Annexe extensions across Devon
Thinking about an annexe extension for your Devon home? Start with a free site visit: we measure up, check what the council will allow and give you honest guide figures on the day.
- Guide priceFrom £56,000 inc VAT
- PlanningUsually a householder application
- Towns covered9
- Site visitFree, no obligation
When an annexe extension makes sense
- Homes with a large side or rear garden
- Relatives who need support close by
- 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 Devon?
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.
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 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.
Applications are decided by the local planning authority (your district, borough or unitary council).
What should I budget for an annexe extension in Devon?
These guide figures apply our South West England adjustment (×1.02) to national rates. They include VAT at 20% and cover the build itself; design and council fees are listed separately.
Typical rates in Devon: £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 |
For a figure based on your own dimensions, use our guide-price tool.
Local to Devon
Towns we cover in Devon include Plymouth, Exeter, Paignton, Torquay, Newton Abbot, Exmouth, Barnstaple, Bideford. 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.
Our process, step by step
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
A designer visits, takes measurements and photos, and discusses layouts, budget and timing with you.
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
With the design and specification agreed, you get a fixed written price and a start date.
Build and sign-off
We build it with one project manager, book the building control inspections and hand over the completion certificate.
Questions people ask about annexe extensions
Do you cover all of Devon?
Yes, across the whole of Devon. Site visits are free and there is no obligation.
Can I see a price before committing to anything?
Yes. The guide prices on this page are adjusted for Devon, and the guide-price tool gives a range for your own size. After the survey you get a written price before anything is agreed.
Will my neighbours in Devon be involved?
If a planning application or prior approval is needed, the council notifies neighbours. If the work is on or near a shared boundary, party wall notices may also be needed.
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.
Can the annexe have its own front door?
Yes, many do, but it should still connect to the main house to stay clearly part of it.
Book a free site visit in Devon
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.