A granny flat without planning permission in Ireland: Class 3A
From 27 July 2026 until 31 December 2030 you can build a detached home of 32 to 45 m² in the rear garden of your house without planning permission, if you notify the council at least 14 days before work starts and meet every condition of Class 3A: lived in with the main house, never sold or let short-term, served through the main house’s connections and kept 0.6 m from walls and party boundaries.
Rules as of 10 October 2026. Class 3A, inserted by S.I. No. 340 of 2026, in force since 27 July 2026.
- Between 32 m² and 45 m², counting any Class 3 sheds or garden rooms already there (condition 7).
- 4 m high with a tiled or slated pitched roof, 3 m otherwise (condition 6).
- At least 0.6 m from any wall or party boundary, and windows 0.6 m from the boundary they face (conditions 14, 15).
- Notice to the council at least 14 days before work starts, with the Eircode (conditions 16, 17).
- Works started and finished between 16 July 2026 and 31 December 2030 (conditions 1, 2).
Every condition of Class 3A
| The rule | Where it is in the law |
|---|---|
| The detached house must be in the rear garden of the principal house. | Regulations 2001, Class 3A, column 1 |
| Works must start and finish between 16 July 2026 and 31 December 2030. | Regulations 2001, Class 3A, conditions 1 and 2 |
| It may only be occupied with the main house and cannot be sold or subdivided separately. | Regulations 2001, Class 3A, condition 3 |
| It must not be temporary, such as a caravan or mobile home. | Regulations 2001, Class 3A, condition 5 |
| Height must not exceed 4 m with a tiled or slated pitched roof, or 3 m in any other case. | Regulations 2001, Class 3A, condition 6 |
| It must be at least 32 m², and together with the Class 3 structures already in the curtilage must not exceed 45 m². | Regulations 2001, Class 3A, condition 7 |
| It cannot be used where the principal house has been subdivided. | Regulations 2001, Class 3A, condition 8 |
| At least 25 m² of private open space must remain. | Regulations 2001, Class 3A, condition 9 |
| No new vehicle or pedestrian access onto a road; independent pedestrian or wheelchair access to it within the curtilage. | Regulations 2001, Class 3A, conditions 10 and 11 |
| No separate connection to utilities, including water and wastewater. | Regulations 2001, Class 3A, condition 12 |
| With a septic tank or other non-piped treatment: no building on an approved percolation area, enough treatment capacity under the EPA Code of Practice, and no additional treatment unit. | Regulations 2001, Class 3A, condition 13 |
| At least 0.6 m from any wall or party boundary. | Regulations 2001, Class 3A, condition 14 |
| Windows at least 0.6 m from the boundary they face. | Regulations 2001, Class 3A, condition 15 |
| Notify the planning authority at least 14 days before work starts, with the location and Eircode, confirming the site meets the requirements and stating the reason for the intended use. | Regulations 2001, Class 3A, conditions 16 and 17 |
| It must not be used for short-term letting. | Regulations 2001, Class 3A, condition 19 |
| The principal house must be the owner’s sole or main residence when work starts. | Regulations 2001, Class 3A, condition 20 |
The 14-day notice
Circular PLR 02/2026 gives councils a suggested notification template (Appendix I). Councils publish their own forms based on it. It asks for the location and Eircode, the dates, the class being notified, whether the site and development meet all the requirements, and the reason for the intended use, with a checklist of the conditions to tick.
Pro fills in that content from your project, with each tick matched to the check, ready to copy onto your council’s form.
Building control applies as for any new home
An exemption from planning permission is not an exemption from the Building Regulations. A detached auxiliary dwelling must comply as a new dwelling, with a commencement notice and the normal certification (Class 3A, condition 4; South Dublin County Council’s note on auxiliary dwellings sets out the process).
Questions
How big can a granny flat be without planning permission in Ireland?
Between 32 m² and 45 m², and the 45 m² includes any sheds or garden rooms already built under Class 3. It can be 4 m high with a tiled or slated pitched roof, 3 m otherwise.
Can I let the garden house?
Not for short-term letting (condition 19), and it may only be occupied in conjunction with the main house, which cannot be sold or subdivided separately from it (condition 3). The main house must be the owner’s sole or main residence when work starts (condition 20).
What happens after 31 December 2030?
The class only covers works started and completed between 16 July 2026 and 31 December 2030. A garden house built after that would need planning permission unless the rules are extended.
Related
- England and IrelandCheck your project in 3DThe free checker, condition by condition.
- IrelandThe new exemptions of 27 July 2026Every class that changed, old and new limits.
- IrelandShed or garden room: 30 m²Height, position and use.
- IrelandExtensions: the 45 m² ruleAbove-ground limits, 2 m and 8 m, open space.
- IrelandSection 5 declarations€80, 4 weeks, what to send.
Sources: S.I. No. 340 of 2026; Circular PLR 02/2026, Appendix I; South Dublin County Council, building control note. Last checked 10 October 2026. Irish Statute Book content is used under the Oireachtas (Open Data) PSI Licence, which incorporates CC BY 4.0. This page is not legal advice and not a formal decision; it is not affiliated with any council or government department.