House extension planning permission in Ireland

Do you need planning permission for a house extension?

It depends on where the extension goes, how big it is and what your site is like.

• Rear extension within the limits: no permission needed.
• Side or front extension: permission is generally needed, because the exemption covers the rear.
• Rear extension outside the limits: permission needed.
• Protected structure, architectural conservation area or Natura 2000 site: extra rules apply (see below).

Apartments are not covered. The Regulations say a building with two or more dwellings, or a flat or apartment in it, is not a “house” for this exemption.

When an extension is exempt

The exemption is Class 1 in Part 1 of Schedule 2 to the Planning and Development Regulations 2001. S.I. 338 of 2026 changed it from 27 July 2026. It covers an extension, including a conservatory, to the rear of a house. These are the main conditions.

Floor area

• House not extended before: up to 45 square metres.
• Above ground level, terraced or semi-detached house: up to 12 square metres.
• Above ground level, detached house: up to 20 square metres.
• House already extended: the new extension plus any extension built after 1 October 1964 must stay within the same limits. This includes extensions that had planning permission.

Position, height and garden

• Any part above ground floor must be at least 2 metres from any party boundary.
• Walls cannot be higher than the rear wall of the house. If the rear wall has a gable, they cannot be higher than the side walls.
• A flat roof cannot be higher than the eaves or parapet. Any other roof cannot be higher than the highest part of the roof of the house.
• The extension cannot leave less than 25 square metres of private open space within the curtilage of the house, reserved for the people living there.

Windows and roof

• Ground-level windows must be at least 1 metre from the boundary they face.
• Windows above ground level must be at least 8 metres from the boundary they face.
• If the house is detached and the part above ground is over 12 square metres, the 8 metre rule also applies to those windows.
• The roof cannot be used as a balcony or terrace.
• The exemption applies to the main house only, not to another detached house in the same grounds.

When you need to apply

Apply for permission if any of these is true.

• The extension goes to the side or front of the house.
• It is larger or taller than Class 1 allows.
• It would leave less than 25 square metres of private garden.
• A condition on an earlier planning permission rules it out. Article 9 of the Regulations removes the exemption if the work would break a condition of an existing permission.
• The house or the structure being extended is unauthorised.
• It would harm a view or landscape that the development plan protects.

Special cases

• Protected structures: under section 57 of the 2000 Act, works are exempt only if they do not materially affect the character of the structure. Owners can ask the council for a declaration.
• 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: the exemption does not apply where an appropriate assessment is needed, because the work could have a significant effect on a European site.
• Flood risk: Article 9 does not list flood risk as a reason to lose the exemption. Councils do look at flood risk in applications, so check the council’s flood maps before you design.

Costs and fees

The national fee for a planning application for a house extension is €34. Retention permission costs more. Use the planning fee calculator to work out the exact amount. Drawings, a site map and a professional’s time are separate costs.

What counts against you

Councils often raise the same points.

• Loss of light or privacy for neighbours.
• Size and height compared with the original house.
• Too little garden left.
• Materials that clash with the house and street.

Checklist before you decide

• Is the extension at the rear?
• Is it within the floor area limits, counting earlier extensions after 1 October 1964?
• Is anything above ground at least 2 metres from the party boundary?
• Will 25 square metres of private garden remain?
• Are windows far enough from the boundary?
• Is the house free of protected structure, conservation area or nature site rules?
• Did an earlier permission put conditions on the house?

Next steps

Book a pre-planning meeting with the council. These meetings are offered under section 247 of the 2000 Act. Some councils, such as Dún Laoghaire-Rathdown, describe the service as free. The advice does not grant permission.

If you need to apply, read how to apply. You can also browse nearby planning applications. If the extension already exists without permission, see retention permission. Related guides cover an attic conversion and a garage conversion.

The law is changing

The Planning and Development Act 2024 is being brought into force in stages, so some rules will change. The July 2026 exemptions amend the 2001 Regulations under the 2000 Act. Check the Department of Housing’s website for which parts of the 2024 Act are in force.

Check before you build

The rules depend on the exact site, the house and its planning history. A pre-planning report checks zoning, protected structures and nature sites at an address, so you can see the main constraints before you pay for drawings. Use the pre-planning report or the planning permission checker to start. Always confirm the result with your council.