How much does a single storey extension cost?
Most publishers converge on £1,800 to £3,300 per square metre for a standard to good quality single storey rear extension, before VAT and professional fees. A 30 to 45 square metre extension typically lands between £57,000 and £135,000 depending on region and finish.
£1,800–£3,300 per square metre before VAT and fees
The published figures
Every figure below is a published guide figure, shown as its publisher printed it and linked to the source. Retrieved on 2026-07-17.
| What | Published figure | Basis | Source |
|---|---|---|---|
| Standard quality build | £2,200–£2,500 per m² | excluding VAT | Homebuilding and Renovating (opens in new tab) |
| Excellent quality build | £2,900–£3,300 per m² | excluding VAT | Homebuilding and Renovating (opens in new tab) |
| 30 m² kitchen extension, worked example | £66,000–£99,000 | plus 20% VAT | Homebuilding and Renovating (opens in new tab) |
| Rest of UK | £1,650–£2,600 per m² | Resi cost guide (opens in new tab) | |
| London and the South East | £1,900–£3,000 per m² | Resi cost guide (opens in new tab) | |
| Average single storey extension | £1,800–£3,000 per m² | Federation of Master Builders guide (opens in new tab) | |
| Average terraced house rear extension, total | £30,000–£42,000 | Checkatrade cost guide (opens in new tab) |
What moves the price
- Quality and finish tier
- Footprint complexity and ceiling height
- Size: smaller extensions cost more per square metre because fixed costs do not scale down
- Site access
- Professional fees the build quote often excludes: architect, structural engineer, surveyor, planning, building control, party wall
- VAT
Get real quotes
Guide figures set expectations; only quotes set your price. Compare local businesses on their public evidence:
Sources
- Homebuilding and Renovating (opens in new tab) (trade press, published 2026-02-19)
- Resi cost guide (opens in new tab) (installer, published 2026-02)
- Federation of Master Builders guide (opens in new tab) (trade body, undated)
- Checkatrade cost guide (opens in new tab) (directory site, published 2026)
Figures retrieved from the named sources above on 2026-07-17. Prices change; always confirm with quotes.
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