Your Garden Room Just Got Bigger. It Is 30 Square Metres, Not 45

A timber garden building. Photo: Angelina Kusznirewicz / Unsplash.

On 27 July, Ireland’s planning exemptions changed for the first time in about twenty-five years. If you want a garden room, the size you are allowed to build without permission went up.

It went up to 30 square metres. Not 45. The distinction matters, and it has already been reported wrongly.

The number that is being got wrong

An Irish Times special report in April stated the detached garden structure limit was rising from 25 to 45 square metres. That conflates two entirely separate measures, and it contradicts both gov.ie and Citizens Information.

Garden structures: 30 square metres. The 45 figure belongs to the new auxiliary dwelling exemption, and to the rear extension of the main house. If you brief a builder on 45 for a garden office, you are briefing them into a planning application.

The conditions, in full

Office yes, bedroom no

This is the crucial distinction and it is where most of the confusion sits. The 30 square metre exemption is for a non-habitable structure. A home office, a gym, a studio, a workshop — all fine. Sleeping in it is not.

If you want detached accommodation somebody can actually live in, that is the separate new auxiliary dwelling exemption at 32 to 45 square metres, and Building Regulations, Building Control and Fire Regulations all apply to it. It is a house, and it is treated like one.

What else came in

The same package created exemptions that did not exist before: subdividing an existing building into up to one additional self-contained unit of at least 32 sqm; a dormer or roof box to the side or rear up to 30 cubic metres; external wall insulation, aligned with the SEAI grants, to a maximum of 15cm thick, matching existing finishes and not extending onto a public road; and cycle and bin storage front and back.

A review is scheduled eighteen months after implementation.

One honest caveat about the market

You will read that the Irish garden room market is booming. We could not find independent Irish data to support a number — searches return vendor marketing and global market-research reports with no Irish breakdown.

What is on the record is company-level and self-reported: John Sherry, managing director of Garden Rooms, told The Irish Times his company has 23 years in the Irish market and more than 2,000 bespoke commissions, and called the exemption change “a complete game changer”. Treat that as a company describing itself, not as market fact. On outdoor kitchens in Ireland we found no verifiable data at all.

And if the house is protected

None of the above is safe to assume if your house is a Protected Structure or sits in an Architectural Conservation Area. The circular accompanying the new regulations does not address how the July exemptions interact with either. Ask your local authority for a Section 57 declaration — it is free, and they must answer within twelve weeks.