Kitchen extension planning permission: the 45 m² rule
No planning permission is needed for a rear extension of up to 45 m², counting any earlier extensions built since 1964, if it meets the conditions: no higher than the house, at least 25 m² of private open space left, ground-floor windows at least 1 m from the boundary they face, and upstairs no more than 12 m² on a semi or terrace (20 m² detached). The limit rose from 40 m² on 27 July 2026.
What you can build without permission since 27 July 2026, what takes the exemption away, and how to apply if you need to.
Free, no obligation. One local builder prices it, not five.
- 45 m²rear extension without permission (was 40 m²)
- 25 m²of garden that must be left
- €34council fee to apply for a house extension
- 8 weeksfor the council's decision
Exempt if it meets all eight
The rules are Class 1 of the exempted development regulations, as replaced by S.I. No. 338 of 2026 from 27 July 2026. An extension is exempt if it meets every one of these:
- At the back. Class 1 covers an extension to the rear of the house, or turning an attached garage or shed at the back or side into part of the house.
- 45 m² in total. Counting every extension built since 1 October 1964, including any that got planning permission. It was 40 m² until 27 July 2026.
- Upstairs, less. No more than 12 m² above ground floor on a semi-detached or terraced house, 20 m² on a detached house, and at least 2 m from any party boundary.
- No higher than the house. The walls no higher than the back wall of the house (or its side walls, if the back has a gable). A flat roof no higher than the eaves or parapet; any other roof no higher than the top of the house roof.
- 25 m² of garden left. The extension can't cut the private open space of the house to less than 25 m².
- Windows back from the boundary. Ground-floor windows at least 1 m from the boundary they face; upstairs windows at least 8 m (it was 11 m).
- No roof terrace. The roof of the extension can't be used as a balcony or terrace.
- The main house only. Not a second house in the same garden.
When the exemption doesn't apply
The exemption doesn't apply if the house's own planning permission has a condition that takes exempted development away (common on newer estates), if the house is a protected structure and the work would affect its character, or if the extension would obstruct a public right of way or a road. If you're not sure, ask the council for a section 5 declaration. It costs €80 and the answer is in writing.
Check the original planning permission for your house first. The council's planning search has it, and newer estates often carry a condition that says any extension needs permission.
A side extension isn't Class 1 at all unless it's the conversion of a garage or shed that's already attached at the side. A side return is at the back of the house, but if any part of it comes forward of the back wall of the main house, get a section 5 declaration before you build. Side return extensions.
If you need planning permission
- Drawings and notices. Your designer draws the plans, and you put a notice in a local newspaper and a site notice on the house within two weeks before you apply.
- Apply to the council. The fee for a house extension is €34.
- The decision. The council has 8 weeks, longer if it asks for more information. Neighbours can comment in the first 5 weeks.
- The appeal period. Anyone who commented can appeal to An Coimisiún Pleanála within 4 weeks of the decision. Final permission issues after that.
So allow about 12 weeks from applying to final permission, if nobody appeals. The estimator below adds it to your timeline when your extension needs it.
Exempt from planning isn't exempt from the building regulations
Every extension has to meet the building regulations, exempt or not. Since 27 July 2026, an extension of up to 45 m² that is exempt from planning needs no commencement notice (S.I. No. 359 of 2026). Over 45 m², the commencement notice comes with a design certifier and an assigned certifier, or an owner's opt-out. Building regulations for extensions.
Plan your extension and see the cost
Nine quick taps. You see your plan build up as you go: the price range, what moves it, the planning position and the build time. Your number is only asked for at the end, if you want a real price.
A 25 m² single-storey rear extension in Ireland, mid-range, with wide glass doors and a new kitchen: €62,000 to €90,000 all in, including VAT and fees.
How this is worked out
We start from what single-storey extensions cost to build per square metre in each part of Ireland, including VAT at 13.5%, and the rates for side, wraparound, two-storey and heavily glazed extensions. Standard finishes take the lower half of the range, mid-range the upper half, and high spec or a wall of glass the glazed rate. Then we add professional fees (design, engineer, BER) and, if you want one, a new kitchen at your level of finish. Totals are rounded to the nearest €1,000. It's an estimate to plan with, never a quote: the builder prices your house after seeing it.
Questions people ask
How big can a kitchen extension be without planning permission?
45 m² at the back, counting every extension built since 1964, if it meets the other conditions. It was 40 m² until 27 July 2026.
Does the 45 m² include my old extension?
Yes. Any extension built after 1 October 1964 counts towards the 45 m², including ones that got planning permission.
Can I build a two-storey extension without planning permission?
Only a small one. Upstairs the limit is 12 m² on a semi or terrace and 20 m² detached, at least 2 m from the party boundary, with upstairs windows 8 m from the boundary they face.
Can I put a flat roof terrace on my extension?
Not under the exemption. The roof can't be used as a balcony or terrace.
What is a section 5 declaration?
A written answer from the council on whether your extension is exempted development. It costs €80. Worth it if you're near a limit or your estate has conditions.
Do I need to tell my neighbours?
Not for an exempt extension, though it's good manners. If you apply for permission, the newspaper and site notices tell them, and they can comment.
What if I build without permission when I needed it?
The council can take enforcement action, and it shows up when you sell: the buyer's solicitor asks for proof the extension is exempt or has permission.
Get a free quote for your extension
Plan it in under a minute, see the cost, and one vetted builder who covers your county rings you with a proper price.