Annexe extensions in Swindon: design, approvals and build
A annexe extension in Swindon starts with the right design and the right approval route. We take care of both, then build it with our own project management.
- Guide price in SwindonFrom £56,000 inc VAT
- PlanningUsually a householder application
- Build time16–24 weeks on site
- Postcode districtsSN1, SN2, SN3, SN4, SN5
When an annexe extension makes sense
- Relatives who need support close by
- Homes with a large side or rear garden
- Multi-generational families
Accessibility is cheaper to design in than to retrofit. Level access, a 900 mm door width, a level-access shower and space to turn a wheelchair can all be planned into the footprint for little extra cost.
Do I need planning permission in Swindon?
In England an annexe that stays part of the household and connects to the house is assessed as an extension, but its size usually takes it beyond permitted development, so a householder application describing the ancillary use is the normal route.
Homes in conservation areas, national parks, National Landscapes (formerly AONBs), the Broads and World Heritage Sites have tighter rules, so we always check the property's status and planning history before design starts.
If the work involves a shared wall, building on the boundary, or digging foundations within 3 m (sometimes 6 m) of a neighbour's building, the Party Wall etc. Act 1996 applies and notice must be served before work starts: two months for work to a party wall, one month for new walls on the boundary and for excavations.
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).
Working in Swindon
Site visits are available across Swindon (SN1, SN2, SN3, SN4, SN5, SN25). Neighbouring towns we cover include Calne (12 miles), Chippenham (16 miles), Devizes (18 miles), Melksham (20 miles).
Just over the Gloucestershire border, Cirencester is about 14 miles away. South West homes range from terraced streets in the cities to stone cottages and bungalows in the countryside, and conservation areas are common in historic centres.
What should I budget for an annexe extension in Swindon?
Labour and material costs vary across the UK, so for Swindon we use our South West England factor (×1.02). The ranges include VAT and exclude design, structural and council fees.
Typical rates in Swindon: £2,040 to £3,880 per m² including VAT, depending on specification.
| Size | Essential | Standard | Premium |
|---|---|---|---|
| Studio annexe 25 m² | £56,000 – £70,500 | £61,000 – £76,500 | £76,500 – £97,000 |
| One-bedroom annexe 35 m² | £71,000 – £89,500 | £85,500 – £107,500 | £107,000 – £136,000 |
| Larger annexe 45 m² | £91,500 – £115,000 | £110,000 – £138,000 | £137,500 – £174,500 |
Want a range for your exact size? The guide-price tool takes about a minute.
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
First, a site visit: we look at the house, garden, access and drains and listen to what you need.
Design and approvals
Once the layout is agreed, we deal with the council: planning permission or written confirmation that none is needed, plus building control.
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.
Questions people ask about annexe extensions
Can I see a price before committing to anything?
Yes. The guide prices on this page are adjusted for Swindon, 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 I need building regulations approval in Swindon?
Yes. Almost every extension needs it, whatever the planning route. We prepare the drawings and book the inspections.
How long does an annexe extension take to build in Swindon?
On site, typically 16 to 24 weeks once approvals are in place. Before that, allow 10–16 weeks design and approvals.
How much does an annexe extension cost?
Our guide range is about £2,040 to £3,880 per m² including VAT. A one-bedroom annexe of about 35 m² is typically £85,500 to £107,500 at standard spec in Swindon.
Does an annexe extension need planning permission?
Usually yes, because of its size and the way it will be used. Councils check that it stays ancillary to the main house, so the application must describe the use clearly.
Book a free site visit in Swindon
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.