Kitchen Extensions Westminster

Kitchen extension work in Westminster starts from a small pool of houses: 91% of the City's homes are flats and 9% are houses, and terraced houses make up 8% of the stock. Conservation areas cover over 76% of the City, so a design has to answer Westminster's conservation guidance as well as the permitted development limits. That shapes the size of what you can build, how it looks from the garden, and which consents come before the first dig.

In Westminster, a rear kitchen extension of about 30 square metres typically costs £45,000 to £97,500 excluding VAT, or £60,000 to £100,000 for a side return (indicative London ranges, Resi, MyBuilder and Checkatrade, 2026). GS Renovation Ltd, a building contractor based in Potters Bar, does the work in Westminster: the structural engineer we appoint designs the foundations and steel, we build the room and fit the kitchen, and a registered electrician certifies the electrics.

Which Westminster homes can take a kitchen extension

A house can have permitted development rights for a kitchen extension; a flat has none, so any extension to a flat needs planning permission. Householder permitted development rules for extensions apply to houses only, not to flats and maisonettes, so a ground floor or garden flat owner starts with an application rather than a set of allowances. With flats making up 91% of Westminster homes, that is the first question we ask on a survey, before any talk of glazing or worktops.

For a terraced house the usual options are a single-storey rear addition or an infill beside the closet wing. For a garden flat an extension can still be possible, but the lease will normally require the landlord's licence to alter as well as planning permission, and the structure touches a building other people own. On a terrace the new foundations and walls can sit on or near the party wall. Where they do, the Party Wall etc. Act applies and the building owner serves notice on the neighbours. We programme the two cases differently, because their approvals run on separate clocks.

Housing in Westminster

Westminster has around 132,230 homes on the Council Tax list: 40% post-war, 10% interwar and 48% predate 1919, with 91% flats and 9% houses. Where most homes are flats, only a ground floor flat in Westminster with its own garden can extend its kitchen.

What conservation area guidance does to the extension's size

In a conservation area the extension has to stay smaller than the house and read as an addition to it. Westminster's guidance on development in conservation areas says extensions should respect the scale and proportions of the existing building and must be architecturally subordinate to the main building. On a stucco or brick terrace that tends to mean a lower parapet, a set back from the flank wall, and materials that sit quietly behind the original.

The same guidance says full width rear extensions are generally not acceptable, except in certain circumstances at basement level. So a glass box across the whole back of the house is a hard sell here. A part width addition with a roof light over the dining end can give the kitchen the light it needs while keeping to the guidance. The steel that carries the opening into the house is sized by the structural engineer we appoint, and we build it and the drainage around that footprint.

Side infills, basements and the permitted development limits

A side infill needs planning permission on designated land, and a basement kitchen needs it anywhere in Westminster. Under permitted development rules, all side extensions on Article 2(3) designated land, such as a conservation area, require householder planning permission. With conservation areas covering over 76% of the City, check the conservation area map before a side return infill is drawn, because inside one it goes to an application rather than being built as of right. The larger rear extension allowed through prior approval is barred on that land too.

Taking the kitchen down into a new basement is also controlled. Westminster's city-wide Basement Development Article 4 Direction came into force on 31 July 2016 and removes permitted development rights for basement development throughout the city. That means an application even where the extension above ground would not need one, backed by a structural methodology statement and an engineer's self-certification. It also changes the build sequence, since underpinning, waterproofing and the drainage pump all come before any kitchen joinery goes in.

Running the build on a tight Westminster street

A kitchen extension here is built from the street, so access and hours shape the programme. Westminster needs a temporary structure licence to put scaffolding, construction fencing or similar apparatus in the road or on the pavement, and its building site guidance says the footway must not be reduced to less than 1.5m wide around works. On a narrow terrace that decides where the skip, the mixer and the steel delivery can go.

Westminster's normal hours for noisy construction are Monday to Friday 8am to 6pm and Saturday 8am to 1pm. For anything noisy outside those hours, Westminster asks for a Control of Pollution Act Section 61 application at least 28 days before work starts. We plan breaking out, steel lifts and concrete pours inside the normal window, then run the kitchen fit-out in the same programme once the shell is dry and watertight, so the fitters are not waiting on a second contractor.

• Airbrick ducts to keep existing timber floors ventilated
• Boiler relocation and flue changes on the enclosed rear wall
• Sliding, bifold and steel-framed glazed doors to the garden

VOA Council Tax stock of properties, March 2025, for all 24 statistical areas in Westminster. Counts rounded by the VOA.

For the wider picture around kitchen extensions in Westminster, see kitchen renovation in Westminster, our Westminster area guide, fitting the kitchen itself, how building control inspects an extension, how we handle kitchen extensions across London and Renovating a 1930s Semi.

Why Choose GS Renovation in Westminster

We take a Westminster kitchen extension from the approved drawings to a working kitchen as one job. The structural engineer we appoint sizes the steel, a registered electrician certifies the wiring, and we coordinate the drainage, roof lights, glazing and kitchen fit-out in a single programme. You get one written programme showing where the street licence, the building control start notice and each trade fall, so you know what happens on each day of the build.

• Rooflights set out against the engineer's steel layout
• Screed left to dry before the kitchen floor finish goes down
• Our own trades on site rather than a chain of subcontractors

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.