House extensions in Thornbury
Looking to extend your home in Thornbury? Start here: extension types, guide prices for Thornbury, the planning rules that apply and how a project runs.
- Postcode districtsBS35
- Price regionSouth West England (×1.02)
- Planning rulesEngland
- Site visitFree, no obligation
Planning rules in Thornbury
In England a single-storey rear extension can usually go up to 3 m beyond the original rear wall of a semi-detached or terraced house, or 4 m on a detached house, without a planning application, provided it is no more than 4 m high, keeps eaves to 3 m within 2 m of a boundary and, with other buildings, covers no more than half the land around the original house. The larger home extension prior approval scheme raises those depths to 6 m and 8 m, with neighbours notified and a 42-day decision.
In England a single-storey side extension can be permitted development if it is no more than 4 m high and no wider than half the width of the original house. Two-storey side extensions, and any side extension on designated land such as a conservation area, need a householder planning application.
In a conservation area, national park, National Landscape, the Broads or a World Heritage Site the permitted development limits are tighter (no side or two-storey extensions without an application). Listed homes need listed building consent, and if permitted development rights have been removed, any extension needs an application.
If the work involves a shared wall, building on the boundary, or digging foundations within 3 m (sometimes 6 m) of a neighbour's building, the Party Wall etc. Act 1996 applies and notice must be served before work starts: two months for work to a party wall, one month for new walls on the boundary and for excavations.
Applications are decided by the local planning authority (your district, borough or unitary council).
Areas we cover around Thornbury
We cover Thornbury and the postcode districts BS35. The same team covers Yate (7 miles), Mangotsfield (8 miles), Kingswood (10 miles), Dursley (10 miles), Stroud (18 miles), all within easy reach. Portishead, in Somerset, is roughly 12 miles from Thornbury and also on our list.
Which extension suits a Thornbury home?
In the South West, local stone, render and brick vary from town to town, so matching materials is a big part of designing an extension that looks right.
The types we would usually look at first for a home in Thornbury are single-storey rear extensions, annexe extensions and pitched roof extensions, depending on the garden and how the house is laid out.
What extensions cost in Thornbury
Prices on this page use our South West England factor of ×1.02, include VAT at 20% and cover the build; your written price follows a survey and agreed drawings.
| Extension type | Example size | Standard spec (inc VAT) |
|---|---|---|
| Orangery extensions | 16 m² | £45,500 – £57,500 |
| Kitchen extensions | 20 m² | £42,500 – £54,500 |
| Wraparound extensions | 25 m² | £58,500 – £74,000 |
| Side return extensions | 11 m² | £26,500 – £34,000 |
| Conservatory replacement extensions | 14 m² | £30,500 – £39,500 |
All extension types we build in Thornbury
- Extension plans and drawings · from £1,200
- Flat roof extensions · from £21,000
- Extensions over a garage · from £24,000
- Bedroom extensions · from £26,500
- Timber frame extensions · from £21,000
- Annexe extensions · from £56,000
- Single-storey rear extensions · from £21,000
- Double-storey extensions · from £38,500
- Orangery extensions · from £30,500
- Side extensions · from £22,000
- Conservatory replacement extensions · from £20,000
- Utility and boot room extensions · from £14,000
- Wraparound extensions · from £36,500
- Side return extensions · from £18,000
- Planning permission for extensions · from £350
- Pitched roof extensions · from £22,500
- Home office extensions · from £16,000
- Porch extensions · from £4,050
- Building regulations for extensions · from £900
- Kitchen extensions · from £27,500
- Bungalow extensions · from £26,500
- Glass box extensions · from £30,500
Free site visit
A designer visits, takes measurements and photos, and discusses layouts, budget and timing with you.
Design and approvals
Once the layout is agreed, we deal with the council: planning permission or written confirmation that none is needed, plus building control.
Fixed written price
The price is fixed in writing once the design is settled, with a clear programme and payment stages.
Build and sign-off
The build is managed from start to finish, inspected at each stage and signed off on completion.
Questions about extensions in Thornbury
How much does an extension cost in Thornbury?
Using our South West England factor (×1.02), a standard-spec single-storey extension of 20 m² is a guide £41,500 to £53,500 including VAT, and a 32 m² two-storey extension £58,500 to £77,000. Your written price follows the survey.
Do you handle building regulations?
Yes. We prepare the drawings and calculations, submit them and book inspections, ending with a completion certificate.
How long does an extension take in Thornbury?
Usually 2 to 4 months of design and approvals, then 10 to 16 weeks on site for a single-storey extension or 16 to 24 weeks for two storeys.
Do I need planning permission for an extension in Thornbury?
Not always. It depends on the size, position and your property's history. Many single-storey rear extensions in England are permitted development or can use prior approval.
Will my neighbours need to be told?
If you apply for planning or prior approval the council notifies them, and in England party wall notices may be needed for work near a shared boundary.
Book a free site visit in Thornbury
We will measure up, check the planning position and give you honest guide figures.
- Free, no-obligation site visit
- Planning route checked before you spend on drawings
- Written price once the design is agreed
- Building control sign-off at the end
Prefer to talk? Call 0800 088 6341 or .
Book a free site visit
Tell us a little about the project and we will arrange a time.