House Extensions Dulwich

GS Renovation builds extensions across Dulwich to your designer's approved drawings, from side-return infills and kitchen extensions on the East Dulwich terraces to full wraparound ground floors on the larger SE21 houses. Working on the area's bay-fronted Victorian and Edwardian houses, backed by our founder's 30+ years on the tools, we handle foundations, steelwork, roofing and the full fit-out as a single, accountable project near Dulwich Park.

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

Side-return and rear extensions in Dulwich

The classic Dulwich extension fills in the side return, that narrow strip of dead space beside the rear closet wing, to widen a cramped kitchen into a proper open-plan kitchen-diner. We combine this with a rear extension to push the whole ground floor back into the garden. The existing rear wall usually comes out on a steel beam, sized by an engineer and signed off by building control, which opens the new space fully to the light. Most kitchen extensions in Dulwich take exactly this form: a side-return infill, a rear extension, or a wraparound combining the two, so the kitchen, the dining table and a garden door end up in one room. A single-storey rear room extension for a playroom or study follows the same permitted development or planning route.

These are old houses on shallow footings, so we start with proper foundations and groundworks, checking for existing drainage runs and the proximity of the neighbour's boundary. On the East Dulwich terraces the plots are narrow and the walls are shared, so the Party Wall etc. Act 1996 usually applies where we build up to or astride the boundary. You serve the notices as building owner (or your surveyor does), early, and we give you the drawings they need so everything stays on programme.

Housing in Dulwich

Dulwich counts roughly 14,360 homes for Council Tax; 56% are older than 1919, 11% interwar and 30% post-war, with 55% flats and 45% houses. Where most homes are flats, a flat in Dulwich has no householder permitted development rights, so extending one needs planning permission and the freeholder's consent.

Garden share, depth and fee bands for a Dulwich extension

Southwark's Householder SPD sets the tests that size a Dulwich rear extension before design taste comes in. A terraced or semi-detached home can be extended to the rear by up to 3m in depth with a maximum height of 4m, and rear extensions must not take up more than 50% of the total rear garden space. The SPD says that route is not available to flats, maisonettes or homes in a Conservation Area, although national rules keep it for a house in a conservation area unless a direction removes it. The garden test catches short plots and houses with an existing outbuilding, so measure the garden and everything standing in it first.

Size matters at building control too. Southwark's final fees and charges schedule has one charge for an extension less than 40sqm and a higher one for an extension between 40 and 60sqm, both shown before VAT. A wraparound on a Dulwich semi can land close to that 40sqm line, so a small change in footprint at design stage can move the job into the next band. Ask the designer for the floor area as drawn and check which line of the schedule applies before the application goes in.

Planning and permitted development in SE21

Whether your extension is permitted development or needs a full planning application to Southwark Council depends entirely on your property. Many single-storey rear extensions of a modest size fall under permitted development, while larger footprints, double-storey work, anything facing the street, a side extension in a conservation area, or a home that has already used its allowance will need permission from the council. We assess your house honestly before you commit.

Where permission is required your architect or designer prepares and submits the application, and where the work is permitted development a lawful development certificate gives certainty when you sell. We build to the approved drawings. Either route, the structural side still needs building control approval under the Building Regulations, which is separate from planning, and we coordinate the building control inspections so the two approvals never trip each other up.

Kitchen extensions in Dulwich

55% of homes in Dulwich 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. Most kitchen extensions here are on the 45% of homes that are houses. The fit-out is priced on its own page, kitchen renovation in Dulwich; the build figures are in the table above.

Double storey extensions in Dulwich

Under permitted development a two-storey rear extension can go no more than 3 metres beyond the original rear wall and must stay at least 7 metres from the rear boundary, and in a conservation area it is not permitted development at all. Many gardens are too short for the 7 metre rule, so a double storey extension in Dulwich often needs planning permission from Southwark Council. On the 29% of homes that are terraced, the neighbours' windows usually decide the depth. The Sunray Estate in North Dulwich is subject to an Article 4 Direction confirmed by the Secretary of State on 13 November 1987 (council source). Our double storey extension page explains the build, at £1,800 to £2,600 per m² across both floors.

• Insulation, airtightness and thermal detailing to regulations
• Trial holes to set foundation depth near drains and trees
• First fix and second fix plumbing and electrics throughout

VOA Council Tax stock of properties, March 2025, for North Dulwich, East Dulwich, Herne Hill & Dulwich Park and Dulwich Hill. Counts rounded by the VOA.

If this is your first project in Dulwich, these are worth a look: RSJ and steel beam installation in Dulwich, house extensions across Southwark, side return infills, garage conversions in London, house extensions across London and Crittall Doors Guide.

The GS Renovation Difference in Dulwich

Dulwich homeowners choose GS Renovation because we run the whole extension, groundworks to final coat, with one team that knows how SE21 terraces behave. We are straight with you about whether the job is permitted development or needs planning from Southwark Council, we coordinate the work around the party wall award, and our founder's 30+ years on the tools means fewer surprises once the foundations are dug.

• Programme planned around party wall notice periods before excavation near a neighbour
• Clean, tidy and reliable tradespeople
• Insulation and thermal detailing to current regulations

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.