Garden room, shed or log cabin: the size limit
A shed, garage, greenhouse, store, garden room or log cabin needs no planning permission if all such structures on the property add up to no more than 30 m² none of them is in front of the house, and the height and open space conditions below are met. Since 27 July 2026 the limit is 30 m² instead of 25 m². It cannot be lived in.
What the rule covers
This is Class 3 of the Planning and Development Regulations 2001, as replaced by S.I. No. 338 of 2026. It lists tents, awnings, shades, greenhouses, garages, stores, sheds "or other similar structure" placed within the curtilage of a house. A garden office, gym or log cabin is not named in the text; the Department's circular on the 2026 changes gives a home office and a gym as examples of a back-garden structure under this class.
The conditions
| Condition | Limit |
|---|---|
| Total floor area of all such structures, old and new | 30 m² |
| Height with a tiled or slated pitched roof | 4 m |
| Height with any other roof | 3 m |
| Private open space left at the rear or side | at least 25 m² |
Also:
- Not forward of the front wall of the house.
- At the side of the house, a garage or other structure must have the same external finishes as the house, and the same roof covering if it has a tiled or slated roof.
- Use. The structure cannot be used for human habitation, for keeping pigs, poultry, pigeons, ponies or horses, or for anything other than a purpose incidental to enjoying the house. Citizens Information sums this up as: not lived in, and not used for commercial purposes.
A log cabin to live in
A log cabin that someone lives in is human habitation, which Class 3 excludes. Since 27 July 2026 a different exemption, Class 3A, allows a permanent detached home in the back garden of 32 to 45 m², with its own conditions, including telling the council beforehand. Sheds already in the garden count towards its 45 m² ceiling. For caravans and mobile homes, see mobile homes in the garden.
Before you build
An exemption does not apply in some cases, for example if the work would break a condition of an earlier planning permission or extend an unauthorised structure (article 9 of the Planning and Development Regulations 2001). Protected structures and houses in an architectural conservation area have extra restrictions, according to Citizens Information. If your structure is over 30 m², too tall, in front of the house or meant to be lived in, you need planning permission: see the application fee and apply to your council or on planning.localgov.ie.
Other garden rules: bike and bin stores, heat pumps. All the limits are on the drawing of the house.