Project Cost Calculator
An indicative budget range for building work in London. It covers the construction cost, professional fees, statutory costs, contingency and VAT, because the build cost on its own is rarely the full picture.
Estimated total budget
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Indicative only, based on LACD's rate bands for London. Excludes furniture and loose equipment, AV, utility connections, land and abnormal ground conditions. A fixed price needs drawings and a site visit.
Typical construction rates in London
Construction cost only, before fees, statutory costs, contingency and VAT. Ranges run from Standard to High specification.
| Project type | £ per m² | Typical programme |
|---|---|---|
| Extensions | ||
| Single-storey rear extension | £3,360 – £6,600 | 10–20 weeks |
| Side-return extension | £2,880 – £6,000 | 12–22 weeks |
| Wrap-around extension | £3,600 – £6,240 | 16–28 weeks |
| Double-storey extension | £3,000 – £6,600 | 18–32 weeks |
| Loft conversions | ||
| Loft: Velux | £960 – £2,400 | 4–8 weeks |
| Loft: rear dormer | £1,560 – £3,600 | 8–16 weeks |
| Loft: hip-to-gable | £1,800 – £3,840 | 10–18 weeks |
| Loft: mansard | £2,160 – £4,320 | 10–20 weeks |
| Loft: L-shaped dormer | £1,920 – £4,200 | 10–20 weeks |
| Basements | ||
| Basement: under existing house (underpinned) | £2,400 – £4,420 | 20–40 weeks |
| Basement: lower-ground extension | £1,800 – £3,000 | 16–30 weeks |
| Basement: existing cellar conversion (no major excavation) | £1,200 – £2,640 | 10–22 weeks |
| Basement: under garden / lightwell extension | £1,800 – £3,000 | 16–34 weeks |
| Refurbishment & new build | ||
| Full refurbishment | £960 – £4,200 | 12–36 weeks |
| Flat refurbishment | £1,200 – £4,200 | 8–28 weeks |
| Garage conversion | £750 – £1,500 | 3–8 weeks |
| New-build house | £1,680 – £3,600 | 36–68 weeks |
| Offices | ||
| Office fit-out: CAT A | £450 – £1,030 | 6–18 weeks |
| Office fit-out: CAT A+ | £1,230 – £1,810 | 8–20 weeks |
| Office fit-out: CAT B | £970 – £3,230 | 8–24 weeks |
| Office refurbishment | £580 – £2,130 | 4–20 weeks |
| Office dilapidations / reinstatement | £190 – £1,230 | 3–16 weeks |
| Retail & hospitality | ||
| Retail / shop fit-out | £780 – £2,260 | 4–20 weeks |
| Restaurant / hospitality fit-out | £2,840 – £5,430 | 10–32 weeks |
| Hotel guest-room refurbishment | £1,810 – £4,910 | 6–26 weeks |
| Hotel public-area fit-out | £2,840 – £9,040 | 8–32 weeks |
| Aparthotel / serviced accommodation conversion | £4,520 – £7,100 | 16–44 weeks |
| Per project | ||
| Kitchen | £7,440 – £60,000 per project | 2–8 weeks |
| Bathroom | £9,600 – £30,000 per project | 2–6 weeks |
What else goes into the budget
- Professional fees (architect and structural engineer): 12–17% of the construction cost.
- Contingency: 12–18%. Existing buildings almost always reveal something once opened up.
- Planning application: £660–£780 where needed.
- Building control: £900–£2,640, depending on borough and project size.
- Party wall surveyors: £1,080–£2,160 per neighbour; basements can be higher.
- VAT at 20% on most work. New-build dwellings are zero-rated. Some conversions and long-empty homes qualify for 5%; we confirm this per project.