Two-storey extensions for detached houses in Kensal Green

What we'd confirm first for a project in Kensal Green.

Postcode districts: W10
County / area: Greater London, England
Price region: London
Guide price: £103,500–£138,500 (£2,460–£3,300 per m²)
Approval route: Depends on position: a two-storey rear extension may be permitted development (3 m deep, 7 m from the rear boundary); a two-storey side extension needs planning permission.
Nearest towns: Willesden (0.4 miles), Queen's Park (0.7 miles), Harlesden (1.2 miles)
First visit: Free, no obligation

About a two-storey extension for a detached house

A two-storey extension for a detached house is a two-floor addition to the side, rear or both of a house that stands on its own plot. Detached houses often have room on more than one side, so there is more choice of layout and fewer shared-wall issues. The design still needs to respect boundaries, neighbours' windows and the look of the house.

We cover Kensal Green (W10) and the places around it, including Willesden (0.4 miles), Queen's Park (0.7 miles) and Harlesden.

What it costs in Kensal Green

A guide price for Kensal Green: around £103,500–£138,500 for a 3 m × 7 m footprint on two floors (42 m² of new floor space). That works out at £2,460–£3,300 per m² of new floor space, including VAT at 20%. Professional fees for drawings and the structural engineer are listed separately on our prices page.

Spec	Per m²	A 3 m × 7 m footprint on two floors (42 m² of new floor space)
Essential	£2,260–£3,040 per m²	£95,000–£127,500
Standard	£2,460–£3,300 per m²	£103,500–£138,500
Premium	£2,950–£3,960 per m²	£124,000–£166,500

Planning and building regulations in Kensal Green

In England, a two-storey rear extension on a detached house can be permitted development within 3 m of the original rear wall and at least 7 m from the rear boundary, with matching roof pitch and materials, outside protected areas. Any two-storey side or wraparound extension needs planning permission, costing £548 (or £575 for applications made from 8 December 2026), with a decision due within 8 weeks of validation.

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 Kensal Green homes

Choosing the best side

On a detached house you can often extend on either side or the rear. We look at orientation for daylight, where the stairs and landing are, the distance to each boundary, drains and trees, so the extension goes where it adds the most useful space.

Larger spans and steelwork

Bigger extensions often mean wider openings and longer spans, which need more steel and sometimes a steel frame. The engineer designs these early, because the size of the steel affects ceiling heights, floor depths and the cost.

How we'd run your project

Look at the house
We start in Kensal Green with a free visit: measurements, photos, a look at the loft and drains, and a frank chat about budget.
Get it approved
Once you're happy with the design we submit it to the council for Kensal Green and deal with any questions from the planning officer.
Engineer it
Foundations sized for two floors, steels for any openings, and building control approval, all before anyone starts on site.
Build it
The new structure goes up first, then we open into the house, finish inside and get the completion certificate.

Questions about two-storey extensions for detached houses in Kensal Green

Who handles building regulations for a project in Kensal Green?

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 Kensal Green?

We cover Kensal Green (W10) and nearby places including Willesden, Queen's Park and Harlesden, plus the rest of Greater London. The first site visit is free.

How much does a two-storey extension for a detached house cost in Kensal Green?

Our guide for London, which covers Kensal Green, is £2,460–£3,300 per m² including VAT. A typical project with a 3 m × 7 m footprint on two floors (42 m² of new floor space) comes to about £103,500–£138,500. Design and approval fees are extra, and we fix the build price in writing once the design is agreed.

Is a detached house extension a better investment than moving?

It often costs less than the gap between your house and a larger one nearby, once property tax, legal fees and removal costs are counted, but that depends on your area. Extending also has limits: every street has a ceiling price. We give you build costs so you can compare them with local asking prices.

Can I extend a detached house on both sides?

Sometimes. With planning permission, a council may accept extensions on both sides if the house stays well proportioned and keeps gaps to the boundaries. It is more common to extend on one side and the rear, or with a wraparound. We look at the plot as a whole before suggesting more than one extension.

Nearby

Close to Kensal Green? We work across the area, including:

Other extensions in Kensal Green

All two-storey extension services in Kensal Green · Two-storey extensions for detached houses across Greater London

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