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Can I build a granny flat in my garden in Ireland?

Generally yes with planning permission, and sometimes without it if it stays within the very limited 25 m² non-habitable outbuilding exemption, but a self-contained unit with its own kitchen and bathroom used as separate living accommodation almost always needs a full planning application.

A "granny flat" — self-contained accommodation in the garden for an elderly parent, adult child or other family member, typically including its own kitchen, bathroom and living space — is generally treated as a material change of use to residential accommodation, which is not covered by the domestic outbuilding exemptions in Class 2 or 3 of Schedule 2, since those exemptions specifically exclude use for human habitation.

A planning application for a granny flat is usually assessed more favourably than an application for a fully independent second house, because local authorities recognise the social value of on-site family support, and some development plans include specific policies supporting ancillary family accommodation, sometimes with conditions restricting it to occupation by a family member and requiring its removal or reversion to a non-residential use if that arrangement ends.

Genuinely non-habitable use, such as a garden room without cooking facilities used just as extra living space during the day, can still fall within the 25 m² exemption, but as soon as full self-contained living accommodation with sleeping and cooking facilities is provided, the safer and generally required route is a full planning application.

What to include in a granny flat application

A well-prepared application will typically address:

  • The intended occupant and relationship to the main household
  • Whether the unit will be linked to the main house's services or self-contained
  • Design and scale that keeps the unit clearly ancillary to the main house, not a separate dwelling
  • Adequate private open space remaining for both the main house and the new unit
  • Parking and access arrangements
  • Any occupancy condition the local authority may wish to attach restricting future use or sale

Some local authorities are willing to grant permission subject to a condition that the unit is used only by a family member and is not sold or let separately from the main house — read any such condition carefully, since it affects the property's future flexibility.

Selling or letting later

If there is any prospect of selling the granny flat separately or letting it independently in future, discuss this with the planning authority at application stage, since occupancy conditions attached to family accommodation permissions can restrict that later use.

Sources

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

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