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 Lisburn?
In Lisburn, 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. Building costs in Northern Ireland run about 14% below the UK average, and the figures for Lisburn are adjusted to reflect that. 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 biggest cost drivers are:
- Cladding and finishes
- Drainage connection distance
- Size and layout
- 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 Lisburn?
Here is how the rules work for a garden annexe 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.
At the survey we check your house’s planning history and any restrictions, and tell you which route applies.
What we handle
From survey to sign-off, the job normally involves:
- Kitchenette and shower room
- Planning drawings and application
- Insulated walls and roof
- Foundations and drainage connections
- External cladding or brickwork
- Electrics and heating
How long does it take?
Build time is typically 10 to 16 weeks on site. Allow time beforehand for drawings and approvals, usually 3 to 4 months.
Building in Lisburn
Across Northern Ireland, bungalows and chalet bungalows are common, so loft conversions and rear extensions are popular projects.
From BT27 outwards, we take on projects throughout Lisburn and the surrounding parts of County 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
Approvals in place
We handle planning, building control and neighbour notices before work starts.
- 04
Build and sign-off
We run the build to a written programme and hand over the completion certificate.
Questions about garden annexes in Lisburn
Do you build garden annexes in Lisburn?
Yes. We build garden annexes across Lisburn, including postcodes BT27 and BT28. Every project starts with a free home visit.
How much does a garden annexe cost in Lisburn?
In Lisburn, 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.
Do I need planning permission for a garden annexe in Lisburn?
In Northern Ireland an annexe with living accommodation needs planning permission and building control approval.
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.