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 County Durham?
In County Durham, a garden annexe typically costs £1,600–£2,500 per m² of floor area, including VAT at 20% (standard rate). For a typical 35 m² project that is roughly £56,000–£87,500. Building costs in the North East run about 10% below the UK average, and the figures for County Durham are adjusted to reflect that. Design, structural calculations and council fees are extra.
| Size or type | Guide range |
|---|---|
| Smaller project (24 m²) | £38,500–£60,000 |
| Typical project (35 m²) | £56,000–£87,500 |
| Larger project (49 m²) | £78,500–£122,500 |
| Rate per m² | £1,600–£2,500 |
What moves the price most:
- Heating type
- Size and layout
- Kitchen and bathroom
- Cladding and finishes
Your exact price depends on the survey and drawings. The guide price tool gives a quick range in the meantime.
Do you need planning permission for a garden annexe in County Durham?
Here is how the rules work for a garden annexe 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:
- External cladding or brickwork
- Kitchenette and shower room
- Glazed doors and windows
- Foundations and drainage connections
- Building control sign-off
- Insulated walls and roof
How long does it take?
The build itself usually takes 10 to 16 weeks on site. Allow time beforehand for drawings and approvals, usually 3 to 4 months.
Building in County Durham
The North East has many terraced streets and post-war semis, where rear extensions and loft conversions are popular ways to gain space.
Towns we cover in County Durham include Darlington, Hartlepool, Stockton-on-Tees, Durham, Chester-le-Street and Billingham.
How it works
- 01
Survey and brief
We visit, discuss your ideas and budget, and survey the property or site at no cost.
- 02
Design and fixed quote
Drawings, structural calculations and an itemised, fixed price for the agreed specification.
- 03
Permissions sorted
Applications, building control and neighbour arrangements, all before the start date.
- 04
Construction and completion
We build, put right any snags and hand over the building control certificate.
Questions about garden annexes in County Durham
Can an annexe be rented out?
Not without further planning permission, as that would make it a separate dwelling.
Do you build garden annexes in County Durham?
Yes. We build garden annexes across County Durham, including postcodes DH1, DH2, DH3, DH4 and DH6. Every project starts with a free home visit.
Does a garden annexe need planning permission?
Usually yes if it is used as living accommodation. Outbuildings under permitted development must be incidental to the house, such as a gym or office, not bedrooms.
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 County Durham?
In County Durham, a garden annexe typically costs £1,600–£2,500 per m² of floor area, including VAT at 20% (standard rate). A typical 35 m² project comes to roughly £56,000–£87,500. Your fixed price depends on the survey and drawings.