Flat Conversions Hampstead

Flat conversion in Hampstead means turning a period house into self-contained flats, reworking an older split so each flat meets today's standards, or joining flats back into one house. Only 22% of homes across the statistical areas covering Hampstead, Frognal and Fitzjohns are houses and 78% are already flats, so the houses left to convert are the period cottages and substantial Victorian villas. Planning permission always comes first, then Camden's housing mix and size policies, then the building regulations for fire and sound between the new flats.

In Hampstead, 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 Hampstead: 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 Hampstead buildings are converted, and in which direction

The Hampstead buildings that suit conversion are the larger period houses, since only 22% of homes here are houses at all. 11% are terraced and 11% are semi-detached or detached, and 63% of all homes were built before 1919. A tall villa with a raised ground floor, a lower ground floor and a full attic storey can take a flat on each level, with the original staircase kept as the common route. A narrow cottage rarely has the floor area to split well. Splitting a house into flats is a material change of use, so the owner or their designer needs planning permission before we start.

The reverse also happens, and Camden's policy shapes it. Local Plan Policy H3 resists development that would involve the net loss of two or more homes, unless it creates large homes, adapts affordable homes or enlarges sub-standard units to meet space standards. So joining two flats into one maisonette is a different case from folding three flats back into a single house. Your designer tests the proposal against H3 before we price the strip out of the extra kitchens and bathrooms.

Housing in Hampstead

Hampstead counts roughly 11,670 homes for Council Tax; 63% are older than 1919, 10% interwar and 27% post-war, with 78% flats and 22% houses. Where most homes are flats, a flat in Hampstead can be split or combined only with the freeholder's consent, and changing the number of homes usually needs planning permission as well.

Camden's rules on housing mix, size and levy

A new flat conversion in Hampstead has to fit Camden's housing mix. Local Plan Policy H7 requires all housing development, including conversion of existing homes, to contribute to the Dwelling Size Priorities Table and include a mix of large and small homes. Splitting a villa into studios alone will struggle against that. A layout with a family flat on the garden level and smaller flats above answers the policy and uses the garden where it is most useful.

Camden applies the nationally described space standard flexibly to homes created by conversion, taking into account the constraints of existing buildings, particularly listed buildings and heritage assets. That flexibility helps where a chimney breast or a staircase cannot move, but it does not remove the standard. Camden's Community Infrastructure Levy applies to proposals that add an extra dwelling, and Hampstead falls in Zone C. The charge is worked out on net new floorspace, so your agent confirms it, and the forms due before work starts, before you commit.

Space, height and sound between the new Hampstead flats

Each flat must meet the London Plan space standard, which counts conversions and changes of use as new dwellings. Under Policy D6 a single bedroom needs at least 7.5 sq.m and 2.15m of width, a double at least 11.5 sq.m, and at least 75 per cent of each flat's floor area needs a floor to ceiling height of 2.5m. In a Hampstead villa the attic and lower ground floor are the storeys most likely to fall short, so that is where the tape measure decides the layout.

Fire and sound separation are what turn one house into several homes. Approved Document E sets sound insulation for flats formed by change of use at 43 dB airborne for walls and for floors and stairs, and 64 dB maximum impact for floors and stairs. The separating walls and floors are sound tested before completion. On timber joists that means a new ceiling on resilient bars, insulation in the void and a floating floor above. Part B asks for fire separation between flats and a protected common stair, and each penetration is sealed before the ceilings close.

Services, basements and party walls in a Hampstead conversion

Each new flat in a Hampstead conversion needs its own services and its own address. That means a separate electricity supply and meter, a separate gas supply or all-electric heating, and water that can be isolated flat by flat. The supply companies need lead time for new meters, so they are requested as soon as the consent is in hand. Each flat also needs a postal address from the council's street naming and numbering service, and the waste from every new kitchen and bathroom has to reach a stack without crossing another flat.

Lower ground floors and party walls bring their own rules. Camden's Article 4 direction on basements, adopted on 1 June 2017, applies to the whole borough, so digging out a Hampstead lower ground floor to gain height for a flat needs planning permission, with a site-specific Basement Impact Assessment. Where a party wall is cut into for new steel or built up for separation, the Party Wall Act applies and the building owner serves the notices. Camden's basement guidance strongly recommends concluding Party Wall agreements before seeking approval of the Basement Construction Plan.

• Protected escape stairs and fire-rated flat entrance doors
• Separating walls built and lined for sound between flats
• Decoration, flooring and making good throughout, ready to let or sell

VOA Council Tax stock of properties, March 2025, for Hampstead Town, Frognal and Fitzjohns & Royal Free. Counts rounded by the VOA.

Useful next reading for a flat conversions project in Hampstead: structural alterations in Hampstead, flat conversions across Camden, building control sign-off for a conversion, renovations across London, flat conversions across London and Party Wall Act Explained.

The GS Renovation Difference in Hampstead

A conversion is several jobs at once: structure, fire, sound, drainage, new services for each flat and finishes to sell or let. We run them in one sequence so the separating floors and walls are built, sealed and tested before anything is closed in. Your structural engineer designs any new openings or steel, and we build to the planning consent and the building control drawings. You get a programme showing when each flat is ready, and the certificates each one needs at handover.

• Wet rooms stacked floor over floor to keep the drainage simple
• Fire strategy for the stair and each flat entrance settled before strip-out
• Structural engineer instructed and coordinated on your behalf

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.