Attic conversion and dormer planning permission in Ireland

Do you need planning permission for an attic conversion?

Planning law looks at the development, not the room. Section 4(1)(h) of the Planning and Development Act 2000 exempts works that affect only the interior of a structure, or that do not materially affect its external appearance so as to make it inconsistent with the character of the structure or neighbouring structures.

In practice:

• Internal work only: floor strengthening, insulation, internal walls and stairs are generally exempt from planning.
• Dormer to the side or rear: exempt only if it meets Class 1B (see below).
• Dormer to the front: Class 1B covers the side or rear only, so a front dormer needs permission.
• Rooflights: front rooflights must meet Class 1C. Class 1C does not cover rooflights on the side or rear, so whether those need permission depends on section 4(1)(h). Ask the council.

When a dormer is exempt

From 27 July 2026, S.I. 344 of 2026 added Class 1B to Part 1 of Schedule 2 of the Planning and Development Regulations 2001. It covers a dormer roof extension and the insertion of a dormer window to the side or rear of the house.

The conditions are:

• The internal volume must not exceed 30 cubic metres. This is for the dormer on its own or together with other dormer roof extensions.
• The dormer must be no higher than the roof ridge.
• There must be an eaves setback of at least 20 centimetres.

When front rooflights are exempt

Class 1C covers the insertion of roof lights on the existing front roof plane. The conditions are:

• A maximum of two roof lights on the front roof plane.
• Each roof light must not exceed 100 centimetres in length and 90 centimetres in width.

When you need to apply

Apply for planning permission if any of these is true.

• You want a dormer on the front of the house.
• The dormer is over 30 cubic metres, higher than the ridge or too close to the eaves.
• You want more than two front rooflights, or larger ones.
• An earlier planning permission has a condition that rules out roof changes.

Article 9 of the Regulations says exempted development loses its exemption if it would break a condition of an existing permission.

Special cases

• Protected structures: under section 57 of the 2000 Act, works are exempt only if they would not materially affect the character of the structure. Roof changes often do.
• Architectural conservation areas: Article 9 removes the exemption for exterior works that would materially affect the character of the area.
• Natura 2000 and other nature sites: if the work needs an appropriate assessment, it is not exempt. Roofs can also hold bats and nesting birds. Wildlife law applies separately.
• Previously extended houses: check how your council counts a dormer alongside earlier extensions. The rules do not say how the two interact, so ask.
• Flood risk: this rarely matters for a roof change. It matters more if the attic conversion is part of a bigger project.

Attic conversions and Building Regulations

Planning exemption is not the same as building approval. The Building Regulations apply separately, including fire safety, safe stairs and structure. Many attics need new floor joists and a proper stair, and these affect how much headroom is left. Speak to an architect or engineer early.

Costs and fees

The national planning fee for works to an existing house, including a conversion, is €34. Retention permission costs more. Use the planning fee calculator for the exact figure.

Checklist before you start

• Is the dormer on the side or rear, not the front?
• Is the dormer no more than 30 cubic metres inside?
• Is it no higher than the ridge and at least 20 centimetres from the eaves?
• Are there no more than two front rooflights, each within 100 by 90 centimetres?
• Is the house free of protected structure, conservation area or nature site rules?
• Has an earlier permission put conditions on the roof?
• Have you spoken to a professional about the Building Regulations?

Next steps

Ask the council for a pre-planning meeting if the case is borderline. These meetings come from section 247 of the 2000 Act. The advice does not grant permission.

If you need to apply, see how to apply. Browse similar cases in planning applications. If the work is already done, read about retention permission. A larger project may fit a house extension.

The law is changing

The Planning and Development Act 2024 is being brought into force in stages. Class 1B and Class 1C were made in July 2026 under the 2000 Act. Check the Department of Housing’s website for which parts of the 2024 Act are in force before you start.

Check before you build

The rules depend on the exact house, the roof and the planning history. A pre-planning report checks zoning, protected structures and nature sites at an address, so you know the main limits before you pay for drawings. Use the pre-planning report or the planning permission checker. Then confirm with your council.