Flat Conversions in London

A flat conversion in London usually means one of three jobs. Splitting a Victorian or Edwardian house into two or more self-contained flats. Turning a shop, office or the floors above a shop into flats. Or stripping out an existing flat, often in an older conversion, and redoing it properly.

The building work for the first two is mostly about separating things that used to be shared: floors, stairs, pipes, cables and meters. The third is mostly about what the last people did and how much of it can stay.

There’s a longer guide to the planning side and the costs of splitting a house in converting a house into flats in London. This page is more about the work itself.

Planning first

Splitting one house into flats needs planning permission almost everywhere in London, and several boroughs resist losing family houses. Many have policies on minimum flat sizes, which usually follow the national space standard: around 37 m² for a one-person studio with a shower room, 50 m² for a one-bed, two-person flat.

Commercial buildings can sometimes go through a permitted development route instead, Class MA, which was introduced in 2021. It needs prior approval rather than a full application, but the conditions have changed more than once since then and many London boroughs have Article 4 directions that remove it in parts of the borough, so check the current version before buying anything on the strength of it.

Building regulations for a change of use

Once a house becomes flats, the regulations treat it as a material change of use. That brings in a whole list of requirements at once:

“Where there is a material change of use of the whole of a building, such work, if any, shall be carried out as is necessary to ensure that the building complies with the applicable requirements of the following paragraphs of Schedule 1—”

Building Regulations 2010, regulation 6(1)

The list that follows runs from fire escape and fire spread through ventilation, hot water, bathrooms, kitchens, drainage, heating appliances, insulation and electrics. In practice that means the old house has to be brought up to a standard close to new build in most of the things that matter for safety and comfort, even where you weren’t planning to touch them.

Fire separation is the biggest item. Each flat has to be its own fire compartment, so the floors between flats and the walls to the common stair need fire resistance, usually 60 minutes. In a small conversion of a house of no more than three storeys, building control can accept less on the floors. The common stair needs fire doors to each flat and a fire alarm system linked through the building.

Sound

Noise between flats causes more complaints after a conversion than anything else. The requirement is short:

“Dwelling-houses, flats and rooms for residential purposes shall be designed and constructed in such a way that they provide reasonable resistance to sound from other parts of the same building and from adjoining buildings.”

Building Regulations 2010, Schedule 1, Part E1

An original Victorian floor is pine boards on joists with a lath and plaster ceiling below. It does almost nothing for sound. A conversion floor typically gets mineral wool between the joists, a new ceiling of two layers of acoustic plasterboard on resilient bars or hangers, and sometimes an extra layer on top as well.

Conversions have to be sound tested before completion. A tester comes in, plays noise in one flat and measures it in the next. If the floor fails, the fix is usually expensive, because it means taking ceilings down in a finished flat. The details have to be right first time.

Layout helps too. Kitchens over kitchens and bedrooms over bedrooms make the numbers easier. A living room over someone’s bedroom is the arrangement that leads to complaints.

Splitting the services

Each flat needs its own electricity supply and meter, which in most of London means applying to UK Power Networks. Lead times for new supplies can run to several months, and it’s one of the most common reasons conversions finish late. Each flat also needs its own gas meter if it has gas, or an electric heating system if not.

Water is with Thames Water in most of London, Affinity Water in parts of the north-west. New supplies and any new connection to the public sewer need applications. A Victorian house usually has one old lead or iron supply pipe and drains laid in the 1890s, which often need replacing at the same time.

Inside, the soil stacks, plumbing and electrics are usually stripped back and redone. Pipes running from one flat through another cause trouble later with access and with the fire separation, so they’re rerouted into the flat they serve where possible.

The new flats will also need addresses. In London, street naming and numbering is handled by the council under the London Building Acts (Amendment) Act 1939, and the utility companies generally want an official address before they’ll connect a supply.

Older conversions

A lot of London’s converted houses were split in the 1960s, 70s and 80s, sometimes with little or no building control involvement. Buying or refurbishing a flat in one of them often turns up hollow-core doors on the stair, no fire stopping between floors and shared pipework.

The law has a category for these buildings:

“This section applies to a converted block of flats if— (a) building work undertaken in connection with the conversion did not comply with the appropriate building standards and still does not comply with them; and (b) less than two-thirds of the self-contained flats are owner-occupied.”

Housing Act 2004, section 257(2)

A building like that can count as a house in multiple occupation, and in boroughs with additional licensing the landlord may need a licence. The “appropriate building standards” for older conversions are set by reference to the Building Regulations 1991 as they stood on 1 June 1992, so a conversion done before then to a lower standard still falls short today.

Refurbishing an existing flat

Work inside a leasehold flat is controlled by the lease as much as by the council. Most leases need the freeholder’s consent, a licence for alterations, for anything structural, for moving a kitchen or bathroom, and often for replacing carpet with hard flooring. Mansion blocks and managed buildings usually set working hours, and some ban noisy work on Saturdays.

Removing an internal wall in a flat is often more complicated than in a house, because the wall may be carrying the floor above, which belongs to someone else. There’s more about full refurbishments of existing flats on the apartment renovation page.

The word “flat” itself came from Scotland, where it meant a floor or storey of a building. “Maisonette” is French for a small house, and in London it means a flat on two floors with its own front door.

Force Builders carries out house-to-flat conversions, commercial-to-residential conversions and flat refurbishments across London, mainly in West and Central London.

Frequently Asked Questions – Apartment Refurbishment in London

1. How long does a full apartment refurbishment usually take?

A light refurbishment is often 4 to 6 weeks. A full strip-out with new layout, rewiring, plumbing and decoration is usually 10 to 16 weeks, plus time for the freeholder’s licence beforehand.

2. Do I need planning permission for apartment renovations in London?

Internal work in a flat usually doesn’t need planning permission, but building regulations still apply to structural, electrical and drainage work. Listed buildings need listed building consent even for internal changes, and the lease usually needs the freeholder’s consent.

3. How much does an apartment refurbishment cost?

As a rough guide, a standard full refurbishment in London is often around £800 to £1,200 per m², and higher-spec work can go over £1,800 per m². Kitchens, bathrooms and joinery make up most of the difference.

4. Can I live in my apartment during the refurbishment?

For small jobs, often yes. When the water and power are off for rewiring and replumbing, most people move out for a few weeks.

5. Do you work with apartments in older or listed buildings?

Yes. Period flats often have lath and plaster ceilings, old lead pipework and shared services, and listed ones need consent before original features are changed.

6. What areas of London do you cover?

Anywhere within the M25. Most of the work is in West and Central London, including Kensington and Chelsea, Westminster, and Hammersmith and Fulham.

7. Why choose Force Builders Ltd for your apartment refurbishment?

Force Builders does the building work itself, including structure, plumbing, electrics and finishes, and deals with building control and the freeholder’s paperwork as part of the job.