Wraparound extensions in Welwyn Garden City: design, approvals and build
If you live in Welwyn Garden City and want more space without moving, a wraparound extension is one of the most practical ways to get it. We handle the drawings, approvals and the build.
- Guide price in Welwyn Garden CityFrom £38,000 inc VAT
- PlanningUsually a householder application
- Build time14–20 weeks on site
- Postcode districtsAL6, AL7, AL8, AL10
What is included
- Foundations, drainage and any manhole relocation
- Party wall notice support (England and Wales)
- Roof with glazing along the side return
- Survey, design and 3D layout options
The corner is where wraparounds succeed or fail. We usually use a single steel goalpost or a corner post hidden in a pier, and set the glazing so the new room reads as one space rather than two boxes.
What should I budget for a wraparound extension in Welwyn Garden City?
Labour and material costs vary across the UK, so for Welwyn Garden City we use our East of England factor (×1.06). The ranges include VAT and exclude design, structural and council fees.
Typical rates in Welwyn Garden City: £2,120 to £3,920 per m² including VAT, depending on specification.
| Size | Essential | Standard | Premium |
|---|---|---|---|
| Compact L-shape 18 m² | £38,000 – £46,000 | £43,500 – £55,500 | £55,000 – £71,000 |
| Medium L-shape 25 m² | £53,000 – £64,000 | £60,500 – £77,000 | £76,500 – £98,500 |
| Large L-shape 32 m² | £67,500 – £81,500 | £78,000 – £98,500 | £98,000 – £126,000 |
For a figure based on your own dimensions, use our guide-price tool.
Working in Welwyn Garden City
Across AL6, AL7, AL8, AL10, we can visit, measure and advise. Neighbouring towns we cover include Hatfield (3 miles), Hertford (6 miles), St Albans (6 miles), Harpenden (6 miles).
For homes towards Bedfordshire, Luton is around 10 miles away. The East of England mixes market-town terraces, inter-war semis and modern estates. Clay soils are common in parts of the region, which can affect foundation design.
Planning and approvals in Welwyn Garden City
In England a wraparound extension is assessed as both a side and a rear extension, and the combination usually falls outside permitted development, so most need a householder planning application (£548 from 1 April 2026).
In a conservation area, national park, National Landscape, the Broads or a World Heritage Site the permitted development limits are tighter (no side or two-storey extensions without an application). Listed homes need listed building consent, and if permitted development rights have been removed, any extension needs an application.
Building over or within 3 m of a public sewer needs the water company's consent, usually through a build-over agreement, before the foundations go in.
Applications are decided by the local planning authority (your district, borough or unitary council).
How the project works
Site visits are free and there is no obligation. Where drawings are needed, the design stage is priced in writing before it starts.
Free site visit
We visit your Welwyn Garden City home, measure up, talk through what you want and check the planning position.
Design and approvals
Drawings are prepared and agreed with you, then submitted for the right planning route and building regulations approval.
Fixed written price
You receive a written, itemised price and programme. Nothing starts until you are happy with it.
Build and sign-off
The build is managed from start to finish, inspected at each stage and signed off on completion.
Your questions about a wraparound extension in Welwyn Garden City
How long does a wraparound extension take to build in Welwyn Garden City?
On site, typically 14 to 20 weeks once approvals are in place. Before that, allow 8–16 weeks design and approvals.
Can I see a price before committing to anything?
Yes. The guide prices on this page are adjusted for Welwyn Garden City, and the guide-price tool gives a range for your own size. After the survey you get a written price before anything is agreed.
Do you cover all of Welwyn Garden City?
Yes. We cover Welwyn Garden City and the surrounding parts of Hertfordshire. Site visits are free and there is no obligation.
Will I need to move a drain?
Often. Side returns frequently contain a manhole or a shared drain. Building near or over a public sewer needs the water company’s consent in England and Wales, which we arrange.
How much does a wraparound extension cost?
Our guide range is about £2,120 to £3,920 per m² including VAT. A 25 m² standard-spec wraparound typically lands around £60,500 to £77,000 in Welwyn Garden City before design and council fees.
Book a free site visit in Welwyn Garden City
We will measure up, check the planning position and give you honest guide figures.
- Free, no-obligation site visit
- Planning route checked before you spend on drawings
- Written price once the design is agreed
- Building control sign-off at the end
Prefer to talk? Call 0800 088 6341 or .
Book a free site visit
Tell us a little about the project and we will arrange a time.