UK Extension Cost Per m² 2026 — From £1,820 in Liverpool to £3,640 in Inner London
The 100% London-vs-rest-of-UK premium on single-storey extensions — 2026 priced
"A homeowner in Liverpool can build the exact same 20m² rear extension for half the price of an inner-London neighbour. Materials cost the same; British labour is what divides them."
— TradeMatch UK Editorial Team
How this study was carried out
TradeMatch sampled 1,140 completed, escrow-released single-storey rear extensions of 15-25m² internal floor area between Q1 2024 and Q1 2026. All projects were Building-Control-signed-off, with planning permission or permitted-development confirmation. Cost is gross labour + materials, exclusive of VAT, exclusive of design / planning / structural-engineer fees.
Sample: 1,140 completed single-storey rear extensions across UK postcodes, 2024-Q1 to 2026-Q1
What this study found
- A 20m² rear extension costs £36,400 in Liverpool and £72,800 in inner London — a £36,400 gap on identical scope
- The £/m² national average is £2,470 in 2026, up from £2,140 in 2023 (+15.4%, ahead of headline CPI)
- Material cost (~£900/m²) is broadly flat across the UK; the regional gap is almost entirely labour
- Extensions over £75,000 typically include premium specification (bifolds, high-spec kitchen, underfloor heating); the like-for-like figures here strip those
TradeMatch completed-extension data, single-storey rear, 15-25m², Q1 2024 to Q1 2026
| City | Cost £/m² (Avg) | 20m² Total Extension | vs Liverpool |
|---|---|---|---|
| Inner London | £3,640 | £72,800 | +100% |
| Outer London | £3,180 | £63,600 | +75% |
| Brighton | £2,940 | £58,800 | +62% |
| Bristol | £2,720 | £54,400 | +49% |
| Cambridge | £2,690 | £53,800 | +48% |
| Edinburgh | £2,580 | £51,600 | +42% |
| Bath | £2,490 | £49,800 | +37% |
| Manchester | £2,310 | £46,200 | +27% |
| Birmingham | £2,180 | £43,600 | +20% |
| Leeds | £2,070 | £41,400 | +14% |
| Glasgow | £1,980 | £39,600 | +9% |
| Liverpool | £1,820 | £36,400 | 0% |
Why this matters
Single-storey rear extensions are one of the most homogenous UK home-improvement categories — the design vocabulary (steel beam, foundations, blockwork, plaster, single-ply roof) is broadly consistent nationally. The £/m² spread captures pure labour and overhead variance plus the local builder mix. London builders carry higher overhead (vans, parking, congestion), but the 100% premium against Liverpool exceeds what overhead alone explains; the rest is wages, demand and the elasticity of the inner-London property-improvement market.
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FAQ
Does this include VAT?
No — all figures are exclusive of VAT. UK builders over £85,000 turnover are VAT-registered (20%); below that, no VAT. Most builders working on extensions of this scope are VAT-registered.
What about design and planning fees?
Excluded. Architect / structural engineer fees typically add £3,000-£8,000 on a 20m² extension; planning fees (if non-permitted-development) add £206 (householder application, Apr 2026 fee).
How long does a 20m² rear extension take?
8-14 weeks of on-site work for a competent UK builder. London projects average 11 weeks; northern projects average 9 weeks (less weather-driven scheduling friction).
Should I use a project manager?
For a 20m² rear extension, a homeowner-project-managed approach saves £1,500-£4,000 of builder margin but typically extends the project by 2-4 weeks. Most homeowners use a head builder who subcontracts the trades — the middle-cost option.
Cite this study
Citation: TradeMatch UK (2026). UK Extension Cost Per m² 2026 — From £1,820 in Liverpool to £3,640 in Inner London. Available at: https://www.tradematch.uk/data/uk-extension-cost-per-m2-2026
Granular data and per-postcode breakdowns are available to UK media outlets on request to [email protected]. Released under CC-BY 4.0 — re-use freely with attribution.
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