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 Carrickfergus?
In Carrickfergus, 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. The guide for Carrickfergus reflects typical costs in Northern Ireland, roughly 14% below the UK-wide figure. 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:
- Drainage connection distance
- Size and layout
- Heating type
- Kitchen and bathroom
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 Carrickfergus?
The approval route for Carrickfergus 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.
If the answer is not clear-cut, we can apply for formal confirmation before you commit to the build.
What we handle
The work we manage on a garden annexe:
- Planning drawings and application
- Insulated walls and roof
- Glazed doors and windows
- Electrics and heating
- Foundations and drainage connections
- External cladding or brickwork
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 Carrickfergus
Across Northern Ireland, bungalows and chalet bungalows are common, so loft conversions and rear extensions are popular projects.
Projects in Carrickfergus (BT38) are surveyed in person before we quote, so the price reflects your actual property.
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 fixed quote
Drawings, structural calculations and an itemised, fixed price for the agreed specification.
- 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 Carrickfergus
Do you build garden annexes in Carrickfergus?
Yes. We build garden annexes across Carrickfergus, including postcodes BT38. Every project starts with a free home visit.
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 Carrickfergus?
In Carrickfergus, 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.
Can an annexe be rented out?
Not without further planning permission, as that would make it a separate dwelling.
Do I need planning permission for a garden annexe in Carrickfergus?
In Northern Ireland an annexe with living accommodation needs planning permission and building control approval.
How long does it take?
Typically 10 to 16 weeks on site.