PRICE GUIDE · TRADES & CONSTRUCTION · 2026–2027
House Extension cost in the UK
£1,800–£4,000 per m². Typically £2,700.
A UK house extension costs £1,800–£4,000 per m², with around £2,700 per m² typical for a mid-range build. Specification moves it most — basic finishes versus large glazing, steelwork and underfloor heating — along with one or two storeys, ground conditions and building in London.
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HOW MUCH IT COSTS
How much does house extension cost in the UK?
| Low end | £1,800 | a simple single-storey extension with standard finishes |
|---|---|---|
| Typical | £2,700 | what most people pay |
| High end | £4,000 | a high-spec extension with large glazing, in London |
Locufy guide prices for 2026–2027. Updated 2026. A national range, not a quote — enter your town above for real prices from the builders and trades near you.
What moves the price
- Specification — standard finishes cost far less per square metre than bifold doors, roof lanterns and bespoke details
- One or two storeys — a two-storey extension shares foundations and roof over more floor, cutting the cost per m²
- Kitchen or bathroom inside — fitting a kitchen or bathroom in the extension adds thousands to the build
- Ground conditions — clay, trees or drains under the footprint push up foundation costs
- Structural steel — removing the rear wall to open up the house needs beams and an engineer
- Region — extensions in London and the South East cost noticeably more per square metre
Building and repair prices in the UK are up 6% over five years (ONS Consumer Price Inflation, Services for maintenance and repair, to 2026 August). Five years ago a typical house extension would have cost about £2840 — an estimate from today's guide price and that index, not a recorded price. Source: ONS MM23 D7DO →
WHAT YOU GET
What a house extension booking includes
Takes: Ten to sixteen weeks on site for a single-storey extension, longer for two storeys. Not included: Architect and engineer fees, planning and building control charges, kitchen units and decoration are usually priced separately — see the related guides below.
WHAT PEOPLE BOOK
Common house extension jobs
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House Extension near you, with prices shown
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How to pay less
- Keep the extension a simple rectangle with a standard roof to hold down the cost per square metre
- Finish the extension design and choose fittings before work starts so the builder prices once
- Build two storeys at once if you will need the space, as the cost per m² falls with the second floor
Before you book
- Check the permitted development size limits, and whether your home still has those rights, before designing a single-storey extension
- Every extension needs building regulations approval, covering structure, insulation, drainage and fire safety
- Serve party wall notices if you dig near or build on a shared wall with a neighbour
- Tell your home insurer and lender about the extension before building starts
House Extension cost: questions people ask
£1,800–£4,000 per m², with around £2,700 typical. A simple single-storey extension with standard finishes costs least per metre; a high-spec build in London costs the most.
About ten to sixteen weeks on site for a single-storey extension, after design and approvals, and longer for two storeys.
Not always. Plenty of modest single-storey rear additions count as permitted development, and larger ones can go through the prior approval route. Two-storey extensions, some side extensions and anything in a conservation area often need full permission.
Per square metre, usually yes, because the foundations and roof are shared across two floors of space.
Architect and engineer fees, planning and building control charges, kitchen or bathroom fittings and decoration are generally extra.
They are Locufy guide prices for the UK, drawn up from published UK extension cost guides — a national range, not a quote. Specification and region decide your real cost.