Cornwall
Single-storey rear extensions in Cornwall
Ground-floor space across the back of the house, usually for a kitchen, dining or family room. Across Cornwall we handle the whole rear extension: survey, drawings, the planning route, building control and the build. Towns we cover here include Redruth, Falmouth and St Austell.
On Victorian terraces and post-war semis like those around Redruth, a single-storey rear extension is usually the simplest way to fix a small back kitchen without touching the bedrooms. Cornwall has Victorian terraces nearer the centre and post-war semis on the edges. Sloping gardens are frequent, which affects floor levels and steps down to the patio.
How much does a single-storey rear extension cost in Cornwall?
A single-storey rear extension in Cornwall is priced at £1,980–£3,220 per square metre including VAT as a guide, before kitchen fit-out and fees. 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 |
Ground conditions, glazing, the roof and how far the house is opened up move the final figure within the range.
Do you need planning permission in Cornwall?
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.
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.
Where in Cornwall do we work?
FAQ
Questions people ask
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.
Is a flat roof or a pitched roof better?
A warm flat roof keeps the extension low under first-floor windows and suits a roof lantern; a pitched or lean-to roof gives a vaulted ceiling. Both last for decades when built properly.
Can I stay in the house during the build?
Usually yes. The noisiest, dustiest stage, removing the back wall, is kept to the final weeks and screened off. Most families set up a temporary kitchen elsewhere in the house.
Do you cover all of Cornwall?
We cover 10 towns and districts in Cornwall, including Redruth, Falmouth and St Austell.
Who builds the extension?
Vetted building teams working under contract to us; your contract is with S&K Property Investments and Improvement Ltd.