Ireland’s New Class 3A Exemption: What You Need to Know Before Building
Check out our 45m2 modular home!
Ireland has officially opened the door to a new era of small-scale housing flexibility. With the introduction of Class 3A under the Planning and Development (Exempted Development) Regulations 2026, homeowners can now construct a detached house in their rear garden—without planning permission—provided they meet a detailed set of rules.
This is one of the most significant changes to domestic exempted development in years, and it’s designed to support family accommodation, multigenerational living, and controlled densification, all while protecting neighbours, safety, and proper planning.
Why This Matters
Class 3A is a powerful new tool for homeowners who want to:
- Create accommodation for family members
- Support ageing in place
- Build a Self Contained living space for adult children
- Add flexible living space without navigating planning permission
But it comes with rules, and every one of the 20 points must be met to qualify.
Full List of the 20 Requirements
Below are the exact regulatory points as stated in the statutory instrument:
- For the purposes of this exemption, the relevant period begins on the date that this Regulation is signed and ends on 31 December 2030.
- This exemption shall apply only to development that is commenced and completed during the relevant period.
- The detached dwelling may only be occupied in conjunction with the main dwelling house and cannot be sold or subdivided separate to the principal dwelling.
- For the avoidance of doubt, the relevant building control legislation shall apply (such as Building Regulations (including Fire Safety) and Building Control Regulations).
- The construction of the detached house shall not be temporary in nature, such as a caravan or mobile home.
- The height of any such structure shall not exceed, in the case of a building with a tiled or slated pitched roof, 4 metres or, in any other case, 3 metres.
- The total area of such structures constructed, erected or placed within the rear garden of the curtilage of a detached house shall not be less than 32 square metres. Taken together with any other such structures previously constructed, erected or placed under Class 3 within the said curtilage, shall not exceed 45 square metres.
- This exemption shall not be used in cases where there has been a subdivision of the principal house.
- The construction, erection or placing within the curtilage of the principal house of any such structure shall not reduce the total amount of private open space reserved exclusively for the use of the occupants of the house to less than 25 square metres.
- No new vehicular or pedestrian access onto a road shall be constructed under this class.
- Independent pedestrian and/or wheelchair access to the detached house shall be provided within the curtilage of the principal house.
- There shall be no separate connection to utilities, including water or wastewater utilities, subject to paragraph 13.
- In the case of non-piped waste water treatment, the structure shall not encroach on any approved percolation area. On site waste water, treatment shall be of sufficient capacity to meet the additional loading and shall comply with the EPA Code of Practice for Domestic Waste Water Treatment Systems. There shall be no additional waste water treatment units installed as part of this class.
- The structure shall be a distance of not less than 0.6 metres from any wall or party boundary.
- Any windows proposed in the structure should be at least 0.6 metres from the boundary they face.
- Subject to paragraph 17, a notification shall be submitted to the relevant Planning Authority not less than 14 days prior to the commencement of the works informing them of the intention to use this Class of exemption, confirming that the site meets the requirements under these Regulations and stating the reason for the intended use.
- A notification under Paragraph 16 shall include the location of the proposed use of this class of exemption and the Eircode of the relevant property.
- The Planning Authority shall maintain a record of all notifications under this exemption and report annually to the Minister on the number of notifications received under this Class.
- The detached dwelling may not be used for the purposes of Short-Term Letting.
- The exemption shall only apply where the principal dwelling house is the sole or main residence of the property owner at the time the development is commenced.