Flat Conversions Dulwich

Converting a house into flats in Dulwich starts with a size test. Southwark Plan 2022 Policy P3 does not allow a single home of 130sqm or less original net internal floorspace to be split into two or more homes. So the first question for a Dulwich villa or terrace is its original floor area, not its number of bedrooms. Where a scheme gains planning permission, we build the fire and sound separation, the new services and the finishes to the approved drawings, and we also join flats back into one house.

In Dulwich, converting a house into two or three flats is published at £50,000 to £120,000 including professional and council fees, and an England-wide guide puts a straightforward two-flat split at £40,000 to £80,000 in construction alone, which is the part a builder prices (indicative London ranges, Architectural Drawings and Mayfair Studio, 2026). GS Renovation Ltd, a building contractor based in Potters Bar, does the work in Dulwich: we build the conversion to the approved drawings, building control inspects the fire and sound separation, and a registered electrician certifies each flat's electrics.

Which Dulwich houses can be split into flats

Size decides before layout does. Policy P3 in Southwark Plan 2022 protects existing family housing from conversion into smaller homes unsuitable for families, and it sets a floor: a single dwelling with 130sqm or less of original net internal floorspace cannot be subdivided. The test is the original floorspace, so measure the house as first built, not as later extended. On VOA figures for the wider Dulwich and Herne Hill wards, 29% of homes are terraced houses and 16% semi-detached or detached. Whether a given house clears the line depends on its measured area, so check it before paying for a layout.

Get the numbers right early, because they drive the whole project. Dividing a house into flats is a material change of use, so it needs planning permission as well as building regulations approval. The planning drawings need to show the original floor area, each proposed flat's area against the minimum room sizes and how any family-sized flat reaches the garden. If the house is under the threshold, the realistic option is a better single home. We read the approved drawings closely before pricing, because consent conditions can set details such as refuse storage, cycle parking and sound testing.

Housing in Dulwich

By the valuation list's count, Dulwich holds about 14,360 homes, 45% houses and 55% flats; by age, 56% were built before 1919, 11% between the wars and 30% since 1945. Since most homes here are flats, a flat in Dulwich can be split or combined only with the freeholder's consent, and changing the number of homes usually needs planning permission as well.

Space standards and ceiling heights for Dulwich conversions

Every new flat has to meet the national minimum space standards. Southwark Plan 2022 Policy P15 applies them to new homes including conversions, and the London Plan confirms that conversions and changes of use count as new dwellings. Under London Plan Policy D6 a single bedroom must be at least 7.5 square metres and 2.15m wide, and a double at least 11.5 square metres. In a Dulwich villa the pinch points are the small rear bedrooms over the closet wing and the attic rooms under the roof slope.

Height is the harder test in an old house. Policy P15 also asks for a floor to ceiling height of at least 2.5 metres over at least 75 per cent of each flat's gross internal area. Victorian ground and first floors can clear that, while an upper storey or a lower ground floor may not, and lowering a floor or raising a ceiling is structural work with its own cost. We check ceiling heights room by room at survey, so the layout you take to planning is one that can be built in the Dulwich house you own.

Fire and sound separation between flats in a Dulwich house

The floors and walls between flats are where a conversion succeeds or fails. Approved Document E sets the minimum sound performance for flats formed by a change of use: 43 dB airborne for separating walls and floors, and a maximum of 64 dB impact through floors and stairs. In a Dulwich house with timber joist floors, that means a new ceiling on resilient bars below, dense insulation between the joists and an acoustic layer above, all tested on completion. Fire separation follows the same lines under Part B, with a protected stair, fire doors to each flat and fire stopping at every service penetration.

Each flat then needs its own services and identity. That means a separate electricity meter and consumer unit, a separate heating system or boiler, water supplies the utilities will accept, and a new address from Southwark's street naming and numbering team. Where the work cuts into or builds on a party wall with the house next door, the Party Wall Act applies, and Southwark's Householder SPD notes that a Party Wall Agreement is separate from planning permission. The building owner serves the notices, two months ahead for a party structure notice, and that part of the Dulwich job starts on written consent or a surveyor's award.

Outdoor space, aspect and joining Dulwich flats back into a house

The London Plan counts residential conversions among the small-site changes that add homes, but it asks for good homes, not just more of them. Policy D6 asks for dual aspect flats where possible, and where borough plans set no higher standard, at least 5 square metres of private outdoor space for a 1 to 2 person flat plus 1 square metre for each additional occupant. In a Dulwich villa that usually means giving the garden to the ground floor flat and finding a terrace or balcony for the flats above.

Some Dulwich owners go the other way and join flats back into one house. The build is often simpler than the original split: removing the extra kitchen, reopening the stair, taking out fire lobbies and bringing the services back to one supply. Southwark Plan 2022 Policy P3 is titled Protection of existing homes, and joining flats reduces the number of homes, so ask Southwark early whether permission is needed. On site, merging undoes separations building control approved, so the stair, doors and alarm are rethought for one household.

• Separate gas, electricity and water supplies for each flat
• Steel beams and new openings built to the engineer's design
• Insulation to the walls, roof and floors the conversion touches

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 you are weighing up options for your Dulwich property, it is worth reading structural alterations in Dulwich, flat conversions across Southwark, a building contractor for the whole conversion, refurbishing a flat that has already been converted, our London flat conversions page and Party Wall Act Explained.

Why Choose GS Renovation in Dulwich

A conversion depends on detail that is hidden once finished: separation floors, fire stopping and services routed to each flat. We build to the approved drawings and the building control plans, arrange the pre-completion sound testing, and hand over the completion paperwork your lender or buyer will ask for. The founder, Abdelaaziz Saaid, has more than three decades of hands-on experience, and you get one programme and one point of contact.

• Full plans application to building control, never a building notice
• Our own trades on site rather than a chain of subcontractors
• Each flat numbered and supplied before the keys are handed over

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.