Side return extension in London
Fill in the alleyway beside your Victorian or Edwardian terrace and gain 10 to 18 square metres of kitchen, without losing the garden. Designed and built by one team, priced in writing before you commit.
A side return extension with Build Team costs £45,000–£140,000 (October 2026); the table below shows what each price includes. Expect around 12 weeks of design and planning, then 12–14 weeks on site. Most boroughs allow a side return under permitted development, but an Article 4 direction or conservation area means a full application and 4–8 extra weeks. Build Team has completed 1,750+ projects across London since 2007.
What is a side return extension?
A side return extension fills in the narrow alleyway that runs alongside the rear outrigger of a typical Victorian or Edwardian terrace, squaring off the L-shape at the back of the house. It usually adds 10–18 square metres, which is why it is the most common way to turn a narrow “skinny kitchen” into a full-width kitchen-diner.
Because the extension sits within the existing footprint of the plot, you keep your garden. Most side returns take a flat or lean-to roof with rooflights or a glass panel along the length, so the new room is brighter than the original kitchen despite being deeper. In London the format suits terraces in East Dulwich, Clapham, Brixton, Balham, Walthamstow, Leyton, Ealing and most inner boroughs with pre-1920 housing.
How much does a side return extension cost in London? (October 2026)
| Option | From | To | Per m² | Includes |
|---|---|---|---|---|
| Shell only, small (8–10 m²) | £45,000 | £60,000 | £3,500–£4,200 | Structure, foundations, roof, glazing, first-fix electrics and plumbing |
| Shell only, typical (12–15 m²) | £60,000 | £85,000 | £4,200–£5,000 | As above, larger footprint, bi-folds |
| All-in, typical (12–15 m²) | £80,000 | £110,000 | £6,500–£8,000 | Shell plus kitchen fit-out, finishes, VAT, fees, party wall, contingency |
| All-in, large or glass roof (15–18 m²) | £110,000 | £140,000 | £7,000–£8,500 | As above with structural-glass lantern or premium bi-folds |
Prices updated October 2026. All prices include VAT unless stated.
How to design the right layout for your side return extension
Every house is different, but the plan on the left shows the arrangement that works most often for this type of extension: the kitchen against the flank wall, the dining table in the widest part of the new space, and the doors placed so the garden is visible from the hallway.
The measured survey at the start of the Design Phase is what settles it for your house. We draw two or three arrangements and you choose.
How long does it take?
A side return extension takes around six months from the first design meeting to handover. The design phase runs about 12 weeks: two weeks for the measured survey and concept, eight weeks for the council’s planning decision (or a Lawful Development Certificate), and two weeks for Building Regulations drawings and structural calculations. The build itself takes 12–14 weeks on site.
- Weeks 1–2: survey, concept design, your feedback
- Weeks 3–10: planning application or Lawful Development Certificate
- Weeks 11–12: Building Regs pack, structural calcs, party wall notices
- Weeks 13–26: build, with a named Build Manager on site
Things that add time: an Article 4 direction or conservation area (add 4–8 weeks), a party wall dispute (add 2–6 weeks), and structural-glass roofs, which have longer lead times than rooflights.
Will it need planning permission?
A side return extension usually does not need planning permission, as long as it stays within permitted development. The rules are in the Town and Country Planning (General Permitted Development) (England) Order 2015, Schedule 2, Part 1, Class A. A single-storey side extension qualifies if it is no wider than half the width of the original house and no higher than 4 metres. The materials must look similar to the existing house. Most London side returns fit inside those limits. We still recommend a Lawful Development Certificate so you have the council’s confirmation in writing.
A full planning application is needed for a flat, a listed building or a house in a conservation area. The same applies where the council has removed permitted development rights with an Article 4 direction, which is common in parts of Hackney, Camden, Islington, Lambeth and Westminster, or where the design goes beyond the Class A limits. We check which applies to your address before we draw anything, and we handle the application if one is needed.
What can go wrong, and how we handle it
My side return will cost more than the quote.
The build price is fixed in writing before you sign. Only changes you ask for move it, and each one is priced and agreed before the work is done. On a side return the one genuine unknown is the ground under the old alleyway, so the quote carries a contingency for it rather than leaving you to find out later.
The builder will sub-contract and disappear.
Your Build Manager is a Build Team employee who is on site through the whole job, and the same person from the first day to the snagging visit. Trades are our regular teams, not whoever is available that week. Every side return we build carries a 3-year structural guarantee plus 2 years' defects liability, so we come back if something goes wrong.
The neighbours will object and hold everything up.
A side return wall sits on or next to the boundary, so the neighbour on that side gets a party wall notice. We serve it ourselves, with drawings, and can appoint the surveyor. If the neighbour dissents, the Party Wall etc. Act 1996 sets out what happens next, and the work goes ahead under the award.
How Build Team designs and builds your side return extension
Build Team designs your side return for a fixed fee, then builds it on a fixed-price contract. The Design Phase covers the survey, drawings, planning and Building Regulations, and our Ready to Build design fees start from £3,995 for a ground floor extension. At the end of it you can use the full set of drawings with any builder. The Build Phase has a named Build Manager who runs the site day to day and reports to you weekly.
On a side return the critical detail is where the new steel bears on the party wall and the old outrigger wall. Because design and build sit in one company, the person who drew that detail is on hand when the steel goes in. The gap between drawing and building is where most extensions go wrong.
Recent Build Team side return extension projects
Side return extension FAQ
Our current prices for a side return are £45,000–£140,000 (October 2026), depending on the size, the roof and the glazing. The cost table on this page shows each option and what the price includes.
Most side return extensions do not need planning permission. Single-storey side returns fall under permitted development (GPDO 2015, Class A) as long as they are no wider than half the original house and no higher than 4 metres. You will need a full application in a conservation area, under an Article 4 direction, or for a flat or listed building. We check your address before we start.
A side return extension takes about six months in total: roughly 12 weeks of design and planning, then 12–14 weeks on site. Article 4 areas and structural-glass roofs add a few weeks each.
A side return does not take any garden. The extension fills in the alleyway beside the house, within the existing footprint of the plot, so the garden stays the same size. Many designs include a glass roof or wide doors so the kitchen feels connected to it.
Most clients stay at home during a side return build. The work is at the back of the house and we seal the site off from the rest of the home. You will be without a kitchen for part of the build, so we agree a temporary set-up with you before we start.
A side return almost always needs a party wall agreement, because the new wall sits on or next to the boundary with your neighbour. Build Team serves the notice for you under the Party Wall etc. Act 1996, and we can appoint the surveyor too. Allow for one neighbour in the budget; two if you are mid-terrace and both sides are affected.
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