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 Bath?
In Bath, 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. Prices in the South West sit near the national average for this kind of work, and the range for Bath reflects that. 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:
- Size and layout
- Access for materials
- Kitchen and bathroom
- Drainage connection distance
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 Bath?
Before anything is built in Bath, we confirm which approvals apply in 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.
We check this for your address before design work starts, so there are no surprises later.
What we handle
Handled as part of most garden annexes:
- Insulated walls and roof
- Building control sign-off
- Planning drawings and application
- Electrics and heating
- Kitchenette and shower room
- External cladding or brickwork
How long does it take?
Build time is typically 10 to 16 weeks on site. Design and approvals come first and typically take 3 to 4 months, depending on the approval route.
Building in Bath
In parts of the South West, protected landscapes and conservation areas shape what can be built, so materials and roof forms are chosen carefully.
Our Bath coverage includes postcode districts BA1, and we also work in nearby places such as Keynsham, Trowbridge and Kingswood.
How it works
- 01
Visit and measured survey
A free visit to understand the project, check access and take measurements.
- 02
Drawings and written quote
We prepare the design and give you a written, itemised quote with inclusions and exclusions.
- 03
Approvals in place
We handle planning, building control and neighbour notices before work starts.
- 04
Build and handover
Work follows the agreed programme, with inspections along the way and a completion certificate at the end.
Questions about garden annexes in Bath
Can an annexe be rented out?
Not without further planning permission, as that would make it a separate dwelling.
How long does a garden annexe take in Bath?
Typically 10 to 16 weeks on site. Design and approvals beforehand usually take 3 to 4 months.
Can it be accessible?
Yes. Level access, wider doors and a wet room can be designed in.
How much does a garden annexe cost in Bath?
In Bath, 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.