St Austell house extensions
Every type of house extension in St Austell, from single-storey kitchen extensions to two-storey additions, side returns and orangeries. We design, handle the approvals and build.
- Postcode districtsPL25
- Price regionSouth West England (×1.02)
- Planning rulesEngland
- Site visitFree, no obligation
Covering St Austell and nearby
We cover St Austell and the postcode districts PL25. Neighbouring towns we cover include Bodmin (9 miles), Truro (13 miles), Newquay (14 miles), Falmouth (18 miles), Redruth (21 miles). Plymouth, in Devon, is roughly 28 miles from St Austell and also on our list.
Do extensions in St Austell need planning permission?
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 two-storey rear extension is permitted development only if it projects no more than 3 m from the original rear wall, sits at least 7 m from the rear boundary, matches the roof pitch and uses obscure, non-opening side windows upstairs. Most two-storey extensions therefore go through a householder planning application, which costs £548 from 1 April 2026 and normally takes about 8 weeks.
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.
Building regulations approval is separate from planning. In England you can use the council's building control team or a registered building control approver; a full plans application gets the drawings checked before work starts, and the inspector signs the work off with a completion certificate.
Applications are decided by the local planning authority (your district, borough or unitary council).
Popular extension prices in St Austell
Use these St Austell guide prices to sense-check a budget; the guide-price tool narrows them to your own size, and the site visit turns them into a written figure.
| Extension type | Example size | Standard spec (inc VAT) |
|---|---|---|
| Extensions over a garage | 12 m² | £25,500 – £33,500 |
| Side return extensions | 11 m² | £26,500 – £34,000 |
| Wraparound extensions | 25 m² | £58,500 – £74,000 |
| Single-storey rear extensions | 20 m² | £41,500 – £53,500 |
| Conservatory replacement extensions | 14 m² | £30,500 – £39,500 |
| Double-storey extensions | 32 m² | £58,500 – £77,000 |
| Kitchen extensions | 20 m² | £42,500 – £54,500 |
Choosing the right extension in St Austell
South West homes range from terraced streets in the cities to stone cottages and bungalows in the countryside, and conservation areas are common in historic centres.
The types we would usually look at first for a home in St Austell are annexe extensions, orangery extensions and pitched roof extensions, depending on the garden and how the house is laid out.
Choose an extension type
- Glass box extensions · from £30,500
- Orangery extensions · from £30,500
- Annexe extensions · from £56,000
- Kitchen extensions · from £27,500
- Porch extensions · from £4,050
- Side return extensions · from £18,000
- Bungalow extensions · from £26,500
- Extensions over a garage · from £24,000
- Side extensions · from £22,000
- Utility and boot room extensions · from £14,000
- Flat roof extensions · from £21,000
- Planning permission for extensions · from £350
- Double-storey extensions · from £38,500
- Timber frame extensions · from £21,000
- Building regulations for extensions · from £900
- Wraparound extensions · from £36,500
- Conservatory replacement extensions · from £20,000
- Single-storey rear extensions · from £21,000
- Extension plans and drawings · from £1,200
- Home office extensions · from £16,000
- Pitched roof extensions · from £22,500
- Bedroom extensions · from £26,500
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
You receive a written, itemised price and programme. Nothing starts until you are happy with it.
Build and sign-off
We build it with one project manager, book the building control inspections and hand over the completion certificate.
Questions about extensions in St Austell
How much does an extension cost in St Austell?
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.
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.
Can I get a price before anyone visits?
Yes. This page shows guide prices adjusted for St Austell, and the guide-price tool gives a range for your own size and finish in about a minute.
Do you cover all of St Austell?
Yes, including the surrounding parts of Cornwall. Site visits are free and there is no obligation.
Book a free site visit in St Austell
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.