Windsor, Berkshire
Single-storey rear extension in Windsor
Single-storey rear extension in Windsor: ground-floor space across the back of the house, usually for a kitchen, dining or family room. We measure the house, show you what the rules allow, price it in writing and build it.
We cover Windsor (SL4) as part of our Berkshire work. A single-storey rear extension in Windsor is mostly built from the garden side, so the house stays usable for most of the job.
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 single-storey rear extension cost in Windsor?
Guide prices for a single-storey rear extension in Windsor start from our South East England rate of £2,130–£3,470 per square metre, including VAT. South East prices run above our West Midlands baseline, mainly on labour rates and clay-soil foundations.
| Size | Guide price inc VAT |
|---|---|
| 3 m wide × 4 m deep (12 m²) | £25,500–£41,500 |
| 4 m wide × 5 m deep (20 m²) | £42,500–£69,500 |
| 4 m wide × 6 m deep (24 m²) | £51,000–£83,500 |
These are guide ranges; the written quote after the survey is the figure that counts.
Do you need planning permission for a single-storey rear extension in Windsor?
Planning for a single-storey rear extension in Windsor follows the English householder rules.
Under England's householder permitted development rules you can usually add 3 metres at the back of an attached house, or 4 metres on a detached house, without a planning application, as long as the extension stays under 4 metres high and its eaves stay under 3 metres where it is within 2 metres of a boundary.
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. At the first visit we measure what is there now and tell you which route fits: permitted development, prior approval or a planning application.
What are homes in Windsor like to extend?
Commuter semis and detached houses make up much of Windsor, and longer gardens make England's prior approval route for deeper rear extensions worth considering.
How a single-storey rear extension in Windsor 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.
Drawings and budget
Floor plans and elevations for the options, each with a guide price.
Approvals
Permitted development check, prior approval or planning application, then Building Regulations drawings and structural calculations, plus party wall notices where they apply.
Fixed price and build
A written price for the agreed design, a start date and a named contact through the build, ending with the building control completion certificate.
Single-storey rear extensions near Windsor
Neighbouring places we cover include Slough (1.8 miles) and Egham (4.1 miles).
- Single-storey rear extension in Slough
- Single-storey rear extension in Egham
- Single-storey rear extension in Burnham
- Single-storey rear extension in Staines
- Single-storey rear extension in Stanwell
Other work in Windsor:
FAQ
Single-storey rear extension questions in Windsor
What postcode areas do you cover around Windsor?
Including SL4, and the surrounding Berkshire area.
How much does a single-storey rear extension cost in Windsor?
As a guide, £2,130–£3,470 per square metre including VAT for a standard specification. For example, 3 m wide × 4 m deep (12 m²): about £25,500–£41,500 at that rate. Your written price follows the survey.
How deep can a single-storey rear extension be without planning?
In England, 3 metres on an attached house and 4 metres on a detached house under permitted development, or up to 6 and 8 metres with prior approval. Wales allows 4 metres; Scotland and Northern Ireland have their own limits.
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 I need planning permission for a rear extension in Windsor?
Often not for a single-storey rear extension of up to 3 metres (4 metres on a detached house) under permitted development, or up to 6 or 8 metres with prior approval, unless the house is in a conservation area or its rights have been removed.
Can you match the brick or stone on my Windsor house?
We source the closest match and show you samples before ordering; reclaimed materials are often the best match on older houses.