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How close can an extension be to my neighbour in Ireland?

There is no single fixed distance; it depends on the height and type of the extension under Class 1 of Schedule 2 to the Planning and Development Regulations 2001, and on separate development plan standards for daylight and privacy that apply once planning permission is needed.

Irish planning law does not set one universal minimum distance between an extension and a neighbour's boundary or house. Instead, the distance is controlled indirectly through a combination of rules. Under exempted development, Class 1 of Schedule 2 to the Planning and Development Regulations 2001 limits the height of an extension close to a boundary, meaning an extension can generally come closer to the boundary only if it stays low, while taller or two-storey elements must be set back further to remain exempt.

Where a proposal needs full planning permission — because it exceeds the exemption limits or the applicant chooses to apply anyway — the local authority assesses the distance to neighbouring boundaries and windows against standards in its own development plan and against general planning guidance on daylight, sunlight and overlooking. Many development plans reference a '45-degree' or '25-degree' daylight rule of thumb to assess whether a proposed extension would unacceptably reduce light to a neighbouring window, and case officers also assess whether new windows in the extension would directly overlook neighbouring private open space or habitable rooms.

In practice, the closer an extension gets to a shared boundary, the more likely it is to need planning permission rather than relying on the exemption, and the more scrutiny it receives on daylight and privacy grounds during that application. Even where a design meets the technical planning limits, keeping some distance from the boundary and avoiding new windows facing directly into a neighbour's garden reduces the risk of an objection or a later access-for-maintenance dispute.

Factors that determine an acceptable distance

The distance that is acceptable in practice depends on:

  • The height of the extension at the point closest to the boundary
  • Whether the extension is single-storey or includes an upper floor
  • The presence and orientation of habitable-room windows in the extension and in the neighbouring house
  • The local authority's daylight and sunlight standards in its development plan
  • Whether the extension would overlook the neighbour's private open space
  • Existing site levels and any change in ground level near the boundary
  • Whether the exemption under Class 1 applies or full planning permission is required

Because these factors interact, the same extension design can be acceptable on one site and unacceptable on another purely due to boundary geometry and orientation.

Getting professional input

An architect or planning consultant can run a daylight and sunlight check against your local authority's specific standards before you finalise a design, and can advise whether your proposal is likely to remain within the exempted development limits or should be submitted as a full planning application. This is particularly worthwhile on narrow or overlooked sites.

Sources

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

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