Some works to a house in Northern Ireland can be carried out without making a planning application. Those works are called permitted development. The rights are set out in the Planning (General Permitted Development) Order (Northern Ireland) 2015. They are subject to detailed limits, exceptions and conditions, and they can be restricted or removed.
Permitted development is a legal test, not a rule of thumb. If you build something that falls outside the rights, the council may later require you to put it right. nidirect advises you to check with your council planning office before you start.
What the Order covers, in broad terms
For a dwellinghouse, Part 1 of the Order covers development within the curtilage. In outline:
- Class A covers many typical extensions, with limits on ground coverage, height, rearward projection, side extensions and works facing a road. Roof alterations, basements, and decks, balconies or verandas are not permitted by this class.
- Class B covers certain roof additions and alterations, subject to limits, and it does not apply in conservation areas.
- Class C covers a porch outside an external door, subject to size, height and siting limits, including a ground area of no more than 3 square metres measured externally.
- Class D covers many outbuildings, enclosures or pools required for a purpose incidental to the enjoyment of the dwellinghouse. It does not permit development for use as a dwellinghouse.
Part 2 covers domestic microgeneration, including solar photovoltaic and solar thermal equipment on the roof or wall of a house, or of a building within its curtilage, and a single stand-alone solar array. Size, height and siting limits apply, and the equipment must be primarily for heat or energy used within the curtilage of the house.
The Order has been amended, including in May 2026. Always check the current official text, because the limits are precise and are often measured from the original dwellinghouse. These rights generally apply to dwellinghouses. nidirect states that you need planning permission to add to or extend a flat or maisonette.
Conservation areas, listed buildings and other limits
Permitted development rights are tighter, and in some cases they do not apply, in conservation areas, World Heritage Sites, Areas of Outstanding Natural Beauty and National Parks. Two-storey extensions and certain cladding are not permitted by Class A in those designated areas, and roof alterations under Class B are not permitted in a conservation area. Solar equipment on a roof or wall that faces onto and is visible from a road is also restricted in a conservation area or World Heritage Site.
If the house is listed, or the works are within its curtilage, listed building consent may be needed even where planning permission is not. Many permitted development classes do not apply unless that consent has already been granted. A condition on an earlier permission may also have limited the rights, so always check the planning history.
If the works would create a separate home, or an outbuilding would no longer be incidental to the house, permitted development is unlikely to apply. See our pages on house extensions and change of use. Building regulations are separate from planning and may still apply.
Certificates of Lawfulness
If you want a formal decision on whether a proposal, or an existing building or use, is lawful, you can apply to the council for a Certificate of Lawful Use or Development under sections 169 and 170 of the Planning Act (Northern Ireland) 2011. nidirect explains that a fee is payable. If the council is satisfied, it must issue a certificate; otherwise it must refuse. Informal opinions are not a substitute. The usual period after which enforcement action may not be taken is five years, but that is not automatic lawfulness.
How we can help
Patrick O’Reilly, Senior Planning Consultant at NI Planning Permission Ltd, is a chartered planner and a Full Corporate Member of the Irish Planning Institute (MIPI). We can review drawings against the current Order, advise whether planning permission or a certificate of lawfulness is the safer route, and prepare the planning application if one is needed. Only the council can issue a certificate.
Frequently asked questions
Can I always build a rear extension without planning permission?
No. Class A sets several limits, and designated-area rules and planning conditions can remove the right.
Are garden rooms and sheds permitted development?
Often they can be, under Class D, if they are incidental to the house and meet the limits. Use as a separate dwelling is not permitted by that class.
Do solar panels on a house need planning permission?
Often they do not, if they meet the Part 2 limits. Conservation areas, World Heritage Sites and listed buildings are different.
How do I get a definite answer?
Apply to the council for a Certificate of Lawful Use or Development, or ask us to prepare that application.
Request planning help
If you are planning an extension, outbuilding, porch or solar installation, we can help you check the position before work starts. Enquire through our contact form or call 028 9591 6888. Our free planning guides include an extension checklist.
NI Planning Permission Ltd, Scottish Provident Building, 7 Donegall Square West, Belfast BT1 6JH. Email info@niplanningpermission.co.uk.
This page is general information only. It is not a formal determination or a guarantee of any particular outcome. Check the current Order and the position with the relevant council.