House Extensions Borough

GS Renovation builds house extensions throughout Borough and SE1, where almost every home is a flat and extensions are limited to the few terraced houses. We handle rear, side-return and wrap-around extensions, from homes near the South Bank to the streets towards Bermondsey.

In Borough, 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 Borough: the structural engineer we appoint designs the structure, we build it, and building control signs it off.

Side-return and rear extensions in Borough

On Borough's few terraced houses, the usual extension fills the side return, the narrow strip of yard beside the rear closet wing where the house has one. Infilling it widens a cramped kitchen into a bright open-plan space, often combined with a rear extension to push further into the garden. We handle the foundations and groundworks, the steel beams that carry the old outside wall, the roof works and the full fit-out as one continuous project.

Borough's houses sit on tight urban plots, so we plan every extension around any existing closet wing, the drainage runs and the party walls with neighbours either side. We match brickwork and detailing where it matters, and we keep the works tidy and contained on the restricted SE1 sites that are typical here. One team stays responsible from the first dig to the final coat of paint.

Housing in Borough

Roughly 12,140 dwellings sit on the valuation list for Borough. 6% are houses and 94% flats, and by age 18% predate 1919, 3% are interwar and 73% post-war. Where most homes are flats, a flat in Borough has no householder permitted development rights, so extending one needs planning permission and the freeholder's consent.

What Southwark's SPD allows behind one of Borough's terraced houses

The VOA records 6% of Borough homes as terraced houses and 0% as semi-detached or detached, so an extension here is built between neighbours. Under Southwark's Householder SPD, a terraced home can go out at the back by up to 3m, no higher than 4m, and the extension may not cover more than 50% of the total rear garden space. On a small Borough yard, that garden rule can decide the footprint before the depth rule does.

Location matters as much as size. Broadly west and south of Borough Tube Station is the Liberty of the Mint Conservation Area. Nationally, a conservation area takes away permitted development for side and two storey rear extensions but leaves a single storey rear extension within the limits. Southwark's Householder SPD says building a single storey rear extension without planning permission is not applicable to homes in a Conservation Area. For a Borough terrace inside that boundary, get the position in writing and allow time for a planning application. Draw garden doors and roof glazing in timber or aluminium, since the SPD excludes UPVC from every conservation area in Southwark, rear elevations included.

A listed building is the exception: work that affects its character, inside or out, including an extension or taking out a wall or chimney breast, needs listed building consent from Southwark Council, and doing it without consent is a criminal offence.

Planning and party walls in Southwark

Whether your extension needs a full planning application to Southwark Council or falls under permitted development depends on the property, its size and whether it sits in a conservation area. On Borough's few houses, many single-storey rear extensions proceed under permitted development, while larger schemes usually need permission, and a flat has no such rights. We assess your home honestly and tell you which route applies.

Alongside planning, the structural side is covered by building regulations, with building control inspecting foundations, steelwork and drainage as the extension goes up. And because you are digging and building close to the boundary in these terraces, the Party Wall Act almost always applies, so you, as building owner, serve notices on adjoining owners, using drawings we supply. We coordinate the planning drawings, building control and the party wall timetable together so nothing is missed.

Kitchen extensions in Borough

94% of homes in Borough are flats, and a flat has no householder permitted development, so a ground-floor flat's kitchen extension needs planning permission from Southwark Council and the freeholder's consent. With so few houses here, the realistic kitchen gain in most Borough homes is a better layout inside the flat rather than an extension. The fit-out is priced on its own page, kitchen renovation in Borough; the build figures are in the table above. Double storey extensions belong to the few houses here.

• Levels, drainage and landscaping made good around the new build
• Insulation, airtightness and thermal detailing to regulations
• Planning applications and permitted development assessments

VOA Council Tax stock of properties, March 2025, for Borough & Southwark Street and Southwark St George's. Counts rounded by the VOA.

If you are weighing up house extensions in Borough, it may help to read RSJ and steel beam installation in Borough, house extensions across Southwark, basement extensions, a garage conversion instead, our London house extensions page and Bifold vs Sliding Doors.

Trusted House Extensions in Borough

Borough homeowners choose GS Renovation because one team takes an extension from groundworks through steelwork, roof and fit-out, coordinating the planning drawings, building control and the party wall timetable alongside. Our founder's 30+ years on the tools means we understand side returns, closet wings and tight plots, delivering extensions that feel part of the original house.

• Drainage diverted or built over with the right approval in place
• Free follow-up visit after completion if anything needs attention
• Building control inspected at foundation, damp course and steel stages

Checked by Abdelaaziz Saaid, founder and director of GS Renovation Ltd (Companies House no. 14611254). Structural design is by the consulting engineer appointed to your project.