Flat Conversions Old Street

Flat conversion in Old Street is a narrow service, and it is worth being plain about it: 99% of homes here are already flats and 1% are houses, so splitting a house is rare. The conversion work that does arise is a large terrace divided under Islington's Policy H2, a shop or other ground floor unit turned into a home where planning allows, or two flats joined back into one. Each needs planning permission or prior approval before the build starts.

In Old Street, 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 Old Street: 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.

Why house-to-flat conversions are rare in Old Street

Splitting a house into flats is the classic conversion, and in Old Street it is rare, because the valuation list records 99% of homes as flats and 1% as houses, all of them terraced. Where one of those terraces is large enough, Islington's Local Plan Policy H2 only permits converting it into more self-contained units if the existing dwelling's total floor area exceeds 125sqm GIA. Planning permission is required whenever a building is converted into smaller units such as self-contained flats, so the measured survey and the owner's planning advice come before any layout is priced.

The mix of flats is fixed by the same policy. Under Policy H2 a conversion must contain no studio or bedsit units and no more than one one-bedroom unit, which in a terrace points towards two larger flats, such as a maisonette over a garden flat. The stair, the entrances and the service routes are planned first and the rooms fitted around them, because an existing house rarely divides evenly floor by floor. In an Old Street terrace the shared hall becomes a protected escape route, so meters and storage have to be placed with that in mind.

Housing in Old Street

Old Street has about 6,800 homes on the Council Tax list: 16% pre-1919, 5% interwar and 76% post-war, with flats making up 99% and houses 1%. Where most homes are flats, changing the number of flats in Old Street needs the freeholder and usually planning.

Space standards every new Old Street flat must meet

Each flat created in Old Street has to meet the minimum space standards, because Islington's Local Plan says all new residential development, including conversions and changes of use, must meet them. The London Plan table confirms that a new dwelling includes conversions and change of use. Under Policy D6 a single bedroom must be at least 7.5 square metres and 2.15m wide, and a double or twin bedroom at least 11.5 square metres. GOV.UK says the Nationally Described Space Standard sits solely within the planning system, so these sizes are settled at the drawing stage and cannot be traded away on site.

Height and aspect are where older buildings fall short. 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, and asks for dual aspect flats to be maximised and single aspect ones normally avoided. Where the borough sets no higher standard it asks for at least 5 square metres of private outdoor space for 1 to 2 people, plus 1 square metre for each additional occupant. In an Old Street terrace the height rule tends to decide whether a low top storey can stand as a flat of its own.

Sound, fire and services between the new Old Street flats

A material change of use from one house into flats brings Part E and Part B into force for the walls and floors between the new units. Approved Document E sets lower sound insulation 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. Over old timber joists in an Old Street terrace that means independent ceilings, resilient bars, mineral wool and a floating floor, followed by pre-completion sound testing before the flats are signed off.

Fire separation runs alongside. Each flat becomes its own compartment, the shared hall and stair become a protected escape route, and every pipe and cable passing between units is fire stopped. Because the converted building will have common areas, Islington's building notice route is closed to it, so the work is approved on full plans or by a registered building control approver. The council must process full plans within five weeks, or two months if agreed. Part L applies to the new units and Part M to any new entrances. Separate services come early on site: a meter, consumer unit and water supply for each flat, with new postal addresses arranged through street naming and numbering.

Shops into homes, party walls and reversing a conversion in Old Street

On Old Street itself a conversion may start with a shop rather than a house. Class MA permits a change of use from Class E to Class C3, with prior approval covering adequate natural light in all habitable rooms. Islington's Article 4 Directions withdraw it across the CAZ and the Kings Cross CAZ Fringe, where full planning permission is needed instead. Islington Policy DH7 says shops converted to residential use, including through permitted development, must retain the shopfront fenestration and natural surveillance of the street. So the new home keeps its large glazed front, and we plan privacy with internal screens, a raised floor or a set back bedroom.

Neighbours come into it wherever a party wall is cut into for new floors or steels. Islington's building control FAQ says that if the Party Wall Act 1996 applies you must notify your neighbours at least six weeks before you start, and the council is not involved in any Party Wall Agreement; the building owner serves the notices. The reverse job needs consent too: Islington's Local Plan says converting two or more units into a single dwelling is material and requires planning permission. Once that is granted we remove the second kitchen and rework the separation for an Old Street home.

• A kitchen and shower room fitted in every new flat
• Separating floors with independent ceilings and acoustic insulation
• Steel beams and new openings built to the engineer's design

VOA Council Tax stock of properties, March 2025, for Old Street & St Luke's. Counts rounded by the VOA.

Plenty of Old Street projects start with one job and grow, so it helps to see structural alterations in Old Street, flat conversions across Islington, builders in Islington, refurbishing a flat that has already been converted, how we handle flat conversions across London and Renovation Budget & Contingency.

Why Choose GS Renovation in Old Street

A flat conversion in Old Street is decided by drawings and consents long before the build, so we come in once the scheme is drawn. We visit, check the measured survey against the room sizes and the separation details, and give a written quotation with a programme that puts fire and sound separation first. The structural engineer we appoint details any new openings, a registered electrician certifies the electrics, a registered gas engineer does the gas work, and the handover pack includes the sound test results the owner needs for building control.

• Fire strategy for the stair and each flat entrance settled before strip-out
• Each flat numbered and supplied before the keys are handed over
• Itemised pricing, so you can see what every stage costs

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.