Garden Homes & Granny Flats – the new 45 m² exemption
Since 27 July 2026, homeowners can build a detached home of up to 45 m² in the rear garden of their house without planning permission, under the new Class 3A exemption (S.I. No. 340 of 2026). It is ideal for an elderly parent, an adult child, or extended family who want to live close by.
We design garden homes that meet every condition of the exemption and the Building Regulations, so you can build with confidence.
The key conditions
- Floor area of up to 45 m² (including any other sheds or garden rooms covered by Class 3).
- Maximum height of 4 m with a tiled or slated pitched roof, or 3 m in any other case.
- At least 0.6 m from any boundary, and windows at least 0.6 m from the boundary they face.
- At least 25 m² of private garden must remain for the main house.
- The house must be your sole or main residence when works begin.
- It cannot be sold or let separately, or used for short-term letting.
- No new entrance onto the road and no separate water, wastewater or other utility connections.
- Where you have a septic tank or treatment system, it must have capacity for the extra load and the new building must not encroach on the percolation area.
- The Local Authority must be notified at least 14 days before works start.
- Works must be started and completed by 31 December 2030.
This is a summary only. Each site must be checked against the full Regulations; where a proposal does not meet the conditions, a planning application will be required, and we can prepare it for you.
How we help
- Site check – we confirm whether your garden, boundaries, open space and wastewater arrangements qualify for the exemption.
- Design and drawings – a layout that makes the most of 45 m², with full architectural and construction drawings.
- Building Regulations and structural design – fire safety, accessibility, energy performance and structure, designed and specified for your builder to price and build from.
- Notification – we prepare the 14-day notification to the Local Authority, including the site location and Eircode.
- Inspections and sign-off – site inspections during construction and certification on completion.
If your site does not qualify, we can prepare a full planning application instead.
Get a quotation
Call or email us today for a quotation. Send us your address or Eircode and a short description of what you have in mind, and we will advise whether the exemption is likely to apply and provide a quotation for the design and drawings.
Call or email us today for a quotation:
Cork: +353 (0)21 427 9229
Dublin: +353 (0)87 638 5778
Email: contact@phice.ie