What is a garden annexe?
A garden annexe is a single-storey building in the garden with its own living space, bathroom and often a kitchenette, used by relatives, older children or guests. Unlike a garden room, it is built as habitable accommodation with foundations, insulation and services.
How much does a garden annexe cost in Devon?
In Devon, a garden annexe typically costs £1,850–£2,850 per m² of floor area, including VAT at 20% (standard rate). For a typical 35 m² project that is roughly £65,000–£100,000. Building costs in the South West are close to the UK average, so the figures for Devon are close to our national guide. Design, structural calculations and council fees are extra.
| Size or type | Guide range |
|---|---|
| Smaller project (24 m²) | £44,500–£68,500 |
| Typical project (35 m²) | £65,000–£100,000 |
| Larger project (49 m²) | £90,500–£139,500 |
| Rate per m² | £1,850–£2,850 |
What moves the price most:
- Access for materials
- Drainage connection distance
- Kitchen and bathroom
- Size and layout
A guide range is only a starting point: the guide price tool gives an instant figure for your size, and a free survey turns it into a fixed quote.
Do you need planning permission for a garden annexe in Devon?
Approvals for a garden annexe in Devon follow the rules for England. In England an annexe used as living accommodation usually needs planning permission. Outbuildings built under permitted development must be incidental to the house, such as a gym or office, not a bedroom.
Building regulations approval comes from the council’s building control service or a registered building control approver. The work is inspected at key stages, such as foundations, drainage and insulation, and a completion certificate is issued at the end.
If the answer is not clear-cut, we can apply for formal confirmation before you commit to the build.
What we handle
What we take care of:
- Glazed doors and windows
- Foundations and drainage connections
- External cladding or brickwork
- Planning drawings and application
- Kitchenette and shower room
- Electrics and heating
How long does it take?
Allow 10 to 16 weeks on site. Allow time beforehand for drawings and approvals, usually 3 to 4 months.
Building in Devon
The South West mixes stone and render cottages with post-war and newer estates, and local materials matter more here when matching an extension.
Towns we cover in Devon include Plymouth, Exeter, Paignton, Torquay, Newton Abbot and Exmouth.
How it works
- 01
Survey and brief
We visit, discuss your ideas and budget, and survey the property or site at no cost.
- 02
Drawings and written quote
We prepare the design and give you a written, itemised quote with inclusions and exclusions.
- 03
Approvals
Planning or permitted development confirmation, building regulations and any party wall matters.
- 04
Build and sign-off
We run the build to a written programme and hand over the completion certificate.
Questions about garden annexes in Devon
Do you build garden annexes in Devon?
Yes. We build garden annexes across Devon, including postcodes DT7, EX1, EX10, EX11 and EX12. Every project starts with a free home visit.
How much does a garden annexe cost in Devon?
In Devon, a garden annexe typically costs £1,850–£2,850 per m² of floor area, including VAT at 20% (standard rate). A typical 35 m² project comes to roughly £65,000–£100,000. Your fixed price depends on the survey and drawings.
Will council tax apply?
Annexes can be banded separately, though discounts or exemptions apply in some cases when occupied by family. Check with your council.
Can it be accessible?
Yes. Level access, wider doors and a wet room can be designed in.
Can an annexe be rented out?
Not without further planning permission, as that would make it a separate dwelling.