What is a side return extension?
A side return extension fills the narrow passage that runs alongside the back addition of many Victorian and Edwardian terraced houses. It widens a galley kitchen into a proper kitchen-diner, usually with a sloping glazed roof to keep the room bright.
How much does a side return extension cost in St Austell?
In St Austell, a side return extension typically costs £2,350–£3,350 per m² of floor area, including VAT at 20% (standard rate). For a typical 12 m² project that is roughly £28,000–£40,000. Building costs in the South West are close to the UK average, so the figures for St Austell are close to our national guide. Design, structural calculations and council fees are extra.
| Size or type | Guide range |
|---|---|
| Smaller project (8 m²) | £19,000–£27,000 |
| Typical project (12 m²) | £28,000–£40,000 |
| Larger project (17 m²) | £40,000–£57,000 |
| Rate per m² | £2,350–£3,350 |
What moves the price most:
- Length of the side return
- Steel beams and propping of the back addition
- Moving drains and soil stacks
- Access through the house for materials
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 side return extension in St Austell?
Before anything is built in St Austell, we confirm which approvals apply in England. In England a side return infill is treated as a side extension. It may be permitted development if it is single-storey, no more than 4 metres high and no wider than half the original house, but not in a conservation area. Because side returns sit on the boundary, party wall notices are almost always needed.
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 side return extension we handle:
- Glazed or solid roof with insulation
- Party wall advice and notices
- Survey of party walls, drains and the existing back addition
- Steel beams to remove the side wall
- Drawings and planning or permitted development check
- Floor levelling, heating and electrics
How long does it take?
Expect 10 to 14 weeks on site. Before that, surveys, drawings and approvals usually take 3 to 4 months, longer if the council asks for changes.
Building in St Austell
In parts of the South West, protected landscapes and conservation areas shape what can be built, so materials and roof forms are chosen carefully.
From PL25 outwards, we take on projects throughout St Austell and the surrounding parts of Cornwall.
How it works
- 01
Visit and measured survey
A free visit to understand the project, check access and take measurements.
- 02
Drawings and written quote
We prepare the design and give you a written, itemised quote with inclusions and exclusions.
- 03
Approvals in place
We handle planning, building control and neighbour notices before work starts.
- 04
Construction and completion
We build, put right any snags and hand over the building control certificate.
Questions about side return extensions in St Austell
Will I need a party wall agreement?
Almost certainly in England and Wales, because side returns sit on or near the boundary. Notices must be served before work starts, and a party wall surveyor may be appointed if the neighbour does not consent.
Can I stay in the house?
Usually, though the kitchen will be out of action for several weeks. We plan a temporary kitchen area where possible.
How much does a side return extension cost in St Austell?
In St Austell, a side return extension typically costs £2,350–£3,350 per m² of floor area, including VAT at 20% (standard rate). A typical 12 m² project comes to roughly £28,000–£40,000. Your fixed price depends on the survey and drawings.
Who approves a side return extension in St Austell?
Planning matters in St Austell go to the council covering your address, and the work needs building control approval. We prepare and submit the applications for you.
Is a glass roof too hot or cold?
Modern solar-control double or triple glazing reduces glare and heat loss. Building regulations also limit how much glazing you can have unless the design shows it performs well enough.