Cost calculator · 2026
Garage conversion cost calculator London 2026.
Instant indicative cost ranges for every garage conversion type in London. Integral, single, double and tandem garages. Get a personalised range with your postcode and project details below.
Cost table
2026 London garage conversion costs by type.
| Type | Cost range | Timeline |
|---|---|---|
| Single garage to room | £18,000–£35,000 | 4–6 wks |
| Single garage with ensuite | £28,000–£50,000 | 6–8 wks |
| Double garage full conversion | £38,000–£70,000 | 8–12 wks |
| Tandem garage conversion | £25,000–£48,000 | 6–9 wks |
| Integral garage with structural alteration | £35,000–£65,000 | 8–12 wks |
Personalised estimate
FAQ
Garage conversion costs explained.
Do I need planning permission for a garage conversion in London?+
Most garage conversions fall under permitted development (PD) rights — no planning application is needed. However, detached garages that are not integral to the house and any conversion that alters the external appearance significantly may require full planning. Properties in conservation areas or listed buildings always need consent. Integral garage conversions are almost always PD, but you should check with your local borough first.
Is building regulations approval required for a garage conversion?+
Yes — building regulations approval is mandatory for all garage conversions in England, including those under permitted development. The work must meet standards for structural integrity, insulation (walls, floor, roof), damp proofing, ventilation, fire safety, and electrics. Builderr handles the full building control submission and sign-off as part of every contract.
What factors affect garage conversion costs?+
The main cost drivers are: insulation specification (floor, wall and roof — typically 100mm+ rigid insulation), damp proof membrane installation, structural opening creation if joining to the main house, heating extension (wet underfloor or radiator), window and door upgrades, electrical installation, and finish spec. Integral garages typically cost more than detached because the structural alteration to create a through-connection adds steelwork.
How much does it cost to add an ensuite to a garage conversion?+
Adding an ensuite to a garage conversion typically costs £8,000–£15,000 on top of the base conversion cost. This includes tanking (wet area waterproofing), drainage connection, soil stack extension if required, tiling, sanitaryware, underfloor heating, and brassware. A compact shower room (3–4m²) with good-quality fittings sits at the lower end; a larger ensuite with bath adds £3,000–£6,000 more.
How long does a garage conversion take?+
A straightforward single garage conversion to a habitable room takes 4–6 weeks on site. Adding an ensuite extends this to 6–8 weeks. Double garage conversions and integral garages requiring structural alteration run 8–12 weeks. Building regulations inspection and sign-off adds 2–4 weeks after site completion. Total project duration from contract to completion certificate is typically 10–16 weeks.