Cost guide
How much does a side extension cost?
Published UK ranges for a side and side-return extension.
Our own rates for a side 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 side extension typically costs £1,800-£3,000 per m², 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 | ||
|---|---|---|
| Our rate (all specification tiers) - our confirmed rate, excl. VAT | £1,600-£3,500 | Per m² |
| General market rate (side extension) | £1,800-£3,000 | Per m² |
| Side-return extension, total project (market) | £25,000-£60,000 | 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
- 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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Common questions
How much does a side extension cost? FAQs
Is this a fixed quote for my side 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?
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.
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.
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