What is a single-storey extension?
A single-storey extension is a ground-floor addition, usually at the rear of a house, that enlarges a kitchen, living or dining space. Most are built with cavity walls on concrete foundations and finished with a flat roof and roof lantern or a pitched tiled roof.
How much does a single-storey extension cost in Berkshire?
In Berkshire, a single-storey extension typically costs £2,200–£3,250 per m² of floor area, including VAT at 20% (standard rate). For a typical 20 m² project that is roughly £44,000–£65,000. Building costs in the South East run about 12% above the UK average, and the figures for Berkshire are adjusted to reflect that. Design, structural calculations and council fees are extra.
| Size or type | Guide range |
|---|---|
| Smaller project (14 m²) | £31,000–£45,500 |
| Typical project (20 m²) | £44,000–£65,000 |
| Larger project (28 m²) | £61,500–£91,000 |
| Rate per m² | £2,200–£3,250 |
Your quote will depend mainly on:
- Ground conditions and foundation depth
- Roof type and the size of any lantern or roof windows
- Glazing: sliding and bifold doors cost more than French doors
- Kitchen, flooring and finishes, which we can include or leave to you
A guide range is only a starting point: the guide price tool gives an instant figure for your size, and a free survey turns it into a fixed quote.
Do you need planning permission for a single-storey extension in Berkshire?
Before anything is built in Berkshire, we confirm which approvals apply in England. In England a single-storey rear extension is often permitted development: broadly up to 3 metres deep on a semi-detached or terraced house and 4 metres on a detached house, no higher than 4 metres, with eaves no higher than 3 metres within 2 metres of a boundary, and covering no more than half the garden. The larger home extension scheme allows up to 6 or 8 metres if you notify the council first and neighbours have a chance to comment. In conservation areas, National Parks and National Landscapes the larger home extension route, side extensions and cladding are not permitted development. Flats and houses whose rights have been removed need a planning application, and listed buildings need listed building consent.
Building regulations approval comes from the council’s building control service or a registered building control approver. The work is inspected at key stages, such as foundations, drainage and insulation, and a completion certificate is issued at the end.
If the answer is not clear-cut, we can apply for formal confirmation before you commit to the build.
What we handle
On a typical single-storey extension we handle:
- Knock-through to the existing house with steel beams
- Building control inspections and completion certificate
- Foundations, drainage and any build-over agreement
- First and second fix electrics, heating and plastering
- Cavity walls, insulation and roof to current building regulations
- Measured survey and design drawings
How long does it take?
The build itself usually takes 10 to 14 weeks on site for a typical rear extension, after approvals. Design and approvals come first and typically take 6 to 12 weeks, depending on the approval route.
Building in Berkshire
Commuter towns across the South East have many 1930s and post-war semis that suit rear extensions and hip-to-gable loft conversions.
Towns we cover in Berkshire include Reading, Slough, Bracknell, Maidenhead, Wokingham and Newbury.
How it works
- 01
Free visit
We look at the property, talk through what you want and measure up. There is no charge and no obligation.
- 02
Design and fixed quote
Drawings, structural calculations and an itemised, fixed price for the agreed specification.
- 03
Approvals
Planning or permitted development confirmation, building regulations and any party wall matters.
- 04
Construction and completion
We build, put right any snags and hand over the building control certificate.
Questions about single-storey extensions in Berkshire
How much does a single-storey extension cost in Berkshire?
In Berkshire, a single-storey extension typically costs £2,200–£3,250 per m² of floor area, including VAT at 20% (standard rate). A typical 20 m² project comes to roughly £44,000–£65,000. Your fixed price depends on the survey and drawings.
How long does a single-storey extension take?
Once approvals are in place, a typical rear extension takes 10 to 14 weeks on site. Design and approvals usually take another 6 to 12 weeks beforehand, depending on whether a planning application is needed.
What is a build-over agreement?
If a public sewer runs within 3 metres of the extension, the water company normally has to agree to the work before it starts. We check sewer records during design and apply where needed.
Is VAT charged on an extension?
Yes. Building work on an existing home is standard-rated, so VAT at 20% applies. Our guide prices include it.
Who approves a single-storey extension in Berkshire?
Planning matters in Berkshire go to the council covering your address, and the work needs building control approval. We prepare and submit the applications for you.