Two-storey extensions for detached houses in Feltham

The basics for Feltham at a glance.

Postcode districts: TW14
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: Hanworth (1.6 miles), Cranford (2.1 miles), Ashford (Surrey) (2.1 miles)
First visit: Free, no obligation

About a two-storey extension for a detached house

This service suits you if you own a detached house and want a substantial amount of extra space, whether a side extension over a drive, a rear extension into the garden or a wraparound. You get a survey of the whole plot, options that compare layouts and costs, the approvals your nation needs, structural design and the build, carried out by vetted teams working under S&K.

We cover postcode district TW14 in and around Feltham, along with neighbouring Hanworth, Cranford and Ashford (Surrey).

What it costs in Feltham

Our guide for London is £2,460–£3,300 per m² including VAT. On a project with a 3 m × 7 m footprint on two floors (42 m² of new floor space), that puts a two-storey extension for a detached house in Feltham at roughly £103,500–£138,500. 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 Feltham

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 Feltham homes

Keeping it subordinate

Large detached houses can take a large extension, but councils still expect it to look secondary to the main house. A lower ridge, a modest set-back at the front and matching materials keep the proportions right, even on a wide plot.

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.

How we'd run your project

Start at your house
We come to your home in Feltham, measure up, check the ground floor walls and roof structure, and note anything near the boundaries.
Choose the approval route
Some designs fit permitted development, most need a householder application. We decide which applies in England before drawing in detail.
Price it properly
Once the engineer's calculations are in, we fix the build price in writing, with a clear list of what's included.
Build
Foundations, walls, floor, roof, windows, then first and second fix. We break through into the house as late as we can.

Questions about two-storey extensions for detached houses in Feltham

Which postcodes do you cover around Feltham?

We cover Feltham (TW14) and nearby places including Hanworth, Cranford and Ashford (Surrey), plus the rest of Greater London. The first site visit is free.

How long does a two-storey extension for a detached house take?

Allow 4 to 8 weeks for survey and design, then the approval period (councils should decide householder applications within 8 weeks of validation), then 4 to 8 weeks of technical design, which can overlap. The build itself usually takes 14 to 20 weeks, longer for large or complex designs.

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

Our guide for London, which covers Feltham, 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.

How big an extension can a detached house take?

It depends on the plot, the boundaries and local design policy rather than a fixed limit. Under permitted development in England, extensions must not cover more than 50% of the land around the original house. With planning permission, the council judges size on proportion, neighbours and the character of the area.

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.

Nearby

Close to Feltham? We work across the area, including:

Other extensions in Feltham

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

Book a free site visit in Feltham and we'll tell you what's possible, what approvals you need and what the design stage would cost.