Flat Conversions Merton

Converting a house into flats in Merton is governed by a clear local rule: Policy D12.10 says a family-sized home of three bedrooms or more split into two or more units must re-provide at least one family-sized home. That shapes every layout before space standards, fire separation and sound insulation come in. Terraced houses are 43% of homes, and larger Victorian and Edwardian houses are the obvious candidates, which often suits a family maisonette plus one smaller flat. The owner or designer secures the planning permission; we build to it.

In Merton, 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 Merton: 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.

Merton's family home rule for splitting a house

In Merton a conversion has to keep a family home in the building. Splitting a house into flats is a change of use that needs planning permission, and Local Plan Policy D12.10 requires a conversion of a 3-bed or larger home into two or more units to re-provide at least one family-sized home. On a tall terrace that often points to a ground floor maisonette with the garden, and a smaller flat above with its own front door off the shared hall.

The same policy limits where units can be added. Under Policy D12.10, dwelling conversions in Flood Zone 3b must not increase the building footprint or the number of units or bedrooms, so a house in that zone cannot be split into more homes. The London Plan counts residential conversions as small-site intensification where they add net housing. Your designer checks the flood zone and the policy before the drawings are drawn, and our price follows the scheme that can actually be approved.

Housing in Merton

The Council Tax list puts Merton at about 87,830 homes, 42% flats against 58% houses; 26% went up before 1919, 37% between the wars and 36% after 1945. 43% of homes here are terraced; a converted terrace in Merton has two party walls to consider for sound.

Space standards that set the Merton flat layout

The Local Plan says every dwelling conversion in Merton, whatever its size, must rigorously apply the space standards in London Plan Policy D6. Under that policy a single bedroom must be at least 7.5 square metres and at least 2.15m wide, and a double or twin must be at least 11.5 square metres. In a Victorian terrace the back bedroom can fall short once a new partition and a lobby are added, so every room is checked on the survey drawings before the layout is fixed.

Ceiling height matters as much as floor area. Policy D6 sets a minimum floor to ceiling height of 2.5m for at least 75 per cent of each dwelling's internal area, and asks for dual aspect flats where possible. That rules out a lot of low attic space in a Merton house, and it means we avoid dropping ceilings too far when boxing in new soil pipes. The space standard sits in the planning system, not the Building Regulations, so the approved drawings are what we build to.

Fire and sound separation between Merton flats

Flats formed by a material change of use, in Merton as anywhere in England, have to meet Approved Document E: 43 dB airborne sound insulation for walls, floors and stairs, and 64 dB maximum impact for floors and stairs. The floors between flats carry most of that work. On a timber floor that means a new ceiling on resilient bars, acoustic insulation between the joists and a floating layer above, with the separating walls and floors tested before completion.

Fire separation under Part B follows the same floors and the shared hall. Each flat needs a protected escape route, a fire door onto the common hall, sealed service penetrations and the linked alarms the approved plans set out, and we keep the fire stopping visible until it is inspected. Merton's building notice route is for domestic projects, but a house split into flats with shared common parts falls under fire safety law, so plan on a full plans application. Merton decides those within five weeks, or up to two months if agreed.

Meters, addresses, party walls and CIL on a Merton conversion

Each new flat in Merton needs its own services, and the utilities take longer than the building work. Separate electricity and gas meters, a water supply that can be metered per flat, and new addresses through the council's street naming and numbering all need applying for early. We set out the meter positions, the incoming supply routes and the risers on the drawings, so the utility firms connect to work that is ready.

Two other points belong in the budget. If new steel or a separating wall is built on or cut into a party wall, the Party Wall Act applies, and the building owner serves notice on the neighbour before that work starts. Merton says a permission for any new dwelling will usually become liable for CIL, so ask your designer to check the charge and any relief before the start date is fixed.

• Bin stores, cycle stores and external works to the planning conditions
• Fire stopping round every pipe and cable through a separating floor
• Flats converted back into a single family house

VOA Council Tax stock of properties, March 2025, for all 25 statistical areas in Merton. Counts rounded by the VOA.

Work in Merton rarely sits on its own, so you may also want structural alterations in Merton, our Merton area guide, a building contractor for the whole conversion, the Party Wall Act when a conversion cuts a shared wall, flat conversions across London and Who Pays the Party Wall Surveyor.

Trusted Flat Conversions in Merton

A conversion goes wrong when the drawings, the planning consent and the building control approval drift apart on site. We price from the approved drawings, walk the building with you and your designer, and flag any room that would fall below the standard before a wall goes up. One team handles the strip out, the new floors and partitions, the separation work and the finishes, and co-ordinates the electrician, plumber and alarm installer so each flat is completed and handed over as a unit.

• Full plans application to building control, never a building notice
• Founder with 30+ years of hands-on experience
• Fire strategy for the stair and each flat entrance settled before strip-out

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.