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 Southampton?
In Southampton, a side return extension typically costs £2,600–£3,700 per m² of floor area, including VAT at 20% (standard rate). For a typical 12 m² project that is roughly £31,000–£44,500. Building costs in the South East run about 12% above the UK average, and the figures for Southampton are adjusted to reflect that. Design, structural calculations and council fees are extra.
| Size or type | Guide range |
|---|---|
| Smaller project (8 m²) | £21,000–£29,500 |
| Typical project (12 m²) | £31,000–£44,500 |
| Larger project (17 m²) | £44,000–£63,000 |
| Rate per m² | £2,600–£3,700 |
The biggest cost drivers are:
- Party wall surveyor fees
- Glazed roof specification
- Steel beams and propping of the back addition
- Access through the house for materials
Your exact price depends on the survey and drawings. The guide price tool gives a quick range in the meantime.
Do you need planning permission for a side return extension in Southampton?
Before anything is built in Southampton, 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.
Where work involves a shared wall, building on the boundary, or digging foundations within 3 metres of a neighbour’s building and deeper than its foundations (or within 6 metres for deeper work), the Party Wall etc. Act 1996 applies and notices must be served before work starts.
We check this for your address before design work starts, so there are no surprises later.
What we handle
Handled as part of most side return extensions:
- Drawings and planning or permitted development check
- Steel beams to remove the side wall
- Foundations and drainage, including any build-over agreement
- Glazed or solid roof with insulation
- Building control sign-off
- Party wall advice and notices
How long does it take?
Expect 10 to 14 weeks on site. Design and approvals come first and typically take 3 to 4 months, depending on the approval route.
Building in Southampton
The South East has a broad mix of housing, from Victorian terraces in the towns to post-war semis and newer estates, so extension types vary street by street.
Southampton sits in Hampshire, about 12 miles south of Winchester. We cover the whole of Southampton, including postcodes SO15.
How it works
- 01
Visit and measured survey
A free visit to understand the project, check access and take measurements.
- 02
Design and fixed quote
Drawings, structural calculations and an itemised, fixed price for the agreed specification.
- 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 Southampton
How much does a side return extension cost in Southampton?
In Southampton, a side return extension typically costs £2,600–£3,700 per m² of floor area, including VAT at 20% (standard rate). A typical 12 m² project comes to roughly £31,000–£44,500. Your fixed price depends on the survey and drawings.
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 space does a side return add?
Typically 1.5 to 2.5 metres of width along the back addition. It often turns a narrow galley kitchen into a family kitchen-diner.
Do you build side return extensions in Southampton?
Yes. We build side return extensions across Southampton, including postcodes SO15. Every project starts with a free home visit.
How do you get materials in?
Mid-terrace houses often have no rear access, so materials come through the house. We protect floors and plan deliveries carefully.