Cost guide
How much does a rear extension cost?
Published UK ranges for a single-storey rear extension.
Our own rates for a rear extension run £1,600-£3,500 per m² excluding VAT, depending on specification tier - use the cost calculator for an estimate based on your project. For general UK market context, a rear extension typically costs £1,800-£3,000 per m², putting a typical 20-30m² rear extension in the region of £40,000-£84,000. MyBuilder separately quotes £20,000-£40,000 as a total for a straightforward rear extension project.
Last updated 17 August 2026
| Range | ||
|---|---|---|
| Our rate (all specification tiers) - our confirmed rate, excl. VAT | £1,600-£3,500 | Per m² |
| General market rate | £1,800-£3,000 | Per m² |
| Typical total project (market) | £20,000-£40,000 | Total project |
Sources: HomeOwners Alliance (2026 guide), Checkatrade (general rate, updated June 2026), MyBuilder (published December 2025)
These are general UK ranges. We build across the North West, including Darwen, Blackburn and the wider Lancashire and Greater Manchester area - site access, local trade rates and travel distance can move your actual price within (or occasionally outside) the range above.
Key points
- How far you extend - permitted development depth limits (4m for a detached house, 3m for others, under the standard rules) are often the practical ceiling before a full planning application is needed.
- Whether the extension opens the ground floor into a kitchen-diner, which usually means removing a structural wall.
- Roof design and how much natural light reaches the rest of the ground floor.
These are general published ranges, not a quote. Get an estimate based on your own project.
Start Your ProjectWant a price based on our own rates, not a market average? Take the cost calculator quiz →
Looking at how much does a rear extension cost?? See how we approach it →
Common questions
How much does a rear extension cost? FAQs
Is this a fixed quote for my rear extension?
No. The figures above are published UK industry ranges from HomeOwners Alliance and Checkatrade and MyBuilder, not a quote for your project. An accurate price depends on a site survey and your specific requirements - get in touch for an estimate based on your own project.
What actually drives the price up or down?
How far you extend - permitted development depth limits (4m for a detached house, 3m for others, under the standard rules) are often the practical ceiling before a full planning application is needed. Whether the extension opens the ground floor into a kitchen-diner, which usually means removing a structural wall.
What's a typical our rate (all specification tiers) in per m² terms?
Our rate (all specification tiers) typically runs £1,600-£3,500 (per m²), for a our confirmed rate, excl. VAT, based on the sources cited above.
Other cost guides
More published cost ranges
How much does a loft conversion cost?
Published industry ranges by conversion type, so you can budget sensibly before getting a quote.
How much does a house extension cost?
The published UK per-m² rate for a single-storey extension, and what actually moves it.
How much does a two storey extension cost?
Published per-m² rates by build quality, and what a typical two-storey extension runs in total.
Ready to make more of your home?
Tell us what you're thinking and let's see what's possible.
Start Your ProjectMore Space, Built to Last.