Kitchen extensions with bedrooms above in Brentford

Brentford: the key facts for this kind of project.

Postcode districts: TW8
County / area: Greater London, England
Price region: London
Guide price: £67,000–£90,500 (£2,400–£3,240 per m²), kitchen units and worktops priced separately
Approval route: It may be permitted development if it goes no more than 3 m beyond the original rear wall (counting any single-storey part) and stays 7 m from the rear boundary; otherwise it needs planning permission.
Nearest towns: Kew (0.9 miles), Ealing Common (1.5 miles), Isleworth (1.7 miles)
First visit: Free, no obligation

About a kitchen extension with bedrooms above

A kitchen extension with bedrooms above is a two-storey extension designed so the ground floor becomes a larger, usually open-plan kitchen and dining space, with one or two bedrooms or a bathroom on the first floor. It is a natural fit for a two-storey rear extension. The key design issues are the steel beams that open up the house, glazing and ventilation.

We cover postcode district TW8 in and around Brentford, along with neighbouring Kew, Ealing Common and Isleworth.

What it costs in Brentford

Most of the cost of a kitchen extension with bedrooms above is set by its size and specification. For Brentford and the rest of London, our guide is £2,400–£3,240 per m² including VAT, so about £67,000–£90,500 (kitchen units and worktops priced separately) for a 4 m × 3.5 m footprint on two floors (28 m² of new floor space). Keep a contingency of around 10% for things nobody can see until the ground is opened up.

Spec	Per m²	A 4 m × 3.5 m footprint on two floors (28 m² of new floor space)
Essential	£2,210–£2,980 per m²	£62,000–£83,500
Standard	£2,400–£3,240 per m²	£67,000–£90,500
Premium	£2,880–£3,890 per m²	£80,500–£109,000

Planning and building regulations in Brentford

In England, a two-storey rear kitchen extension can be permitted development if it goes no more than 3 m beyond the rear wall of the original house and stays at least 7 m from the rear boundary, with matching materials and roof pitch, outside protected areas. No balconies are allowed. Deeper designs need planning permission, costing £548 (or £575 for applications made from 8 December 2026).

Approval in England: Householder planning application: £548 (or £575 for applications made from 8 December 2026). Lawful development certificate: £274 (about £288 for applications from 8 December 2026). Councils should decide householder applications within 8 weeks of validation.

Building regulations: Building regulations approval (full plans recommended) from the council or a registered building control approver, with a completion certificate at the end.

Design points for Brentford homes

Services and drainage

Sinks, dishwashers and an upstairs bathroom all need waste routes to the drains, often near where the extension goes. We check the drains early and plan soil stacks, gas and electrical supplies so the kitchen layout is not limited later.

Steel beams and the open-plan opening

Removing the old rear wall to make one large room means a steel beam, sometimes several, to carry the first floor and roof. The engineer sizes the steel and its supports, and we decide early whether you want a flush ceiling with the beam hidden or a downstand, as this affects ceiling heights.

How we'd run your project

Start at your house
We come to your home in Brentford, measure up, check the ground floor walls and roof structure, and note anything near the boundaries.
Plans, then approval
Measured survey, design, then the right approval route for your house. We explain each step before we take it.
Detail and price
Construction drawings, engineer's calculations and building control sign-off, then a written fixed price for the build.
Build and hand over
We manage the build from groundworks to decoration-ready finish and hand over with the completion paperwork.

Questions about kitchen extensions with bedrooms above in Brentford

Do I need planning permission for a kitchen extension with bedrooms above in Brentford?

Brentford is in England, so England planning rules apply. It may be permitted development if it goes no more than 3 m beyond the original rear wall (counting any single-storey part) and stays 7 m from the rear boundary; otherwise it needs planning permission. If in doubt, a lawful development certificate or a planning application gives you certainty before you build.

Who handles building regulations for a project in Brentford?

We handle it as part of the project. What's needed in England: building regulations approval (full plans recommended) from the council or a registered building control approver, with a completion certificate at the end. We prepare the drawings and the engineer's calculations, book the inspections and pass you the completion paperwork at the end.

Which postcodes do you cover around Brentford?

We cover Brentford (TW8) and nearby places including Kew, Ealing Common and Isleworth, plus the rest of Greater London. The first site visit is free.

Is it cheaper to build a kitchen extension and bedrooms at the same time?

Yes, in most cases. Building both floors at once means one set of foundations, one roof, one scaffold and one set of approvals. Adding a first floor later means removing the original roof, possibly strengthening the foundations and disrupting the kitchen again. If you think you will need the bedroom, build it now.

Can I keep using my kitchen during the build?

For part of it. The new structure can be built while your existing kitchen stays in use, but when the rear wall is opened and the new kitchen is fitted there will be several weeks without one. We plan when this happens and help you set up a temporary kitchen elsewhere in the house.

Nearby

Nearby towns we cover for kitchen extensions with bedrooms above:

Other extensions in Brentford

All two-storey extension services in Brentford · Kitchen extensions with bedrooms above across Greater London

Ready to talk it through? Call us or send the form and we'll arrange a visit to your home in Brentford.