Home / Garden rooms in Northern Ireland

Garden rooms in Northern Ireland

Updated 22 October 2026

A pale green garden building with a chair and a cat on the lawn

The short answer: Northern Ireland has its own rules. A garden room is usually permitted development if it's no more than 4m tall, the eaves within 2m of a boundary are no higher than 2.5m, it isn't in front of any wall of the house that faces a road, and it has no deck or raised platform.¹ Rooms up to 30m² with no sleeping accommodation are often exempt from building regulations.²

Planning permission in Northern Ireland

In Northern Ireland garden buildings come under Class D of the permitted development rules. The limits:¹

No more than 4m tall, whatever the roof shape.
Eaves no higher than 2.5m within 2m of a boundary.
Not in front of a wall of the house that faces a road.
At least 3.5m from a boundary with a road behind the house.
No deck, balcony, veranda or raised platform.
Together with other buildings, covering no more than half the garden.
Not used as a home.

Flats don't have these rights at all.³ In the grounds of a listed building you need permission unless listed building consent has already been granted.¹

Protected land

In a conservation area, Area of Outstanding Natural Beauty, national park or World Heritage Site, you can't build between the front or side of the house and the boundary. In an AONB, national park or World Heritage Site, buildings more than 20m from the house can also cover no more than 10m² in total.¹ Some council guides apply the 10m² rule to conservation areas too, but the law itself doesn't.

Northern Ireland has 8 Areas of Outstanding Natural Beauty: Lagan Valley, Causeway Coast, Antrim Coast and Glens, Binevenagh, Mourne, Ring of Gullion, Sperrin, and Strangford and Lecale.⁴

Building regulations

A detached single-storey garden room with no sleeping accommodation is exempt from building regulations if it's:²

up to 15m² and at least 1m from the house, or
up to 30m² and either built mostly of non-combustible materials, or at least 1m from the house, any road and the boundary.

Note the difference from England: in Northern Ireland the 1m gap is measured from the house as well as the boundary.

Electrics

Northern Ireland has no equivalent of England's Part P for home electrical work.⁵ That makes choosing a qualified, registered electrician even more important, as nobody else will check the work.

Who to ask

Planning is shared between the 11 councils and the Department for Infrastructure.⁶ Ten councils use the NI Planning Portal; Mid Ulster has its own system.⁷ A householder application for an outbuilding was £347 from April 2025, and a certificate of lawfulness, confirming you don't need permission, is half the fee.⁸ Check your council's current fees before you apply.

What a garden room costs in Northern Ireland

We haven't found a reliable Northern Ireland price guide. Installed garden rooms typically cost £1,200 to £2,500 per m² across the UK⁹, so a 4m x 3m room usually costs £14,400 to £30,000 before extras.

Questions people ask

Do I need planning permission for a garden room in Northern Ireland?

Usually not, if it's no more than 4m tall, the eaves near a boundary are under 2.5m, it isn't in front of a wall of the house that faces a road, and it has no deck or raised platform. Flats always need permission.

Do garden rooms in Northern Ireland need building regulations?

Not if the room is single-storey, has no sleeping accommodation and is either under 15m² and 1m from the house, or under 30m² and 1m from the house, road and boundary (or built of non-combustible materials).

Who checks the electrics on a garden room in Northern Ireland?

There's no statutory scheme, so use a qualified, registered electrician and keep the certificate.

Related guides

A small dark timber building beside a lawn and blue hydrangeas

Other areasRules and costs in other parts of the UK.

A small modern garden room with glass doors at the end of a fenced garden

Free planning reportCheck protected land at your postcode.

A white timber garden building with French doors and a red roof

Garden room costsReal prices by size, with a calculator.

Sources

legislation.gov.uk, Planning (General Permitted Development) Order (NI) 2015, Part 1. Class D outbuildings.
legislation.gov.uk, Building Regulations (NI) 2012, Schedule 2. Class 7 small detached buildings.
legislation.gov.uk, Planning (General Permitted Development) Order (NI) 2015, article 2. Definitions, including flats.
DAERA, Areas of Outstanding Natural Beauty.
Which? Trusted Traders, Electrical installation regulations, updated November 2025.
Department for Infrastructure, The NI planning system.
nidirect, Planning Portal.
Armagh City, Banbridge and Craigavon Borough Council, Planning fees from 1 April 2025.
MyBuilder, Garden room cost price guide, updated 21 October 2026. UK price ranges for garden rooms, foundations, electrics, plumbing and fees.