coat to existing concrete columns 480 m2 @£12
13mm plaster and paint to walls 2400 m2 @£7.50
Tassoglass paper to walls and columns 5700 m2 @£7
Ceramic wall tiling on plaster to toilet walls etc 230 m2 @£40
Floor finishes365 40058.466.89
150mm raised-access floor to office areas including carpet tiles 5100 m2 @£50
Cavity barriers  800 m2£10
Carpet on concrete make-up to common areas 400 m2 @£25
Lightweight concrete make-up to lobby areas 900 m2 @£25
Vinyl sheeting to treads and rises of staircases including screeds, nosings and skirtings 190 m2 @£50
Ceramic non-slip tiles on screed to WCs, cleaners' cupboards, kitchenettes 235 m2 @£60
Granite feature flooring to entrance foyer on screed 50 m2 @£140
Entrance mat and frame Item @£1,000
Hardwood skirtings to common and office areas 1600 m @£8
Dustproof sealer to raised floor plenum 5100 m2 @£5
Ceiling finishes46 9607.510.89
Plasterboard dry lining to underside of suspended slabs 4300 m2 @£7
(Trox chilled ceiling panelled system, 5100 m2, included in heat source space heating and ventilation)   
M/F suspended ceiling to common areas 570 m2 @£18
Feature suspended ceiling to entrance foyer 48 m2 @£100
Emulsion paint to soffits of stairs and landings 360 m2 @£5
Fittings and furnishings35 000 5.60.66
Allow sum for kitchenette etc  £5,000
Internal vertical louvre blinds 1000 m2 @£30
Sanitary installation20 0003.20.38
35 white glazed WCs; 5 disabled WCs and fittings; 15 urinals; 35 wash hand-basins in purpose-made vanitory units; 5 cleaners' sinks and 5 stainless steel sinks   
Disposal installation30 0004.80.57
Rainwater, waste and soil disposal in PVCu   
Water installation41 0006.560.77
Mains supply, hot and cold water in copper   
Heating and ventilation1 112 150177.9420.97
Displacement ventilation to office areas 5150 m2 @£28
Chilled ceiling installation to office areas including suspended ceiling complete 5150 m2 @£160
Perimeter heating to office areas 5150 m2 @£22
Pressurisation to cores and staircases 590 m2 @£40
Extract ventilation to toilets and kitchenettes 235 m2 @£30
Electrical installations498 50079.769.4
Complete installtion, including recessed light fittings in chilled ceilings; no standby generation 100 m2 @£85
Common areas and plant rooms 1000 m2 @£65
Lift and conveyor installation50 00080.94
Overhaul of 2 eight-person passenger lifts serving five floors including respraying doors  2 @£20 000
Internal refurbishment of lift cars 2 @£5,000
Protective installations62 500101.18
Addressable fire alarm and security system 6250 m2 @£10
Communication installations129 25020.682.44
Centralised building management system for zoned displacement ventilation system 6250 m2 @£15
Data and telephone wiring provision in dado trunking 5100 m @£5
Public address installation; clocks Item @£10 000
Builders' work in connection146 00023.362.75
Associated builders' work in connection with services allow 7.5%  
Example spot items (provisional quantities)   
Concrete filling to hole 100 x 100 mm in 150 mm reinforced concrete allow 10 @£25
Concrete filling to hole 1000 x 600 mm in 150 mm reinforced concrete allow 3 @£50
Scabbling surface of existing concrete allow 250 m2 @£2
Reinforced concrete in machine bases and plinths including reinforcement and formwork 5 m3 @£200
Cutting chases for conduit 25 x 25 mm; in concrete allow 100 m @£7.50
Cutting chases for conduit 25 x 25 mm; in brickwork/blockwork allow 100 m @£2
Diamond saw cutting rebates in reinforced concrete 25 mm wide x 100 mm deep allow 40 m @£60
Diamond saw cutting holes not exceeding 55 mm diameter in slabs 100-200 mm deep allow 20 @£12
Ditto 200-300 mm deep allow 20 @£18
Diamond saw cutting holes 100 mm diameter in slabs 100-200 mm deep allow 20 @£15
Ditto 200-300 mm deep allow 20 @£20
Diamond saw cutting holes 200 mm diameter in slabs 100-200 mm deep allow 20 @£25
Ditto 200-300 mm deep  allow 20 @£40
Diamond saw cutting holes 200 mm diameter in brickwork/blockwork 100-150 mm thick 50 @£18
Cutting away and making good for lighting, socket outlet and fittng outlet points allow 100 @£5
Subtotal4 382 405701.1882.64
    
Preliminaries438 29570.138.26
Contractor's management and staff, site accommodation and other preliminary items   
Contingencies and design reserve482 30077.179.1
Total for scheme5 303 000848.48100
(excluding site works)   
    
 Cost/m2 gfa (£)  
Other items   
Demolitions and alterations   
External scaffolding - allow 2800 m2 @ £126.5  
Stripping out existing air-conditioning systems etc - 5200 m2 @ £21.66  
Removing asbestos cladding board as duct casings etc - typical rate £20/m2n/a  
Removing asbestos lagging to pipes; including cleaning pipes - typical rate £40/mn/a  
Removing sprayed asbestos to structural beams; including cleaning steelwork - typical rate £70/m2n/a  
Raking shoring to adjoining building - typical rate £5/m2n/a  
Cleaning of external stone facade - typical rate £8/m2n/a  
Cleaning of stained brickwork - typical rate £5/m2n/a  
Cleaning of curtain walling or windows - typical rate £5/m2n/a  
Repair/refurbishment of curtain walling - typical rate £60/m2n/a  
Funigcidal treatment of stonework - typical rate £5/m2n/a  
Repair and redecoration or external windows - typical rate £20/m2n/a  
Upper floors   
Localised strenghtening of 7.6 x 5.25 m bay with additional fire-protected steel beams bolted with friction anchors to existing concrete frame - 40 m2 @ £650.5  
Stairs   
Foundations to new attached staircase block 4.6 x 2.5 x 17.5 m high, curtain walling to three sides, roof over and with 4 staircase dogleg flights and finishes as other escape staircases, complete - 1 @ £100,00010  
[The construction of the staircase outside the building footprint will increase lettable area by 45 m2 (0.8%)]   
External walls and windows   
Coated steel Luxalon cladding on metal support rails including 140 mm concrete block back-up wall (2000 m2 @ £80) plus polyester-coated aluminium double-glazed windows (1300 m2 @ £350)-90  
Coated steel Luxalon cladding on metal support rails including 140 mm concrete block back-up wall (2000 m2 @ £80) plus polyester-coated aluminium double-glazed windows with interstitial blinds (1300 m2 @ £500)57  
Heat source, space heating and ventilation   
Radiator heating system with localised extract - 5150 m2 @ £60-168  
Fan-coil unit comfort cooling system - 5150 m2 @ £180   
Communications installations   
Central building management services system for fan-coil unit comfort cooling system - 6250 m2 @ £206  
Protective installations   
Single-level sprinklers with heads at 9 m2 - 6250 m2 @ £1012  
Regional Variations
All costs in this model are based on a scheme in Outer London and should be adjusted by the following location factors for schemes in other areas:
Inner London1.08
Outer London1
East Anglia0.85
East Midlands0.83
North0.86
Northern Ireland0.68
North-west0.85
Scotland0.91
South-east0.91
South-west0.84
Wales0.83
West Midlands0.84
Yorkshire and Humberside0.85