SiteRep

Can I build an extension up to my boundary in Ireland?

Not usually as exempted development. Class 1 of Schedule 2 to the Planning and Development Regulations 2001 sets minimum distances between an extension and the boundary, and building right up to the boundary line will normally require planning permission unless a specific condition of the class allows it.

Building an extension right up to a boundary is not straightforward under Irish exempted development rules. Class 1 of Schedule 2 to the Planning and Development Regulations 2001 sets height limits that reduce as an extension gets closer to the boundary with an adjoining property, and in many cases a two-storey extension or one above a certain height must be set back a minimum distance from the boundary to qualify as exempt at all.

For a single-storey extension, the regulations generally allow a somewhat closer relationship to the boundary provided the height stays low, but there are still limits, and where a wall of the extension sits directly on the boundary line, the height of that wall close to the boundary is restricted more tightly than the overall extension height. Attaching a new extension directly to a boundary wall or building a party wall arrangement can also raise separate legal issues under the law of party structures, distinct from planning law.

If your design genuinely needs to go right up to the boundary — for example to match an existing terrace configuration or to maximise a narrow site — this is the kind of proposal that often falls outside the exemption and needs a full planning application, where the local authority and, if relevant, the affected neighbour can assess the impact on light, privacy and structural matters properly.

What to check before building close to a boundary

Work through these points with your designer before finalising drawings:

  • Confirm the exact height limit that applies at the point closest to the boundary under Class 1
  • Check whether a two-storey element requires a minimum setback distance
  • Establish the true position of the boundary using the title documents and, if needed, a surveyor
  • Consider whether building on or against a boundary wall raises separate legal issues with your neighbour
  • Check local development plan policies on side-boundary setbacks, which can be stricter than the exemption
  • If exceeding any limit, plan for a full planning application rather than proceeding under the exemption
  • Talk to the affected neighbour early, even where the works are legally exempt

Boundary-adjacent extensions are one of the most common sources of neighbour disputes, so getting the planning position right from the outset is worthwhile even where it means submitting a full application.

When to apply for planning permission

If your extension design cannot meet the boundary-distance and height conditions in Class 1, you should apply for planning permission rather than assume the works are exempt. This also gives your neighbour a formal opportunity to make observations during the public consultation period, which can reduce the risk of a later dispute or complaint.

Sources

Last reviewed 20 August 2026. General information only — not legal or planning advice.

Related questions

← Back to all questions