St Austell, Cornwall
Single-storey rear extension in St Austell
Ground-floor space across the back of the house, usually for a kitchen, dining or family room. If you live in St Austell and want to know what a single-storey rear extension would cost and whether it needs planning, start with the online guide price or a free site visit.
St Austell is covered from our Cornwall round, including PL25. A single-storey rear extension in St Austell 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 St Austell?
For St Austell we work from the South West England rate: £1,980–£3,220 per square metre of new floor, including VAT, standard specification. South West prices run slightly above our West Midlands baseline; natural stone to match the house is the main variable.
| Size | Guide price inc VAT |
|---|---|
| 3 m wide × 4 m deep (12 m²) | £23,500–£38,500 |
| 4 m wide × 5 m deep (20 m²) | £39,500–£64,500 |
| 4 m wide × 6 m deep (24 m²) | £47,500–£77,500 |
We put a fixed price in writing once the design is agreed, and explain any provisional sums such as foundations.
Do you need planning permission for a single-storey rear extension in St Austell?
The planning route for a single-storey rear extension in St Austell is set by England's householder rules and your council.
English permitted development (Class A) allows a single-storey rear extension of 3 metres on a terraced or semi-detached house and 4 metres on a detached one, measured from the original house, with a maximum height of 4 metres and eaves of no more than 3 metres within 2 metres of a boundary.
If 3 or 4 metres is not enough, England's prior approval route allows 6 metres on a terraced or semi-detached house and 8 metres on a detached house for a single-storey rear extension. Neighbours are consulted, the council decides within 42 days, and the fee is £249, rising to £310 from 8 December 2026.
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 St Austell like to extend?
Stone-built and rendered houses are common around St Austell, so matching the walling is a design decision in its own right: natural stone, reconstituted stone or a render finish across old and new.
How a single-storey rear extension in St Austell 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.
Paperwork handled
Planning, prior approval or permitted development, Building Regulations approval, structural design and party wall notices are all handled by us.
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 St Austell
Close by, we work in Bodmin, about 9.2 miles away, and Truro, about 13.5 miles away.
- Single-storey rear extension in Bodmin
- Single-storey rear extension in Truro
- Single-storey rear extension in Newquay
- Single-storey rear extension in Falmouth
- Single-storey rear extension in Redruth
Other work in St Austell:
FAQ
Single-storey rear extension questions in St Austell
Do I need planning permission for a rear extension in St Austell?
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.
Do I need a party wall agreement?
In England, usually yes if the extension is on or near a shared boundary or the foundations are close to a neighbour's building. We serve the notices.
Does it add value to the house?
Nationwide's October 2025 house price research found that a 10% increase in floor area is linked to about 5% higher value on average. It is a guide, not a promise; local agents can tell you what extended homes on your street sell for.
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.
Can I live at home while the extension is built?
Usually yes. Most of the work is outside until the back wall is opened near the end, and that stage is screened off.
Can I get a price without a visit?
Our online guide-price tool gives a range in a couple of minutes. A written price needs a survey.