Osterley, Greater London
Semi-detached rear extension in Osterley
Semi-detached rear extension in Osterley: single or two-storey extensions for semi-detached houses, with side access and one party wall. We measure the house, show you what the rules allow, price it in writing and build it.
Osterley is covered from our Greater London round, including TW3, TW5 and TW7. Where an Osterley semi already has a small lean-to at the back, we usually replace it rather than extend it.
Book a free site visit
Tell us about the house and we'll call to arrange a free, no-obligation visit.
How much does a semi-detached rear extension cost in Osterley?
In Osterley, our guide for a semi-detached rear extension is £2,470–£4,030 per square metre including VAT for a standard specification. London prices sit at the top of our range because of labour rates, access through the house, parking suspensions and skip licences.
| Size | Guide price inc VAT |
|---|---|
| 3 m wide × 4 m deep (12 m²) | £29,500–£48,500 |
| 4 m wide × 5 m deep (20 m²) | £49,500–£80,500 |
| 4 m wide × 6 m deep (24 m²) | £59,500–£96,500 |
Your written price follows a measured survey and an agreed design, so it reflects your house, not an average.
Do you need planning permission for a semi-detached rear extension in Osterley?
Here is how the rules in England apply to a semi-detached rear extension in Osterley.
In England a single-storey rear extension can often be built under permitted development: up to 3 metres beyond the original rear wall of an attached house, or 4 metres on a detached house, no higher than 4 metres, with eaves no higher than 3 metres if any part is within 2 metres of a boundary.
England's rules allow a rear extension of more than one storey without an application only when it is no deeper than 3 metres and at least 7 metres from the boundary opposite the rear wall, and never on designated land. Most two-storey schemes need householder planning permission.
England also has the larger home extension route: a single-storey rear extension of up to 6 metres on an attached house or 8 metres on a detached house, after prior approval from the council. The council notifies your neighbours and has 42 days to decide; the fee is £249 (£310 for applications made from 8 December 2026). The route is not available on designated land such as conservation areas.
Conservation areas, National Parks, National Landscapes and the Broads restrict permitted development, and listed buildings always need listed building consent. Before any drawing we look up the property's history with the council, because earlier extensions and removed rights change the answer.
What are homes in Osterley like to extend?
Much of Osterley is 1920s and 1930s semis and short terraces with longer gardens than inner London, which suit full-width single-storey rear extensions. Parking suspensions, skip licences and controlled hours on residential streets shape the programme more than the build itself.
How a semi-detached rear extension in Osterley comes together
Look round and measure
A free visit to see the back of the house, measure it, check the drains and boundaries and hear what you need.
Options and costs
We draw layout options and price each one, so the budget shapes the design rather than surprising you later.
Approvals
Permitted development check, prior approval or planning application, then Building Regulations drawings and structural calculations, plus party wall notices where they apply.
Written price, then build
Once the design and approvals are in place, you get a fixed written price and programme, and we build through to sign-off.
Semi-detached rear extensions near Osterley
Neighbouring places we cover include Isleworth (0.6 miles) and Hounslow (0.9 miles).
- Semi-detached rear extension in Isleworth
- Semi-detached rear extension in Hounslow
- Semi-detached rear extension in Heston
- Semi-detached rear extension in Brentford
- Semi-detached rear extension in Southall
Other work in Osterley:
FAQ
Semi-detached rear extension questions in Osterley
Can you match the brick or stone on my Osterley house?
We source the closest match and show you samples before ordering; reclaimed materials are often the best match on older houses.
Who will build my extension?
Vetted building teams working under contract to us. Your contract is with S&K Property Investments and Improvement Ltd for the design and the build.
What if my neighbour has already extended?
That can make a matching depth easier to justify. We measure theirs at the survey.
Will I need a structural engineer?
Yes for the beam over the new opening and usually the foundations; we arrange them and their calculations go to building control.
Do you handle building control in Osterley?
Yes. We apply to the council or a registered building control approver and hand over the completion certificate.
How long does a rear extension take to build in Osterley?
Most single-storey rear extensions take 10 to 16 weeks on site and two-storey extensions 16 to 26 weeks, after design and approvals.