Kitchen Extensions St John's Wood

A kitchen extension in St John's Wood is a job for the minority of owners who have a house and a garden. The VOA list puts 90% of homes here as flats and 10% as houses, split evenly between terraces and semi-detached or detached villas. Householder permitted development applies to houses only, so a ground floor flat owner starts from a planning application. Where the house sits inside the St John's Wood Conservation Area, first designated in 1967, that designation shapes how far back and how wide the new kitchen can go.

In St John's Wood, 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 St John's Wood: 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 St John's Wood homes can extend the kitchen at all

Houses can, flats need planning permission for any extension. In St John's Wood 5% of homes are terraced houses and 5% are semi-detached or detached, and those are the owners with householder permitted development rights to lean on. The national rules for extensions apply to houses only and not to flats and maisonettes. If you own the garden flat in a converted villa, the kitchen extension goes through a full planning application, and the freeholder's consent under your lease normally comes into it too.

For a house, the practical question is which wall the kitchen grows from. Where a terrace has a rear addition with a narrow return beside it, the new kitchen can fill that return and open the back room into it. Footings near the neighbour's wall and steel bearing into a party wall are notifiable under the Party Wall etc. Act, and the building owner serves those notices. A detached villa has more room at the side and rear, but side extensions bring their own planning route, covered below. The shape of the extension decides where the steel and drainage go, so we price from the drawings.

Housing in St John's Wood

On the valuation list St John's Wood counts about 8,840 homes, 90% flats and 10% houses; 23% predate 1919, 31% are interwar and 46% post-war. Most homes here are flats, and only a ground floor flat in St John's Wood with its own garden can extend its kitchen.

How the conservation area limits rear and side extensions in St John's Wood

Inside the conservation area, it removes the side extension route and narrows the rear one. The St John's Wood Conservation Area was designated in 1967 and extended in 1979 and 2007, and a conservation area is Article 2(3) designated land. On that land all side extensions need householder planning permission, and the larger rear extensions that go through prior approval are not available. That leaves a rear extension of up to three metres on a terrace or semi and four metres on a detached house as the permitted route, subject to the other conditions and where the house has not lost those rights. Westminster has also removed some rights in eight of its conservation areas, and a house on the statutory list needs heritage consent for an extension as well.

Westminster's conservation area guidance adds the design test. Extensions should respect the scale and proportions of the existing building and stay architecturally subordinate to it, and full width rear extensions are generally not acceptable except in certain circumstances at basement level. For a St John's Wood villa, that points to a kitchen extension that keeps back from one side, sits lower than the main eaves and uses brick and openings that read as secondary to the house.

Height, glazing and roof lights on a St John's Wood kitchen extension

Keep the single storey low and let the roof glazing do the work. Under permitted development a single-storey rear extension cannot exceed four metres in height, and in a conservation area a lower, quieter roof line is also what the subordinate test asks for. A flat roof with a large roof light over the kitchen worktop usually gives more daylight than a tall glazed gable, and it keeps the extension below the sills of the rooms above.

Glazing is where a St John's Wood kitchen extension meets the building regulations for heat loss, so the area of glass, the roof light specification and the insulation in the flat roof are settled together at drawing stage. Sliding or bifold doors to the garden sit on a steel or a lintel sized by the structural engineer we appoint. We order the glazing early, because long lead times on large doors can hold up the kitchen fit-out behind them.

Building control, drainage and the kitchen fit-out in St John's Wood

Westminster runs its own building control service, and where you use it rather than a registered building control approver, an extension goes in as full plans. The District Surveyors Building Control Service accepts building notices only where the work does not affect the layout, and an extension does. On a full plans application it aims to contact you within 5 weeks with a decision, though it says this may take longer, so we build that wait into the programme. Westminster must then be told the start date at least 2 days before work begins.

Underground drainage is usually the first job on site in St John's Wood, because the kitchen sink and any new gully move out to the new rear wall. Where a public sewer runs under the extension, the sewer owner's agreement and the drainage plan settle how it is protected before the foundations are dug. We then run the shell, the steel into the house and the kitchen fit-out as one programme, so the worktops are templated once the walls are plastered, not months later by a separate firm.

• Soil stack and gully rerouting beneath the new floor
• Party wall process explained, with drawings for your notices
• Floor levels matched through the old opening

VOA Council Tax stock of properties, March 2025, for St John's Wood North and St John's Wood South. Counts rounded by the VOA.

For the wider picture around kitchen extensions in St John's Wood, see kitchen renovation in St John's Wood, kitchen extensions across Westminster, a side return kitchen infill, the Party Wall Act on a boundary build, our London kitchen extensions page and Kitchen-Diner Layout Ideas.

Why Choose GS Renovation in St John's Wood

We run a kitchen extension as one job, from the drainage and footings through the steel, the roof and glazing to the finished kitchen. You get a written programme that shows the building control stages and where the structural engineer we appoint inspects the steel and foundations. We build to the planning drawings your designer prepares and keep the same site lead on the job from start to handover. On a villa in a conservation street we keep materials and detailing to the approved drawings rather than improvising on site.

• Old kitchen kept in use until the new shell is weathertight
• Itemised pricing, so you can see what every stage costs
• Screed left to dry before the kitchen floor finish goes down

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.