Flat Conversions Balham
Houses divided into self-contained flats in Balham, separating floors, a protected stair and separate services for every flat.
- Rated 4.9 from 31 reviews on MyBuilder
- London guide: £50,000 to £120,000
- Free site survey, itemised quote
Converting a Balham house into flats starts with Wandsworth's policy on protecting family homes. The Local Plan, adopted on 19 July 2023, protects the existing self-contained housing stock and limits the conversion of single dwellings into flats through policies LP25 and LP26. Terraced houses, 37% of homes in the VOA count for the wider Balham and Nightingale Lane area, are the obvious candidates, so the planning case comes before the builder's plan. We build the separation, services and finishes to the consent your designer secures.
In Balham, 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 Balham: 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.
Price guide
| Work | Indicative range |
|---|---|
| House into 2 to 3 flats in London, fees and build (Architectural Drawings) | £50,000 to £120,000 |
| Build cost per square metre, London (Architectural Drawings) | £1,000 to £2,000 |
| House into 2 flats, construction only, England-wide guide (Mayfair Studio) | £40,000 to £80,000 |
| Sound insulation and fire separation, England-wide guide (Mayfair Studio) | £5,000 to £15,000 |
| Separate utility connections, 3 flats, London (Architectural Drawings) | £3,000 to £6,000 |
Indicative ranges from published cost guides (Architectural Drawings and Mayfair Studio, 2026), not a quotation. Each row names its source and whether it is a London, UK or England-wide figure. Prices checked September 2026.
Quick estimate from published guides
Guide range: choose above
Wandsworth's policy on splitting a Balham house
Splitting a Balham house into flats is a policy question first, because Wandsworth's Local Plan limits the conversion of single dwellings into flats through policies LP25 and LP26. The plan, adopted on 19 July 2023, protects the existing self-contained housing stock. The London Plan lists residential conversions among the forms of incremental intensification where they add net housing, but the local policies set the tests a Balham scheme has to meet.
Planning permission is always needed, because using one house as two or more homes is a material change of use in planning law. That is why the drawings matter before anyone prices the build. The owner's designer or planning agent sets out how the scheme meets LP25 and LP26, and whether the house qualifies as family housing Wandsworth wants kept. We then price and programme from the approved layout. If the consent limits the number of units, the structural and services plan changes with it.
Housing in Balham
The Council Tax list puts Balham at about 7,240 homes, 55% flats against 45% houses; 68% went up before 1919, 8% between the wars and 24% after 1945. Since most homes here are flats, a flat in Balham 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 new flats in Balham
Every new Balham flat, including one formed by conversion, has to meet the London Plan space standards. The minimum internal space standards table states that a new dwelling includes conversions and change of use, and Policy D6 applies the standards to all tenures. Wandsworth adds that residential development must meet the housing standards in Local Plan policy LP27, including private internal space and daylight. A layout that squeezes an extra unit into a Balham terrace by trimming rooms below the standard fails the test your designer has to meet.
Under Policy D6 a single bedroom must be at least 7.5 square metres and 2.15m wide, a double at least 11.5 square metres, and at least 75 per cent of each flat needs a floor to ceiling height of 2.5m. In a Balham terrace the top floor under the roof slope and the back addition are where those figures bite. Your designer tests the layout against them before we set out a single stud wall.
Party walls, meters and addresses for Balham flats
A Balham terrace conversion can cut into the party walls, for new steel bearings, a relocated stair or a chimney breast taken out to fit a kitchen. Wandsworth's own party walls page treats these as matters between adjoining owners and points you to the government's explanatory booklet. As building owner you serve the notices, or your surveyor does, before that work starts. We give the surveyor our method and sequence, and keep the neighbour's side protected.
Each new Balham flat also needs its own services and identity. That means a separate electricity meter and consumer unit, a separate gas supply or electric heating, and a water supply that can be isolated per flat. Drainage from each kitchen and bathroom connects to the stack without passing through a neighbour's flat where possible. New flat numbers come through the council's street naming and numbering process, which the owner applies for, and utilities usually want the new addresses before fitting meters.
Fire and sound separation between Balham flats
The floors and walls between new Balham flats have to stop fire and sound, and in a Victorian terrace that means upgrading them, not just redecorating. Approved Document E sets the performance for flats formed by material change of use at 43 dB airborne for walls, floors and stairs, and 64 dB maximum impact for floors and stairs. Those figures shape the whole build up of every separating floor in a Balham conversion, so they are priced from the start.
Old joisted floors with lath and plaster ceilings rarely reach that without work. We lift boards, add mass and resilient layers, insulate the voids and form a new ceiling below, then build the Part B fire separation around the shared stair so each flat has a protected escape route. Pre-completion sound testing checks the result. The registered electrician certifies each flat's installation separately, and the building control completion certificate covers the whole conversion.
- Fire detection in every flat and the common hall, laid out to the fire strategy
- Fire stopping round every pipe and cable through a separating floor
- Decoration, flooring and making good throughout, ready to let or sell
VOA Council Tax stock of properties, March 2025, for Balham and Nightingale Lane. Counts rounded by the VOA.
Why Balham Homeowners Choose GS Renovation
You get a builder who can carry a conversion from the strip out through the new floors, stairs, fire and sound separation and the separate services, to finished flats. We work from your designer's consented layout and the structural engineer's details, give you a written programme with each building control stage marked, and keep the order of work tied to the tests that have to pass. The planning and consent applications stay with you or your agent; we supply the method statement and programme they need.
- Wet rooms stacked floor over floor to keep the drainage simple
- Separating floors built to the acoustic detail the sound test checks
- Waste cleared as we go, not left piled up outside
George was brilliant. Lovely bloke, very reasonably priced and a perfectionist to boot. He completed our small kitchen renovation with care and great…
George always kept to commitments and arrived on time. He offered helpful suggestions during his initial visit and promptly provided a reasonably…
Saaid is the best craftsman I have worked with. He knows what he is doing from the very beginning. He has a great knowledge of construction…
FAQ
Frequently Asked Questions about Flat Conversions Balham
What should I budget for a flat conversion in Balham?
Budget the building work first: an England-wide guide gives £40,000 to £80,000 in construction for a straightforward two-flat split (Mayfair Studio, 2026), then add design, planning, building control and utility connection fees. The published London all-in figure is £50,000 to £120,000 (Architectural Drawings, 2026). Check the council's conversion policy for Balham first, because it decides which houses can be split at all.
Can you convert a Balham house into flats?
Only with planning permission, and Wandsworth's policy starts from protecting family housing. Its Local Plan, adopted on 19 July 2023, limits the conversion of single dwellings into flats through policies LP25 and LP26. Your designer or planning agent makes the case against those policies before any building work is priced in detail.
What size must a bedroom be in a new Balham flat?
Under London Plan 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. The London Plan table treats conversions as new dwellings, so these minimums apply to a Balham house split into flats.
What sound insulation do new flats in a converted house need?
Approved Document E sets 43 dB airborne sound insulation for walls, floors and stairs in flats formed by material change of use, and 64 dB maximum impact for floors and stairs. We build the separating floors and walls to that performance and allow for pre-completion testing before the flats are finished.
Can flats in a Balham terrace be turned back into one house?
Yes, physically. The job removes the second kitchen and the lobby partitions, reopens the staircase into the house, and the suppliers merge the meters. Settle the planning position first, because merging flats reduces the number of homes and Wandsworth's Local Plan protects the existing self-contained housing stock. Your designer checks that; we then strip out, rewire, replumb and make good.
Does each new flat in Balham need outdoor space?
Where borough plans set no higher standard, London Plan Policy D6 asks for at least 5 square metres of private outdoor space for 1 to 2 person dwellings, plus 1 square metre for each additional occupant. In a Balham terrace the garden usually goes to the lower flat, so the upper flat's space is a design question.
Do small Balham conversions pay towards affordable housing?
They can. Under Wandsworth Policy LP23, developments of 1 to 9 dwellings (gross) must make a contribution per unit towards affordable housing, subject to indexation, unless at least 15% of units are affordable on site. Your planning agent confirms how it applies to a house split into flats before the budget is fixed.
Who serves party wall notices on a Balham flat conversion?
You do, as building owner, or a party wall surveyor on your behalf. Wandsworth's party walls page says these matters are between adjoining owners and points to the government's explanatory booklet. We provide the method statement and sequence the surveyor needs, and start that work only once the notices are settled.
Does a new flat in a Balham conversion need dual aspect?
London Plan Policy D6 says housing development should maximise dual aspect dwellings and normally avoid single aspect ones. In a terrace split floor by floor, each flat usually runs front to back and gets both. A layout that splits a floor front and rear creates single aspect flats, which weakens the application.
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