Cost guide
How much does a side extension cost?
Published UK ranges for a side and side-return extension.
A side extension typically costs £1,800–£3,000 per m² using the general UK extension rate published by HomeOwners Alliance and Checkatrade, while a side-return extension specifically has been quoted at £25,000–£60,000 total by MyBuilder, reflecting the smaller, more constrained footprint typical of this configuration.
Last updated 17 August 2026
| Range | ||
|---|---|---|
| General rate (side extension) | £1,800–£3,000 | Per m² |
| Side-return extension, total project | £25,000–£60,000 | Total project |
Sources: HomeOwners Alliance (2026 guide), Checkatrade (general rate, updated June 2026), MyBuilder (published December 2025)
Key points
- Available width — a side extension is constrained by the gap between your house and the boundary.
- Access during the build, since side extensions are often built in a narrower space than rear extensions.
- Whether the project also involves reconfiguring the kitchen, which is common with side-return extensions.
These are general published ranges, not a quote. Get an estimate based on your own project.
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