Planning and building rules · Republic of Ireland

Do you need planning permission for an attic conversion?

Reviewed 29 August 2026 · General information only. Your property and your proposed design determine the answer.

Short answer: often not, but an exemption is conditional, never automatic. New exempted-development regulations took effect on 27 July 2026 and widened what can be done to a roof without permission. Whether your project qualifies depends on the exact design, your property's planning history and its location. Building Regulations apply either way.

What changed on 27 July 2026

Seven statutory instruments — S.I. 338 to 344 of 2026 — amended the Planning and Development Regulations 2001 and each came into operation on Monday 27 July 2026. The attic-specific change is in S.I. No. 344 of 2026. It inserted Class 1B for a dormer roof extension and dormer window to the side or rear of a house, and Class 1C for roof lights on the existing front roof plane of a dwelling.

In practice this means some roof alterations may now be exempt. It does not mean attic conversions are exempt in general.

The limits in the enacted instrument

Class 1B limits the combined internal volume of dormer roof extensions to 30 cubic metres, requires the dormer to be no higher than the roof ridge, and requires at least a 20-centimetre eaves setback. Class 1C permits no more than two front-roof-plane roof lights, each no larger than 100 centimetres long by 90 centimetres wide. These figures were checked directly against S.I. No. 344 of 2026 on 29 August 2026.

Planning and building compliance are different questions

This is the single most common misunderstanding. Not needing planning permission tells you nothing about whether the work is compliant.

Planning questions

Does the proposed design fall within an exempted class?
Is every condition and dimensional limit met?
Is the home a protected structure, or in an architectural conservation area?
Does an earlier permission or condition restrict further work?
Has previous development already used up an allowance?

Building Regulations questions

Can the structure safely carry the new loads?
Is the fire detection, escape and protection strategy suitable?
Do the stairs, guarding, ventilation and insulation comply?
Is the room appropriate for its intended use?
What has to be certified, and by whom?

An attic conversion usually turns a two-storey house into a three-storey one, which changes the fire-safety requirements for the whole home — not just the new room. That duty is unaffected by any planning exemption.

How to get a definite answer

Define the intended room and the proposed roof changes, in writing.
Have a suitably qualified professional review the property, its planning history and the proposal.
If the exempted-development position is uncertain, ask your local authority — a planning authority can give a formal declaration on whether a specific proposal is exempted development.
Settle the planning and building-control route before you treat any price as complete.
Ask each contractor to state their assumptions, exclusions and which professional roles are included.

Official sources

This is not planning or legal advice

Rules, property histories and designs differ. This guide cannot determine whether a specific project is exempt, notifiable or compliant. Only a suitably qualified professional or your local authority can do that for your home.