Cost calculator · 2026
London loft conversion cost calculator 2026.
Instant indicative cost ranges for every loft conversion type in London. Based on 200+ completed builds. Get a personalised range with your postcode and project size below.
Cost table
2026 London loft conversion costs by type.
| Type | Cost range | Timeline |
|---|---|---|
| Velux / rooflight | £30,000–£55,000 | 6–8 wks |
| Dormer (rear) | £55,000–£95,000 | 8–12 wks |
| L-shaped dormer | £70,000–£115,000 | 10–14 wks |
| Hip-to-gable + dormer | £75,000–£130,000 | 10–14 wks |
| Mansard | £85,000–£160,000 | 12–16 wks |
Personalised estimate
FAQ
Loft conversion costs explained.
What is the cheapest type of loft conversion in London?+
Velux/rooflight conversions are cheapest, typically £30,000–£55,000, because they avoid structural roof alteration.
What does loft conversion cost include?+
Structural steels, floor joists, stairs, roof works, insulation, plasterboard, electrics, plumbing, heating, decoration, plus design, structural and building control fees.
Is planning permission expensive?+
Planning applications are typically £258 for householder applications in London, plus design fees of £1,500–£4,500.