If you’ve been putting off converting the attic or building a granny flat for an elderly parent because the idea of planning permission felt like more hassle than it was worth, the rules are about have just changed quite significantly. Ireland’s exempted development regulations are getting their biggest update in almost 25 years, and for homeowners across Cork, that could open up options that simply weren’t on the table before. Given how quickly this is moving, it’s worth understanding exactly what’s changed and, just as importantly, what isn’t.
What’s actually changing under the new exemptions
The Department of Housing has confirmed a number of changes to exempted development regulations, meaning certain works will no longer require planning permission at all. The headline changes include:
- A new “auxiliary habitable dwelling” exemption, allowing a detached unit of between 32 and 45 square metres in a back garden, the kind of space that could suit an adult child or an elderly parent.
- A sub-division exemption, allowing a home to be split to create one additional self-contained unit, provided it’s a minimum of 32 square metres.
- Dormer roof box and roof light extensions, opening up more attic conversion options.
- An increase in the maximum size for extensions, from 40 square metres up to 45 square metres.
- Larger garden structures, with sheds, home offices and gyms increasing from 25 square metres up to 30 square metres.
For a lot of Cork homeowners sitting on older housing stock with gardens too small for a full build but big enough for something smaller, this is a meaningful shift.
When these rules come into effect
These changes are now law. The Planning and Development (Exempted Development) Regulations 2026 were signed on 16 July and came into effect on Monday 27 July 2026, so if you’re in Cork weighing up an extension, a garden room, or splitting your home into two units, these exemptions are live right now.
One important catch: the auxiliary dwelling exemption isn’t open-ended. The development has to be both started and finished between 27 July 2026 and 31 December 2030, so this is a window, not a permanent change. It’s also worth knowing that the new home can’t be sold separately from the main house, can’t be used for short-term letting like Airbnb, and at least 25 square metres of private garden has to remain once it’s built. If you’re planning a project, it’s worth confirming your specific proposal meets every condition before you assume it’s exempt, since a small detail like height or garden space left over can be the difference between exempt and not.
Why “exempt from planning” doesn’t mean “no engineer needed”
This is probably the most important point in the whole update, and it’s one that’s easy to miss. An exemption from planning permission is not the same as an exemption from Building Regulations, Building Control requirements, or Fire Regulations. All of these still apply, including for a fully habitable auxiliary dwelling in your back garden.
A 45 square metre unit still needs proper foundations, sound structural design, and correctly specified services, whether or not it needed planning permission to go ahead. Skipping planning doesn’t mean skipping the engineering. If anything, it makes it more important to get proper drawings and structural input from the outset, since there won’t be a planning process to catch anything that’s been done incorrectly.
What this means if you’re buying or selling in Cork
If you’re on the buying side of the market, this is worth keeping in mind too. An auxiliary dwelling or a subdivided unit could affect a property’s rental status, its tax treatment, and what you actually think you’re getting when you view a house. Under caveat emptor, the onus is on the buyer to identify these things before contracts are signed, not after.
This is exactly where a pre-purchase survey earns its keep. It’s not unusual for work to have been carried out under one exemption or another without ever being properly built or certified, and a thorough inspection is often the only way that comes to light before you’ve committed to buying.
What to do if you’re thinking of building under the new exemptions
If any of this has you weighing up an extension, a garden room, or splitting your home into two living spaces, the sensible first step is to check your specific project against every condition of the exemption, since size limits, garden space, and height rules all have to be met together, not just one or two of them. From there, a feasibility check will tell you what’s realistic for your site and your budget. And regardless of the planning position, don’t assume “exempt” means you can skip the professional input. Getting the structural side right from day one will save you far more hassle than it costs.
If you’re thinking about adding a garden room, converting your attic, or splitting your home into two living spaces, get in touch and we’ll help you figure out what’s actually involved before you start.
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