45 m² Planning Exemption Ireland: Homes Without Planning Permission

The new 45 m² planning exemption in Ireland can allow a permanent detached house to be constructed, erected or placed in the rear garden of a principal house without a conventional planning application. It is a useful route for qualifying families, but it is not an automatic permission: every condition in Class 3A must be satisfied and the property should be checked before work begins.

What size home can qualify?

A Class 3A detached dwelling must provide at least 32 m² of floor area. The combined area of the new dwelling and structures previously provided under Class 3 within the same curtilage must not exceed 45 m². The maximum height is 4 metres for a tiled or slated pitched roof, or 3 metres for any other roof type.

The exemption applies only to qualifying development commenced and completed during the relevant period, which currently ends on 31 December 2030. The structure must be permanent rather than a caravan or mobile home.

Important site and access conditions

• At least 25 m² of private open space must remain exclusively for the occupants of the principal house.
• The detached house must be at least 0.6 metres from every wall or party boundary.
• Proposed windows should be at least 0.6 metres from the boundary they face.
• No new pedestrian or vehicle entrance onto a road may be created under this exemption.
• Independent pedestrian and, where needed, wheelchair access must be available within the curtilage of the principal house.
• The exemption cannot be used where the principal house has already been subdivided.

Ownership, occupation and services

The detached dwelling may only be occupied in conjunction with the main house. It cannot be sold or subdivided separately and cannot be used for short-term letting. When development starts, the principal dwelling must be the property owner’s sole or main residence.

A separate connection to utilities, including water or wastewater services, is not permitted under Class 3A. Where a property uses on-site wastewater treatment, the new house cannot encroach on an approved percolation area. The existing treatment system must have enough capacity for the additional loading and comply with the relevant EPA code; an additional wastewater treatment unit cannot be installed under this exemption.

Notification and Building Regulations

The owner must notify the relevant planning authority at least 14 days before work starts. The notification must identify the property and its Eircode, confirm that the site meets the regulations, and state the reason for the intended use. This planning notification is separate from any Building Control requirements.

Planning-exempt does not mean regulation-exempt. Building Regulations and Building Control legislation still apply, including requirements for structure, fire safety, ventilation, energy performance, drainage and professional certification. A Commencement Notice will normally be required before construction starts, subject to professional advice for the particular project.

Why an early site check matters

An early review can identify boundary, access, open-space and service issues before drawings or manufacturing begin. It can also help the homeowner understand which professional reports, notices and certifications may be required. That preparation reduces avoidable delay and ensures the proposed home, base and utility route are considered together from the outset.

Check your property before you build

Because the 45 m² planning exemption Ireland rules depend on the house, garden, boundaries, access, services and proposed use, each property needs a site-specific assessment. A-Rated Houses supplies permanent, energy-efficient steel-frame homes designed with regulatory compliance in mind, but the property owner remains responsible for confirming that the exemption applies.

Read our 45 m² house guide for a practical overview, or contact A-Rated Houses to check whether your back garden may be suitable.

This information is a general guide and is not legal or planning advice. Always obtain appropriate professional advice for your property.

Read S.I. No. 340/2026 on the Irish Statute Book