Flat Conversions Mitcham

Flat conversions in Mitcham start with Merton's rule on family homes. Splitting a house into self-contained flats needs planning permission, and Merton Local Plan Policy D12.10 requires a conversion of a 3-bed or larger house into two or more units to re-provide at least one family-sized home. With 40% of Mitcham homes being terraced houses, that rule shapes which houses can be split at all. We build the conversion your designer has drawn and the owner has consent for.

In Mitcham, 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 Mitcham: 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.

Splitting a Mitcham house under Merton's family housing rule

Policy D12.10 is the first test for any Mitcham house conversion: a family-sized home of three bedrooms or more that becomes two or more units must still include at least one family-sized home. On a two storey interwar terrace, keeping three bedrooms in one unit and fitting a second flat is hard, so larger or already extended houses are the realistic candidates. The owner or their designer applies for the planning permission that the change to flats needs.

Merton's Local Plan also says every dwelling conversion, whatever its size, must rigorously apply the space standards in London Plan Policy D6. That includes a minimum floor to ceiling height of 2.5m over at least 75 per cent of each flat's Gross Internal Area. In a Mitcham house, a low back addition or a room under a sloping roof counts against that 75 per cent, so we measure every ceiling during the survey and give the figures to your designer.

Housing in Mitcham

Mitcham's housing, as the Council Tax list records it, is about 10,560 homes: 53% houses, 46% flats, with 10% pre-1919, 38% interwar and 51% built since 1945. Terraced houses make up 40% of homes here, and a converted terrace in Mitcham has two party walls to consider for sound.

Room sizes, outdoor space and aspect in a converted Mitcham flat

London Plan Policy D6 sets the room sizes the new flats in Mitcham must meet. A single bedroom needs at least 7.5 square metres and 2.15m of width, and a double or twin at least 11.5 square metres. When a front bedroom in a terrace is split to create a hallway for the upper flat, what is left can fall below those sizes. Your designer tests the plan against them, and we set out the new stud walls from the approved drawings.

Policy D6 also asks for at least 5 square metres of private outdoor space for a 1 to 2 person dwelling where the borough sets no higher standard, and says single aspect homes should normally be avoided. In a Mitcham terrace the garden often goes with the ground floor flat, so the upper flat's outdoor space is a design question for your designer. These space standards sit in planning, not in the building regulations, so they are settled before we price.

Fire and sound separation between the new Mitcham flats

Building regulations treat the new flats as separate dwellings, so the floor between them and the walls to the shared stair need fire resistance and sound insulation. Approved Document E sets performance for flats formed by material change of use at 43 dB airborne for walls and floors and 64 dB maximum impact for floors. In a timber floor we add a resilient layer, mineral wool and an independent ceiling to reach those figures.

Flats formed by a material change of use need pre-completion sound testing to show the floors and walls meet the standard, so we build the test into the programme before decoration. On an interwar Mitcham house the chimney breasts and old floorboards leak sound, and those gaps are sealed before the ceiling goes up. Fire doors to each flat, a protected route to the front door and linked alarms complete the separation, and your structural engineer checks any new trimming of the stair opening.

Flood zones, levies and separate services on a Mitcham conversion

Policy D12.10 adds a flood test: dwelling conversions in Flood Zone 3b must not increase the building footprint or the number of units or bedrooms. Before anything else, your designer checks which flood zone the Mitcham house sits in, because in that zone a split into more flats cannot go ahead. Outside that zone, the family housing and space tests covered above are what shape the room layout and the number of flats.

A permission for any new dwelling in Merton will usually become liable for the Community Infrastructure Levy, so a conversion that adds a flat is likely to fall within CIL, and the owner confirms the amount with Merton. Each new flat also needs its own gas and electricity meters, water supply, consumer unit and postal address through street naming and numbering. Where a party wall is cut into, the building owner serves notice under the Party Wall Act before we start that work.

• Separate gas, electricity and water supplies for each flat
• Decoration, flooring and making good throughout, ready to let or sell
• Flats converted back into a single family house

VOA Council Tax stock of properties, March 2025, for Mitcham East, Mitcham West and Mitcham South. Counts rounded by the VOA.

Two or three things usually come up alongside flat conversions on a Mitcham job: structural alterations in Mitcham, flat conversions across Merton, builders in London who take on conversions, party walls in a flat conversion, flat conversions anywhere in London and House Rewire Cost.

Why Mitcham Homeowners Choose GS Renovation

A flat conversion in Mitcham touches planning, building control and the title, and each sets part of the build. We take the approved drawings and conditions and turn them into a programme where the separating floor, the fire doors, the new services and the sound test happen in the right order. Your structural engineer covers any change to the floors or stair, a registered electrician certifies each flat's electrics and a Gas Safe engineer carries out the gas work.

• Separate meters, supplies and consumer units arranged for every flat
• Each flat numbered and supplied before the keys are handed over
• Registered in England, Companies House no. 14611254

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.