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 Antrim?
In County Antrim, a garden annexe typically costs £1,550–£2,400 per m² of floor area, including VAT at 20% (standard rate). For a typical 35 m² project that is roughly £54,000–£84,000. Prices across Northern Ireland are typically 14% below the UK average for this kind of work, which is reflected in the range for County Antrim. Design, structural calculations and council fees are extra.
| Size or type | Guide range |
|---|---|
| Smaller project (24 m²) | £37,000–£57,500 |
| Typical project (35 m²) | £54,000–£84,000 |
| Larger project (49 m²) | £76,000–£117,500 |
| Rate per m² | £1,550–£2,400 |
The main things that change the cost:
- Cladding and finishes
- Access for materials
- Size and layout
- Heating type
For a figure based on your own measurements, try the guide price tool, then book a free home visit for a fixed quote.
Do you need planning permission for a garden annexe in County Antrim?
The approval route for County Antrim is set by planning law in Northern Ireland. In Northern Ireland an annexe with living accommodation needs planning permission and building control approval.
In Northern Ireland building control approval comes from the council, usually through a full plans application or a building notice, with inspections during the work and a completion certificate at the end.
Our first visit includes a check of your planning history, so you know the route before paying for drawings.
What we handle
On a typical garden annexe we handle:
- Electrics and heating
- Kitchenette and shower room
- Foundations and drainage connections
- Insulated walls and roof
- Building control sign-off
- Planning drawings and application
How long does it take?
Expect 10 to 16 weeks on site. Allow time beforehand for drawings and approvals, usually 3 to 4 months.
Building in County Antrim
Northern Ireland has many detached and semi-detached homes on generous plots, which suits single-storey rear extensions and garage conversions.
Towns we cover in County Antrim include Belfast, Lisburn, Newtownabbey, Carrickfergus, Ballymena and Antrim.
How it works
- 01
Free visit
We look at the property, talk through what you want and measure up. There is no charge and no obligation.
- 02
Design and pricing
Design options, then a fixed quote based on the chosen drawings and 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 Antrim
Does it need building regulations?
Yes, as it contains sleeping accommodation and services.
Can an annexe be rented out?
Not without further planning permission, as that would make it a separate dwelling.
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.
How much does a garden annexe cost in County Antrim?
In County Antrim, a garden annexe typically costs £1,550–£2,400 per m² of floor area, including VAT at 20% (standard rate). A typical 35 m² project comes to roughly £54,000–£84,000. Your fixed price depends on the survey and drawings.
Who approves a garden annexe in County Antrim?
Planning matters in County Antrim go to the council covering your address, and the work needs building control approval. We prepare and submit the applications for you.
Do I need planning permission for a garden annexe in County Antrim?
In Northern Ireland an annexe with living accommodation needs planning permission and building control approval.