In short: a side-return extension typically costs £2,200–£3,200 per m² outside London (more within it) — often £35,000–£70,000 for the build. A wrap-around (side-return plus rear) runs around £2,400–£3,300 per m² and commonly £60,000–£120,000, a 15–25% premium over a simple rear. Figures exclude VAT, fees and fit-out.
Side-return and wrap-around extensions are popular ways to open up a cramped ground floor, especially on Victorian and period terraces. They cost more per square metre than a straightforward rear extension, and it is worth understanding why before you budget. Here are 2026 UK figures and what drives them.
What they are
A side-return fills in the narrow alley that runs down the side of many older houses, usually to widen a galley kitchen into the full width of the property. A wrap-around combines that side-return with a rear extension in an L-shape, giving a much larger open-plan space. The wrap-around does more, and costs more.
Cost by type and size (2026)
| Type | Cost per m² | Typical build cost |
|---|---|---|
| Side-return (single-storey) | £2,200–£3,200 | £35,000–£70,000 |
| Wrap-around (rear + side) | £2,400–£3,300 | £60,000–£120,000 |
London runs materially higher — often £2,800–£5,500 per m² — because of access and party-wall complexity. As a Hampshire-based firm we price to the South East market rather than London rates.
Why they cost more per square metre
A side-return looks small, but several things push the per-square-metre price above a simple rear extension:
- Narrow access — getting materials in and spoil out down a tight side alley is slow and often hand-balled.
- Structural steel — removing the old external wall to open the space up almost always needs steel beams and careful support.
- Lots of glazing and roof — rooflights, bifolds and a new roof over a small floor area mean high fixed costs spread thinly.
- Party wall work — building along a boundary usually triggers a party wall agreement with the neighbour.
What is included — and what is extra
A build figure covers foundations, the shell, roof, standard glazing and basic plastering. Budget separately for VAT (normally 20%), professional and structural fees (commonly 10–15%), the planning fee if needed (£528 in England from April 2026), a party wall surveyor, and the fit-out — kitchen, flooring and decorating. Upgrades like bifold doors and roof lanterns add up quickly on this kind of project.
Planning and party walls
Many single-storey side-returns fall under permitted development, but wrap-arounds more often need a householder planning application because they combine two extension types. Either way, building tight to a boundary usually means serving a party wall notice on the neighbour — start that early, as it has its own timeline. See party wall agreements for an extension and planning permission for a house extension.
Where the brickwork sits
The bricklaying is labour-only — you or your main contractor buy the bricks, blocks, sand and cement, and we lay them, matching the new brickwork to the existing house. Matching an old terrace well matters here because the extension sits right against the original wall; see matching existing brickwork. Compare with our single-storey and two-storey extension cost guides.
Figures are 2026 UK market guides drawn from published cost data and our own experience; treat them as ballpark. Your real price depends on access, structure, spec and where you are.
Getting a price for your extension
Side-returns and wrap-arounds vary hugely with access and structure, so the brickwork is priced after we have seen the job. If you are planning one in Hampshire, Berkshire or Surrey, see our extension work or send us the details and we will come and look.
Frequently asked questions
How much does a side-return extension cost?
In 2026 a side-return extension typically costs about £2,200 to £3,200 per square metre outside London, and more within it. For a common side-return that often works out around £35,000 to £70,000 for the build, before VAT, professional fees and interior fit-out. Narrow access and structural steelwork are what make it dearer per square metre than a simple rear extension.
How much does a wrap-around extension cost?
A wrap-around extension, which combines a rear and a side-return, typically costs around £2,400 to £3,300 per square metre, and commonly £60,000 to £120,000 for the build depending on size and location. It usually carries a premium of roughly 15 to 25 percent over a simple rear extension because it is larger and more complex.
Why are side-return extensions more expensive per m2?
Because they are narrow and awkward. Access down the side of a house is tight, which slows the work and complicates getting materials in and spoil out. They also usually need structural steelwork to open up the old outside wall, plus a lot of glazing and roofing over a small floor area, so the fixed costs are spread over fewer square metres.
Do you need planning permission for a side-return extension?
Sometimes, but many single-storey side-return and wrap-around extensions fall under permitted development if they stay within the size, height and boundary limits. Wrap-arounds are more likely to need a householder planning application because they combine two extension types. It is worth checking early, and a party wall agreement is often needed too.
What is the difference between a side-return and a wrap-around extension?
A side-return extension fills in the narrow alley down the side of a house, usually to widen a kitchen. A wrap-around extension combines that side-return with a rear extension in an L-shape, giving much more space. A wrap-around costs more because it is bigger and more involved, but it often transforms the ground floor.