House Extensions Brixton
Single storey rear and double storey extensions in Brixton, planning, structure and build under one contract.
- Rated 4.9 from 31 reviews on MyBuilder
- Single-storey rear extension from £40,000
- Free site survey, itemised quote
GS Renovation builds extensions across Brixton, working with the side returns, rear closet wings and tight urban plots typical of SW2's Victorian and Edwardian terraces. We take your extension from foundations and steelwork through roof and full fit-out, and we tell you clearly whether it is permitted development or needs planning permission.
In Brixton, a single-storey rear extension typically starts from £40,000, or £2,000 to £2,800 per m² (indicative London ranges, Architecture for London, Resi, MyBuilder and Checkatrade, 2026). GS Renovation Ltd, a building contractor based in Potters Bar, does the work in Brixton: the structural engineer we appoint designs the structure, we build it, and building control signs it off.
Price guide
| Work | Indicative London range |
|---|---|
| Single-storey rear extension | from £40,000 |
| Rear extension, per m² | £2,000 to £2,800 |
| Side return, per m² | £2,400 to £3,200 |
| Wraparound, per m² | £2,400 to £3,200 |
| Double storey, per m² | £1,800 to £2,600 |
| Basement extension | see the basement page |
Indicative London ranges (Architecture for London, Resi, MyBuilder and Checkatrade, 2026), not a quotation. Prices checked September 2026. Full breakdown: Extension Costs & Planning.
Quick estimate for Brixton
Brixton range: choose above
Side-return extensions in Brixton
The side return, that narrow strip of yard beside the rear closet wing, is the classic space to claim on a Brixton terrace. Infilling it widens a cramped galley kitchen into a full-width kitchen-diner that runs across the back of the house. We dig new foundations to suit the ground, tie into the existing wall carefully and install a steel beam where we open up the old external wall.
Many side-return and modest rear extensions on SW2 terraces fall under permitted development, but that is never guaranteed. If your home sits in a conservation area, has been extended before or you want a larger footprint, you may need a full planning application to Lambeth Council. We assess your permitted development rights at the outset, coordinate the drawings with your architect or designer and, where required, follow the planning submission through so you know exactly where you stand.
Housing in Brixton
Brixton has around 21,700 homes on the Council Tax list: 44% post-war, 8% interwar and 47% predate 1919, with 80% flats and 20% houses. Most homes here are flats, and a flat in Brixton has no householder permitted development rights, so extending one needs planning permission and the freeholder's consent.
Where the Brixton conservation area statement leaves room to extend
The Brixton Conservation Area Statement says there is often little scope for extensions other than on rear elevations and on some rooftops. For a house inside the area, that points any extension to the back. A side extension to the street, or anything that changes the front of a bay fronted terrace, starts from a position where the statement expects little scope. So the useful design question in Brixton is how much depth the rear can take and how the new work meets the closet wing and the neighbour's boundary, not whether the front can be pushed out.
Timing follows from the route. Only 19% of Brixton homes are terraced houses, and only houses have householder permitted development rights; a flat needs planning permission for any extension. Inside a conservation area a house keeps its right to a single storey rear extension within the usual limits, but a side extension or a rear extension of more than one storey needs an application. Lambeth says a householder application for works to an existing home should get a response in 8 weeks. We confirm whether the property is a house or a flat, and whether it sits in the conservation area, before promising any start date.
Double storey extensions across Brixton
A double storey rear or wrap-around extension adds a bigger kitchen below and a bedroom or bathroom above, a popular way to gain space on Brixton's family terraces without moving away from Brockwell Park and Clapham Common. These schemes usually need a full planning application, deeper foundations and heavier steelwork. We coordinate the engineer, the ground works and the roof so the new floor sits true and the elevations match the existing brick.
Because these terraces share party walls with both neighbours, a double storey build almost always triggers the Party Wall Act, and excavating near the boundary needs formal notices too. You serve those notices as building owner; we supply the drawings, programme the work around them and handle the building regulations approvals alongside, keeping neighbours informed. Once the shell is watertight, the same team fits it out completely, plastering, joinery, kitchen, bathroom, electrics and heating, so you deal with one contractor from the first dig to the last coat of paint.
Kitchen extensions in Brixton
80% of homes in Brixton are flats, and a flat has no householder permitted development, so a ground-floor flat's kitchen extension needs planning permission from Lambeth Council and the freeholder's consent. Most kitchen extensions here are on the 20% of homes that are houses. The fit-out is priced on its own page, kitchen renovation in Brixton; the build figures are in the table above.
- Building control inspections at foundation, damp course and steel stages
- Brickwork and mortar matched to the existing elevation
- Steel goalpost frames where the rear wall opens up
VOA Council Tax stock of properties, March 2025, for all 5 statistical areas in Brixton. Counts rounded by the VOA.
Trusted House Extensions in Brixton
Homeowners across Brixton choose GS Renovation because we manage the whole extension, coordinating the engineer's structural design and building the foundations, steel, roof and fit-out ourselves. We are honest from day one about whether your project is permitted development or needs a Lambeth Council application, we coordinate the work around the party wall award with neighbours, and our founder's 30+ years on the tools means we understand exactly how these terraces are built.
- Insulation and thermal detailing to current regulations
- Weathertight shell reached before the fit-out begins
- Neighbours given notice before the noisy stages
Built a new extension at rear of property. Laid foundations, drainage, raised floor, new roof and completed all fixtures and interior decoration…
George was brilliant. Lovely bloke, very reasonably priced and a perfectionist to boot. He completed our small kitchen renovation with care and great…
George always kept to commitments and arrived on time. He offered helpful suggestions during his initial visit and promptly provided a reasonably…
FAQ
Frequently Asked Questions about House Extensions Brixton
Which parts of a house extensions project in Brixton cost the most?
On a house extensions project in Brixton the approvals are a small line and the time on site the large one, within £2,000 to £2,800 per m² for a rear extension (indicative). The cost of a Lambeth Council building control inspection of the foundations before concrete is poured is small next to labour, but skipping it costs a sale. The days on site are set by the property itself: the depth of neighbouring Brixton foundations decides how deep the new footings go.
Will my Brixton extension need planning permission or is it permitted development?
Many single storey rear and side-return extensions in SW2 are permitted development, but conservation area status, previous extensions or a larger footprint can require a full planning application to Lambeth Council. Double storey schemes almost always need permission. We check your rights before design work starts and coordinate any application with your architect or designer.
Can I extend a ground-floor flat in Brixton under permitted development?
No. Householder permitted development rights cover houses only; flats and maisonettes have none, so a rear extension to a ground-floor flat needs a planning application to Lambeth Council. With 80% of Brixton dwellings being flats, check this early. Your lease will normally make structural work conditional on the freeholder's written agreement as well, and building regulations approval applies either way.
What happens if a public sewer runs under my Brixton extension site?
Terraced houses in SW2 often share a drain running behind them, and where it is a public sewer, building over or near it needs Thames Water's consent before work starts. A drain survey early on shows its line and depth. Manholes inside the new footprint may need moving or a sealed cover, and new drainage is laid to Part H falls before the floor slab goes down.
How deep do extension foundations go on Brixton's London clay?
Deeper than on gravel, because clay moves as it wets and dries. Building control sets the minimum, and depth increases where trees stand nearby, since their roots draw moisture from the ground. If you dig within 3 metres of a neighbour's house and below its footings, a Party Wall Act notice is due one month before excavation. The inspector sees the open trench before any concrete is poured.
What building control inspections does a Brixton extension go through?
The inspector visits at set stages: open foundation trenches, drainage before backfilling, the damp-proof course and floor, the steel opening into the house, and completion. Insulation in walls, floor and roof must meet current Part L standards, so the roof build-up is checked before it is covered. Book each visit ahead, because nothing should be closed in until it has been seen.
Does the Brixton conservation area have an Article 4 direction on external alterations?
It is not among the areas Lambeth names. Lambeth lists all or parts of Albert Square, Hyde Farm, Lansdowne Garden, Leigham Court Estate, Park Hall Road, St Marks, Stockwell Park, Streatham Lodge and Vauxhall conservation areas as having Article 4 Directions on external alterations. Brixton is not on that list, though conservation area status still applies. We check the address against the list and the current boundary, because a house near the edge of one area can sit in another.
Is a two storey Brixton extension charged differently by Lambeth building control?
Yes. Lambeth lists a single storey domestic extension up to 40m2 and a two storey domestic extension up to 40m2 as separate items, each with its own total charge. If a Brixton scheme gains a bedroom over the new kitchen during design, the building control application is updated to match before work starts. That way the inspections and the completion certificate cover the extension that is actually built, which is what a buyer's solicitor will check.
Can a Brixton rear extension include a room dug below the garden?
Possibly, but the garden sets the limit. Lambeth's Local Plan basement policy wants, generally, at least 70 per cent of a rear garden left with nothing built beneath it before it backs a basement reaching past the house. Behind a Brixton closet wing the yard is often short, so a sunken room under the new extension is checked against that garden area first. If the numbers do not work, the extension stays at ground level and the space is found elsewhere.
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