Flat Conversions Barnet

Flat conversion in Barnet means splitting a house into self-contained flats, or putting a converted house back together as one home. The borough is already split evenly, with 50% of homes flats and 50% houses, and the candidates for conversion are the larger period and interwar houses. Splitting a house into flats needs planning permission everywhere, and each new flat has to meet London space standards. The owner's designer or agent secures the consent, and we build the approved scheme: separation, services and finishes.

In Barnet, 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 Barnet: 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 Barnet houses are split into flats

The houses that make workable flats in Barnet are the bigger ones. The VOA figures show 20% of homes built before 1919 and 34% between 1919 and 1939, and 30% of all homes are semi-detached or detached. A tall Victorian or Edwardian house with generous ceilings divides floor by floor more easily than a two-storey interwar semi, where the stair, the landing and the low roof space leave little room for a second self-contained home.

Planning permission is always needed to turn one house into two or more flats, and Barnet Council decides it against its Local Plan. The Planning Data record for the Barnet Local Plan gives a start date of 2025-03-04, so the designer checks the current policies on conversions and the loss of family homes before drawing. The London Plan counts residential conversions among the small-site intensification it supports where they add net housing, which is the case a conversion has to make.

Housing in Barnet

On the valuation list Barnet counts about 160,480 homes, 50% flats and 50% houses; 20% predate 1919, 34% are interwar and 46% post-war. Where many homes are flats, a flat in Barnet 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 for a house split into flats in Barnet

A self-contained flat created by conversion counts as a new dwelling, so the London Plan space standards apply to it. Policy D6 sets a one-bedspace single bedroom of at least 7.5 square metres and 2.15m wide. A double or twin bedroom needs at least 11.5 square metres. The policy also asks for a floor to ceiling height of 2.5m over at least 75 per cent of each dwelling's internal area. These are planning standards, so they are checked at application stage rather than by building control.

Those numbers decide whether a Barnet house makes two flats or three, and where the bedrooms go. Ceiling height is often the constraint in a top floor under the roof slope or a lower ground floor. Policy D6 also prefers dual aspect flats, which favours splitting a house floor by floor rather than front and back. Your designer tests the layout against the standards before submission, and we build the partitions to the dimensions on the approved plans.

Fire separation and sound insulation between the new Barnet flats

Once a Barnet house becomes flats, every floor between them has to stop fire and sound. Approved Document E sets the lower performance for flats formed by material change of use: 43 dB airborne for walls, floors and stairs, and 64 dB maximum impact for floors and stairs. In a period house with timber joists, meeting that usually means a resilient ceiling below, dense insulation in the void and a floating floor above.

Fire separation under Part B runs alongside it. The common stair becomes a protected escape route, flat entrance doors become fire doors with self-closers, and service penetrations through floors are fire stopped. Part L applies to the new thermal elements and Part M or K to stairs and entrances where they change. We build and test in that order, so the pre-completion sound test and the final building control inspection happen before anyone moves in.

Meters, addresses, CIL and going back to one Barnet house

Each new Barnet flat needs its own electricity supply, meters, heating and usually a separate water supply, which means new risers from the incoming mains and early applications to the network operators. The owner applies to Barnet Council for street naming and numbering so each flat has its own address. Barnet's revised Community Infrastructure Levy charging schedule came into effect on 1 April 2022, and it sets a residential rate covering C3 use, so the designer checks whether a conversion is liable.

Where new floors or beams bear on a party wall, the building owner serves notice under the Party Wall Act, and we cut in only once the neighbour's written consent or an award is in place. A structural engineer designs any strengthening. The reverse job can arise in Barnet too: combining flats back into one family house. That removes the second kitchen, the separate meters and the fire lobby, and reopens the staircase. Because the number of homes falls, planning permission is normally needed, so the designer checks the policy first.

• Separate gas, electricity and water supplies for each flat
• Common hallway, stair and entrance finishes
• House to flat conversions into two or more self-contained units

VOA Council Tax stock of properties, March 2025, for all 42 statistical areas in Barnet. Counts rounded by the VOA.

When comparing flat conversions in Barnet with other work, it helps to read structural alterations in Barnet, our Barnet area guide, builders in Barnet, renovations across London, flat conversions across London and Central Heating Installation Cost.

Why Choose GS Renovation in Barnet

We build conversions to the consented drawings, so the finished building is ready for building control and the sound test. We build any new beams or floor strengthening to the structural engineer's design, and we coordinate the separate supplies, meters and the fire alarm installer. You get one programme covering strip-out, separation, services and finishes, with test results and certificates gathered before handover so the flats can be sold or let.

• Neighbours given notice before the noisy stages
• Separate meters, supplies and consumer units arranged for every flat
• Mains-wired, interlinked smoke and heat alarms to the approved fire strategy

Reviewed jobs near Barnet

2 MyBuilder reviews from Barnet, with each customer's own job title:

• Install new kitchen, Barnet, 15 Apr 2022 (5 out of 5)
• Bathroom Refurbishment, Barnet, 14 Oct 2021 (5 out of 5)

Read all 31 on our reviews page.

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.