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 Welwyn Garden City?
In Welwyn 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. We start from a UK-wide guide and adjust it for the East of England, where labour and materials are typically about 6% above 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 main things that change the cost:
- Access through the house for materials
- Party wall surveyor fees
- Glazed roof specification
- Length of the side return
For a figure based on your own measurements, try the guide price tool, then book a free home visit for a fixed quote.
Do you need planning permission for a side return extension in Welwyn Garden City?
Here is how the rules work for a side return extension 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.
If the answer is not clear-cut, we can apply for formal confirmation before you commit to the build.
What we handle
The work we manage on a side return extension:
- Floor levelling, heating and electrics
- Foundations and drainage, including any build-over agreement
- Party wall advice and notices
- Steel beams to remove the side wall
- Glazed or solid roof with insulation
- Drawings and planning or permitted development check
How long does it take?
Allow 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 Welwyn 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.
Our Welwyn Garden City coverage includes postcode districts AL8, and we also work in nearby places such as Hatfield, Hertford and St Albans.
How it works
- 01
Survey and brief
We visit, discuss your ideas and budget, and survey the property or site at no cost.
- 02
Design and pricing
Design options, then a fixed quote based on the chosen drawings and 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 Welwyn Garden City
Do you build side return extensions in Welwyn Garden City?
Yes. We build side return extensions across Welwyn Garden City, including postcodes AL8. Every project starts with a free home visit.
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.
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 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.
How much does a side return extension cost in Welwyn Garden City?
In Welwyn 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.