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 Letchworth Garden City?
In Letchworth Garden City, a side return extension typically costs £2,450–£3,500 per m² of floor area, including VAT at 20% (standard rate). For a typical 12 m² project that is roughly £29,500–£42,000. That range is adjusted for the East of England, where domestic building work typically costs around 6% above the national average. Design, structural calculations and council fees are extra.
| Size or type | Guide range |
|---|---|
| Smaller project (8 m²) | £19,500–£28,000 |
| Typical project (12 m²) | £29,500–£42,000 |
| Larger project (17 m²) | £41,500–£59,500 |
| Rate per m² | £2,450–£3,500 |
The biggest cost drivers are:
- Length of the side return
- Party wall surveyor fees
- Access through the house for materials
- Glazed roof specification
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 Letchworth Garden City?
The approval route for Letchworth Garden City is set by planning law 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.
Our first visit includes a check of your planning history, so you know the route before paying for drawings.
What we handle
From survey to sign-off, the job normally involves:
- Survey of party walls, drains and the existing back addition
- Glazed or solid roof with insulation
- Floor levelling, heating and electrics
- Building control sign-off
- Foundations and drainage, including any build-over agreement
- Drawings and planning or permitted development check
How long does it take?
The build itself usually takes 10 to 14 weeks on site. Allow time beforehand for drawings and approvals, usually 3 to 4 months.
Building in Letchworth Garden City
Across the East of England, 1930s and post-war semis, newer estates and rural cottages all feature, each with different extension and loft options.
If your home is in Letchworth Garden City or close by in Hitchin, Stevenage and Luton, a free home visit is the first step.
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
Permissions sorted
Applications, building control and neighbour arrangements, all before the start date.
- 04
Build and handover
Work follows the agreed programme, with inspections along the way and a completion certificate at the end.
Questions about side return extensions in Letchworth Garden City
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.
How much does a side return extension cost in Letchworth Garden City?
In Letchworth Garden City, a side return extension typically costs £2,450–£3,500 per m² of floor area, including VAT at 20% (standard rate). A typical 12 m² project comes to roughly £29,500–£42,000. Your fixed price depends on the survey and drawings.
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.
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.
Who approves a side return extension in Letchworth Garden City?
Planning matters in Letchworth Garden City go to the council covering your address, and the work needs building control approval. We prepare and submit the applications for you.