Annexe extensions in Trowbridge: design, approvals and build
Trowbridge homeowners can use us for the whole annexe extension project: survey, design, planning or permitted development checks, building regulations and the build itself.
- Guide price in TrowbridgeFrom £56,000 inc VAT
- PlanningUsually a householder application
- Build time16–24 weeks on site
- Postcode districtsBA14
Who an annexe extension suits
- Homes with a large side or rear garden
- Multi-generational families
- Relatives who need support close by
Planning rules that apply in Trowbridge
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.
Building regulations approval is separate from planning. In England you can use the council's building control team or a registered building control approver; a full plans application gets the drawings checked before work starts, and the inspector signs the work off with a completion certificate.
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.
Applications are decided by the local planning authority (your district, borough or unitary council).
Covering Trowbridge
Site visits are available across Trowbridge (BA14). The same team covers Melksham (5 miles), Devizes (10 miles), Warminster (10 miles), Chippenham (10 miles), all within easy reach.
Bath, in Somerset, is roughly 8 miles from Trowbridge and also on our list. In the South West, local stone, render and brick vary from town to town, so matching materials is a big part of designing an extension that looks right.
Annexe extension prices in Trowbridge
For Trowbridge we adjust our national guide rates by ×1.02, the factor we use for South West England. Figures include VAT; your written quote after the survey replaces them.
Typical rates in Trowbridge: £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.
What happens next
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
We produce the drawings and structural design, and manage the approvals so they are in place before work starts.
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.
Common questions in Trowbridge
Do you cover all of Trowbridge?
Yes. We cover Trowbridge and the surrounding parts of Wiltshire. Site visits are free and there is no obligation.
How long does an annexe extension take to build in Trowbridge?
On site, typically 16 to 24 weeks once approvals are in place. Before that, allow 10–16 weeks design and approvals.
Who do I contract with for an annexe extension in Trowbridge?
Your contract is with S&K Property Investments and Improvement Ltd, which designs and manages the project and the build teams who carry it out.
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 Trowbridge.
Will an annexe affect council tax?
It can. Some annexes are assessed separately for council tax, with discounts or exemptions in some cases when occupied by a relative. Check with the Valuation Office Agency (England and Wales), your local assessor (Scotland) or Land & Property Services (Northern Ireland).
Book a free site visit in Trowbridge
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.