Costs
What a house extension costs
Indicative 2026 UK ranges, and the decisions that move the number more than the floor area does.
| Extension type | Typical UK range, built and finished |
|---|---|
| Single-storey extension | £24,900 – £50,200 |
| Side extension | £16,300 – £37,700 |
| Two-storey extension | £50,200 – £90,300 |
Source: BestBuilders’ 2026 regional cost model — published national cost guides adjusted by a regional labour index and averaged across 519 UK towns. Indicative ranges for a typical specification, not quotes. London and the South East sit above them; the North, Wales and Scotland below.
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Get free quotesWritten and checked by the HouseExtensionExpert editorial team · Last updated: 31 August 2026 · Planning and Building Regulations points are checked against current Planning Portal and GOV.UK guidance; cost ranges come from BestBuilders’ 2026 regional cost model (published national cost guides × a regional labour index, averaged across 519 UK towns). Ranges are indicative, not quotes.Next scheduled review: November 2026 · Spotted something out of date? Tell us.