Two-storey extensions for semi-detached houses in Greenford

Useful details for planning a two-storey extension for a semi-detached house in Greenford.

Postcode districts: UB6
County / area: Greater London, England
Price region: London
Guide price: £67,000–£90,500 (£2,400–£3,240 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: Northolt (1.5 miles), Southall (1.5 miles), West Ealing (1.7 miles)
First visit: Free, no obligation

About a two-storey extension for a semi-detached house

This service suits you if you own a semi-detached house and want to add bedrooms and living space without moving. On a semi, the main questions are which side to build on and how to treat the attached neighbour. You get a survey, design options, the approvals your nation needs and the build, carried out by vetted teams working under S&K.

We cover postcode district UB6 in and around Greenford, along with neighbouring Northolt, Southall and West Ealing.

What it costs in Greenford

In London, which includes Greenford, we'd expect a two-storey extension for a semi-detached house to cost around £67,000–£90,500 for a 4 m × 3.5 m footprint on two floors (28 m² of new floor space), or £2,400–£3,240 per m² including VAT. Kitchens, bathroom fittings and flooring are priced separately so you can compare like with like.

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 Greenford

In England, a two-storey rear extension on a semi can be permitted development if it goes no more than 3 m beyond the original rear wall and stays 7 m from the rear boundary, with matching materials and roof pitch. A two-storey side or wraparound extension always needs planning permission, costing £548 (or £575 for applications made from 8 December 2026). Protected areas such as conservation areas exclude two-storey rear permitted development.

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 Greenford homes

Keeping the pair balanced

Semis are designed as matching pairs, and a side extension changes that balance. Setting the side extension back from the front wall and keeping its ridge lower helps the pair still read as a pair, which councils' design guides commonly ask for.

The attached neighbour's light

A two-storey rear extension next to the party wall can take light from the neighbour's rear windows. Councils often use a 45-degree test, so the first floor may need to be shorter than the ground floor or set in from the shared boundary.

How we'd run your project

Measure and listen
A visit to Greenford to understand how you live in the house now and what the extra rooms need to do, plus a first look at the structure.
Get it approved
Once you're happy with the design we submit it to the council for Greenford 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.
On site
One project lead runs the job, keeps you updated and arranges inspections at each stage until completion.

Questions about two-storey extensions for semi-detached houses in Greenford

Which postcodes do you cover around Greenford?

We cover Greenford (UB6) and nearby places including Northolt, Southall and West Ealing, plus the rest of Greater London. The first site visit is free.

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

Our guide for London, which covers Greenford, is £2,400–£3,240 per m² including VAT. A typical project with a 4 m × 3.5 m footprint on two floors (28 m² of new floor space) comes to about £67,000–£90,500. Design and approval fees are extra, and we fix the build price in writing once the design is agreed.

How long does a two-storey extension for a semi-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.

Will a side extension make my semi look like a terrace?

It can if it fills the whole gap to the boundary at first floor and the neighbour does the same. Many councils ask for a first-floor gap to the side boundary or a set-back for this reason. We design the extension to keep the semi reading as one of a pair.

What if my neighbour has already extended?

That often helps. An existing extension next door can reduce the effect of yours on their light, and may show what the council accepts on your street. It can also mean building alongside their wall, so we check its position, foundations and any windows facing your plot at the survey.

Nearby

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

Other extensions in Greenford

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

The quickest next step is a visit. We'll look at your house in Greenford and give you an honest view of the options.