Flat Conversions Belgravia

Flat conversion work in Belgravia runs in both directions. VOA figures for the wider Knightsbridge, Belgravia & Hyde Park area count 71% of homes as flats and 28% as terraced houses, and some of those flats sit in tall townhouses split long ago. Some owners now want a house divided into self-contained flats to current standards, while others want a building put back together as one house. Either way planning permission comes first, followed by the London Plan space standards and the Building Regulations on fire and sound separation between flats.

In Belgravia, 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 Belgravia: 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.

Space standards for a new flat in a Belgravia townhouse

A new flat formed in a Belgravia townhouse needs planning permission, because subdividing a house is a material change of use. It also has to meet the London Plan minimum space standards, which count conversions and change of use as new dwellings. Under Policy D6 a single bedroom must be at least 7.5 square metres and at least 2.15m wide, and a double or twin bedroom at least 11.5 square metres. Westminster also charges CIL on new dwellings of any size, so your designer or agent checks the levy position, including any offset for existing floor space, before the application.

Height is the harder test in the upper storeys of a Belgravia house. Policy D6 sets a minimum floor to ceiling height of 2.5m for at least 75 per cent of the Gross Internal Area of each dwelling, which the tall first floor usually meets and a converted attic storey may not. Policy D6 also asks developments to maximise dual aspect homes and normally avoid single aspect ones. A tall terrace with front and back windows helps here, provided the plan runs each flat from front to rear.

Housing in Belgravia

The Knightsbridge, Belgravia & Hyde Park statistical area's housing, as the Council Tax list records it, is about 6,020 homes: 29% houses, 71% flats, with 67% pre-1919, 9% interwar and 23% built since 1945. Since most homes here are flats, a flat in Belgravia can be split or combined only with the freeholder's consent, and changing the number of homes usually needs planning permission as well.

The plans a Belgravia conversion is judged against

A Belgravia conversion is assessed against Westminster's development plan, and two parts of it are recent. The current City Plan was adopted by full council on 21 January 2026 after a Partial Review, and the Belgravia Neighbourhood Plan was adopted on 7 March 2024. Your designer or agent reads both before drawing the flats, because they decide how many units the house can take and what it must keep. Belgravia is also a conservation area, so new entrances, meter boxes, bin stores and rooftop plant are part of the planning drawings.

The London Plan treats residential conversions as a form of small-site intensification where they add homes, which is the case a Belgravia application makes. The Nationally Described Space Standard is not a building regulation and sits within the planning system, so the room sizes are fixed at the planning stage and the building control application then deals with fire, sound and energy. Each new flat needs its own electricity supply and meter, its own water and heating, and a postal address from street naming and numbering before the flats are sold or let.

Fire and sound separation between new Belgravia flats

Separation is the core of a Belgravia conversion, because each new flat has to be protected from the one below and from the shared stair. A material change of use brings Part B into play. The stair becomes a protected escape route, the floors between flats are upgraded to the fire resistance the designer specifies, and each flat gets a fire-resisting entrance door and its own detection. Old lath and plaster ceilings are rarely enough alone, so the upgrade is built from below or above to the agreed specification.

Sound is the other half. Approved Document E sets lower performance for flats formed by material change of use: 43 dB airborne for walls and for floors and stairs, and 64 dB maximum impact for floors and stairs. In a Belgravia townhouse with deep timber floors the usual build-up is a resilient ceiling below and mineral wool in the void, with a floating floor above where the ceiling alone will not reach the figures. An ornate plaster ceiling below can rule out the first option. Pre-completion sound testing is booked in, so any failing floor is found before decoration.

Turning Belgravia flats back into a single house

Putting a Belgravia townhouse back into one house is a conversion in reverse, and it needs the same care over structure and services. The flat partitions are stripped out, redundant kitchens and bathrooms are removed, and the stair, where it was boxed in as a fire-protected common route, can be opened up again once it serves a single home. Each duplicated service is traced back to one supply and one heating system, and the suppliers are asked to merge the meters.

Planning comes first, and it sits with your designer. Merging flats reduces the number of homes, which planning policy generally protects, so the planning position is settled before we start. Belgravia is a conservation area, first designated in 1968, so taking out the extra doorbells, meter boxes and bin stores the flats added is part of the same application. We build to the consent once it is granted, and the Belgravia layout can then return to the full-height rooms the house was designed with.

• House to flat conversions into two or more self-contained units
• Pre-completion sound testing arranged before sign-off
• Heating and hot water for each flat, gas by a Gas Safe registered engineer

VOA Council Tax stock of properties, March 2025, for the Knightsbridge, Belgravia & Hyde Park statistical area, which also covers parts of Knightsbridge. Counts rounded by the VOA.

If you are weighing up options for your Belgravia property, it is worth reading structural alterations in Belgravia, flat conversions across Westminster, a building contractor for the whole conversion, the Party Wall Act when a conversion cuts a shared wall, flat conversions anywhere in London and Party Wall Act Explained.

Trusted Flat Conversions in Belgravia

A Belgravia conversion needs a builder who can make fire and sound separation work inside an old timber-floored house without losing its character. We give a written quotation after a site visit, build to your designer's consented drawings, and run the structure, separation, services and fit-out as one programme. The founder has more than thirty years of hands-on experience, and the building control file closes with the sound test results and the electrical and gas certificates in place.

• Dust screens and floor protection in occupied homes
• Fire strategy for the stair and each flat entrance settled before strip-out
• Separating floors built to the acoustic detail the sound test checks

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.