Everything we offer for a granny flat, and the answers to the questions people ask most.
The offer
Since 27 July 2026 you can build a granny flat in your back garden without planning permission. It must be 32 to 45 m². This is the new Class 3A exemption.
You do not need planning permission. But you must do two things before work starts. First, tell your planning authority at least 14 days before you begin. Second, lodge a commencement notice. A commencement notice needs full BCAR construction drawings, so the drawings come first.
The flat fee is €6,000, all in one, from the first design to the final sign off. It is one pack, delivered together with my partner Ectiva Engineering, and the fee covers both of our roles.
My role as the architect: I design the granny flat, prepare the full BCAR construction drawings and any specification needed, and take it up to the commencement notice.
Ectiva Engineering’s role as the engineer: they advise on the structure while the drawings are prepared, then act as your assigned certifier. They carry out the site inspections, handle the paperwork, and sign it off at the end.
The assigned certifier role is already filled, so there is no one else for you to find.
Before all that, a site visit or survey checks your site qualifies. Then a builder can price and build it. We also advise on connecting to your existing services and drainage.
If your flat does not qualify, the planning or construction package in the quote calculator applies instead.
Correct, if you meet every condition. Miss one and you need planning permission. The rule is called Class 3A. It started in July 2026.
How big can it be?
At least 32 m². At most 45 m². Sheds and extensions already in the back garden under the older Class 3 rule count towards the 45 m².
How high can it be?
4 metres with a tiled or slated pitched roof. 3 metres with any other roof, such as a flat roof.
Is it only for family members?
No. The person living there does not have to be a relative. It must be lived in together with the main house. It cannot be sold on its own. It cannot be a short term let.
Can I rent it out?
Not as a separate home. It cannot be sold or split off from the house. Holiday lets are banned. If you have another use in mind, check first.
Does it still have to meet the Building Regulations?
Yes. Fire safety included. It is built like any new home. A caravan or mobile home does not count.
Do I have to tell anyone before I build?
Yes. Tell your planning authority at least 14 days before work starts. Say you are using the exemption. Give the address and Eircode. You must also lodge a commencement notice before you start. Construction cannot begin until it has been lodged.
What else does the building control process need?
Besides the commencement notice, the building control process (BCAR) usually brings other certificates and tests, depending on the project. A new home normally needs a BER energy rating, with a provisional one at design stage and the final one when it is finished. It also needs an air tightness test on the finished building and a commissioning check on the ventilation. If the site has a septic tank or its own treatment system, the system must be suitable for the extra use, and a site assessment may be needed. Finally, your assigned certifier lodges a certificate of compliance on completion. I can tell you which apply to your site.
How close to the boundary can it be?
At least 0.6 metres from any wall or boundary. Windows must also be 0.6 metres from the boundary they face.
How much garden do I have to keep?
At least 25 m² of private garden for the people in the main house.
Can it have its own water, drainage and entrance?
No separate water or wastewater connection. No new entrance onto the road. It does need its own pedestrian and wheelchair access inside your grounds. On a septic tank, the flat cannot sit on the percolation area. The tank must cope with the extra load. No extra treatment unit is allowed.
Which houses qualify?
The main house must be your own home when work starts. A house that has been split into separate units does not qualify.
Is there a deadline?
Yes. The work must start and finish by 31 December 2030.
What is the €6,000 flat fee for?
The design and full BCAR construction drawings from me as the architect, and the structural advice, site inspections and final sign off from Ectiva Engineering as your assigned certifier. See the offer above. It does not cover the build or any authority fees.
This is a short summary, not legal advice. The rule is S.I. 340 of 2026 (official text, Irish Statute Book). It has 20 conditions and you must meet every one. Tell me about your site and I will confirm if it qualifies.