Planning guide
Garden room planning permission in Ireland: what changed in 2026
Two separate exemptions came into force on 27 July 2026, and they are constantly being confused. A garden room you work in can now be up to 30 square metres without planning permission, up from 25. A detached unit somebody actually lives in is a different exemption entirely, between 32 and 45 square metres, with conditions attached and a notice you have to give the council before anyone digs.
Which of the two you are building decides your height limit, your paperwork and, more than most people expect, what has to go in the ground.
What changed on 27 July 2026
| What you are putting in the garden | Floor area | Lived in? | Planning |
|---|---|---|---|
| Shed, store, home office, gym | Up to 30 m2 | No | Exempt, was 25 m2 before July 2026 |
| Detached auxiliary dwelling behind the house | 32 to 45 m2 | Yes | Exempt to 31 December 2030, 14 days notice to the council |
The second one is the genuinely new class. It allows a permanent detached home in the back garden, linked to the services of the main house, without a planning application. It came in under S.I. 340 of 2026 and is summarised for local authorities in Circular PLR02/2026. Anything you read online dated before late July 2026 will still say 25 square metres and will not mention the dwelling class at all, so check the date on whatever you are reading.
The two numbers people mix up
There is a maximum and there is a minimum, and they are not the same number.
- 30 square metres is a ceiling. That is the largest a non-habitable structure can be.
- 25 square metres is a floor. That is how much private open space has to be left in the garden afterwards.
Both apply at once, and in a lot of Irish gardens the open space rule bites long before the size rule does. A terraced house with a modest yard can be well inside 30 square metres and still fall outside the exemption because there is not 25 square metres of garden left over.
The floor area is also cumulative. An existing shed or a block-built garage in the corner counts towards the total, so a 12 square metre shed already in place leaves you 18, not 30.
Conditions on the 32 to 45 square metre dwelling
The habitable class is the one worth reading properly before ordering anything. In summary form:
- Floor area between 32 and 45 square metres, counted together with the relevant structures already in the garden.
- To the rear of the principal house, and at least 0.6 metres from any wall or boundary.
- Linked to the services of the main house. No separate water or utility connection of its own.
- The planning authority must be notified at least 14 days before work starts, on the form each council publishes.
- Works have to be started and completed before 31 December 2030.
- It cannot be sold separately from the house and cannot be used for short-term letting.
- Height capped at 4 metres with a tiled or slated pitched roof, 3 metres with any other roof.
- 25 square metres of private open space still has to be left in the garden.
- Building regulations apply in full, fire safety included, because this is a dwelling rather than a shed.
That last line is short and it carries most of the cost. The official summary of all seven sets of 2026 regulations is on gov.ie, and Citizens Information covers the everyday version. Take the conditions from those rather than from a brochure.
Why the label decides what goes in the ground
Two buildings can look identical in a garden and need completely different slabs underneath. This is the part that catches people out, because the supplier quotes the building and somebody else quotes the base.
A garden room nobody sleeps in, up to 30 square metres, sits on a shed base. A larger one than it used to be, but the same build: a dig out, a compacted 804 hardcore sub-base, a damp proof membrane, and a C20 concrete slab with mesh once the span justifies it. In Dublin, a standard concrete base of that type runs at roughly 100 to 150 EUR per square metre, with ground conditions and access moving the number more than size does.
A habitable unit between 32 and 45 square metres is a regulated building, and the regulations reach into the floor as much as the walls. Insulation under the slab, a continuous lapped membrane, thickness and reinforcement to the specification your supplier or engineer provides. None of that can be added later. Once the concrete has gone off, the floor build-up is fixed.
Shed Base Dublin work on both types and set the difference out in their guide to garden room bases in Dublin, including what a habitable floor spec changes about the price. Ask your supplier which of the two classes they are selling you before you get groundworks priced, because the answer changes the number.
The services have to cross the base
Here is a consequence of the no separate connection rule that rarely makes it into planning summaries.
If the unit runs off the main house, then water in, waste out and the electrics all travel from the house, across the garden, and up into the building. They cross the ground the base is sitting on.
Ducts laid before the pour cost an hour. Remembered afterwards, they cost a slab. Have that conversation with whoever is doing the groundworks before the setting out, not after.
Your base is part of your height
The height limit is measured from the ground around the structure, and a slab has a thickness. A hundred and fifty millimetres of concrete comes straight off the allowance.
On level ground with a pitched roof, nobody notices. On a garden that falls across its width, with a flat roof unit already designed to 2.9 metres, the downhill corner is where a compliant building quietly becomes a non-compliant one. Sort the finished levels before you commit to a building height.
The order that saves money
- Measure the garden and work out what open space is left after the building goes in.
- Decide whether it is habitable or not. That single answer sets your class, your limits and your floor spec.
- Get the base specification from the supplier in writing.
- Price the groundworks with that spec in hand, and settle the finished levels.
- If it is the auxiliary dwelling class, notify the council at least 14 days before work starts.
- Then book the delivery.
Most of the expensive mistakes come from running that list backwards: building bought, delivery booked, base arranged in a hurry the week before, and nobody checked the height or the ducting until it was standing there.
When to ring the council anyway
Exempted development is a general rule and general rules have edges. Ring the planning section before starting if your house is a protected structure, if you are in an architectural conservation area, if you are on a corner site or an unclear boundary, or if a previous owner already used up the allowance with something you did not know about.
Dublin City Council, Fingal, South Dublin and Dun Laoghaire-Rathdown each handle their own area and each publish the 14 day notification form. A five minute question is cheaper than an enforcement file.
If you want quotes for the groundworks, the shed base installers in Dublin shortlist is the place to start.
Frequently asked questions
Do I need planning permission for a garden room in Ireland?
Not if nobody lives in it, it stays at or under 30 square metres counted together with any similar structure already in the garden, it sits behind the building line, it respects the height limits and at least 25 square metres of private open space is left in the garden. The 30 square metre figure replaced 25 on 27 July 2026.
What is the difference between the 30 square metre and the 45 square metre exemption?
The 30 square metre exemption covers a structure nobody lives in: a shed, store, home office or gym. The 32 to 45 square metre exemption is a new class for a detached habitable dwelling in the rear garden, linked to the services of the main house, and it carries extra conditions including a 14 day notice to the council and full building regulations compliance.
Do I have to tell the council before building a garden dwelling?
Yes. For the detached auxiliary dwelling class the planning authority has to be notified at least 14 days before work starts, using the notification form the council publishes. The works also have to be started and completed before 31 December 2030. There is no notification requirement for an ordinary garden room under 30 square metres.
Does a garden room base cost more than a shed base?
For a non-habitable garden room, it is the same build at a larger size, roughly 100 to 150 EUR per square metre in Dublin for a standard concrete base. For a habitable unit the floor is built to the supplier or engineer specification, with insulation, membrane detailing and reinforcement, so it is priced against that spec rather than off a rate card.
Can a garden room sit on gravel or paving slabs instead of concrete?
Only for a small, light building, and only if the manufacturer allows it. Most garden room and log cabin suppliers specify a level concrete pad and tie their warranty to it. Above roughly 20 square metres, concrete is the practical option, and for a habitable unit it is the only one.
Rules sorted and need the ground done? Compare the shortlists (shed base installers in Dublin) and use the quote request on the hub page to hear back from up to three contractors. Related guides: Driveway cost Dublin, Patio cost Ireland, Resin vs block paving, When to call pest control, Patio installation Ireland, and the full hiring guide.