Free tool
Do I need planning permission?
Ireland's exemption rules were rewritten on 27 July 2026: rear extensions are now exempt to 45 m², and a detached garden dwelling of 32 to 45 m² can be built without permission for the first time. Answer a few questions and get a verdict grounded in the regulations, with the exact class and statutory instrument cited.
Guidance, not legal advice. Every exemption carries detailed conditions; confirm with your local authority (or a Section 5 declaration) before building.
What changed on 27 July 2026
The first major rewrite of Ireland's exempted development rules in 25 years (S.I. No. 338 of 2026 and its companion instruments, signed 16 July 2026) came into operation on 27 July 2026:
- Rear extensions: the exempt limit rose from 40 m² to 45 m², still cumulative across every extension built since 1 October 1964.
- Garden rooms and sheds: the cumulative limit rose from 25 m² to 30 m², habitation still barred.
- A brand-new Class 3A: a detached habitable garden dwelling of 32 to 45 m², subject to strict conditions including a 14-day prior notification to the council, no separate sale or letting, and completion by 31 December 2030.
- New exemptions for side and rear dormers, front rooflights, and subdividing a house into two units.
Every exemption carries conditions, protected structures and conservation areas can lose them case by case, and building regulations always apply. The guides behind this checker cover the detail: extensions, garden rooms and granny flats.