# 45m2 Extension Exemption | Ireland's New Rules from July 2026 > The 45m2 extension exemption explained: rear extensions up to 45 m² without planning from 27 July 2026, how earlier extensions count, and what still applies. URL: https://structuralengineer.ie/guide/45m2-extension-exemption/ Learn # 45m2 Extension Exemption: What Changed in July 2026 Rear extensions up to 45 m² no longer need planning permission. Here's what the new limit covers, what it doesn't, and what still applies. By StructuralEngineer.ie · Reviewed by Joachim Louw, CEng MIEI · Updated 19 October 2026 [StructuralEngineer.ie](https://structuralengineer.ie/)'s summary of the change: from 27 July 2026, the 45m2 extension exemption lets you build a rear extension of up to 45 m² without planning permission, up from 40 m². The limit includes every extension built since 1 October 1964, at least 25 m² of private open space must remain, and the height and boundary conditions still apply. The change came in through the 2026 amendments to the Planning and Development (Exempted Development) Regulations (reported as S.I. 338–344 of 2026). This guide is based on published summaries. Check the statutory instrument on the Irish Statute Book, or ask your council, before relying on it for a specific house. ## What the 45 m² exemption covers - **Rear extensions only.** Side and front extensions still need permission. - **45 m² in total**, counting any extension built since 1 October 1964. - **Open space.** At least 25 m² of private open space must remain behind the house. - **Height and boundaries.** The existing conditions on height, and on walls near boundaries, still apply, and two-storey extensions have tighter conditions than single-storey ones. ## Other 2026 changes worth knowing - **Garages, sheds and garden structures.** The limit rises from 25 m² to 30 m². - **Dormers.** Side and rear dormers are newly exempt within limits, reported as about 30 m³ of volume, below the ridge and set back from the eaves. Front dormers still need permission. - **Garden units.** A new class covers a detached habitable unit of 32–45 m² in the rear garden, subject to conditions. ## When the exemption doesn’t apply - **Estate conditions.** Some estates have planning conditions that remove exempted development rights. Check the original grant for your estate. - **Protected structures and ACAs.** Works can need permission where they’d otherwise be exempt. - **Over the limit.** If earlier extensions plus the new one exceed 45 m², the whole new extension needs permission. ## What still applies: Building Regulations and BCAR The exemption is about planning only. The **Building Regulations apply in full**: structure, fire, energy, moisture and access. And the **BCAR threshold stays at 40 m²**: extensions over 40 m² need a Commencement Notice with compliance documentation, a designer and an assigned certifier, unless the owner opts out. Between 40 and 45 m², the two thresholds overlap, so confirm with your building control authority how they treat your extension before you start. ## Bottom line Rear extensions up to 45 m² in total no longer need planning, but the structure still needs designing and the certificate still matters at sale. To design and sign off yours, call [01 270 9764](tel:+35312709764). Want a fixed fee for your job? Call 01 270 9764. Callback the same working day. Fixed fee confirmed in writing before the visit. [Call 01 270 9764](tel:+35312709764) [Request a fixed quote](https://structuralengineer.ie/contact/) ## Frequently asked questions **Does the 45 m² include my existing kitchen extension?** Yes. The limit is cumulative and counts any extension built since 1 October 1964. A house with a 15 m² extension from the 1990s has 30 m² of exempt allowance left. **Can I build a side extension without planning now?** No. The exemption covers rear extensions. Side and front extensions still need planning permission. **Do I still need an engineer for an exempt extension?** Yes, in practice. The exemption removes the planning application, not the Building Regulations. The foundations, the opening into the house and the roof still have to comply with Part A, and you'll want an opinion of compliance when you sell. Sources - [Kelleher Associates: New 2026 planning exemptions regulations come into effect](https://www.kelleherassociates.ie/new-2026-planning-exemptions-regulations-come-into-effect/) - [Buildme.ie: Planning permission for extension in Ireland 2026](https://buildme.ie/planning-permission-for-extension/) - [Do I Need Planning: New planning exemptions Ireland 2026](https://www.doineedplanning.ie/planning-guides/new-planning-exemptions-ireland) - [PlanningRegister.ie: Planning permission for an extension in Ireland](https://planningregister.ie/guides/planning-permission-for-an-extension-ireland) Get a fixed engineering fee Two short steps. We call back the same working day. Prefer to talk? [Call 01 270 9764](tel:+35312709764). A live person answers during office hours. [Related service Extensions Foundations, steel and BCAR sign-off for rear and side extensions, including the new 45 m² exemption. See the service](https://structuralengineer.ie/structural-engineer-for-extensions/) Talk it through 01 270 9764 Mon–Fri 8:00–18:00 [Call now](tel:+35312709764) ### More guides - [BCAR Extension Rules: Assigned Certifier or Opt-Out Over 40m2? When the Building Control (Amendment) Regulations apply to your extension, what the certified route involves, and what opting out really means.](https://structuralengineer.ie/guide/bcar-extension-over-40m2/) - [Extension Engineer Fees in Ireland: What a Structural Engineer Charges (2026) What a structural engineer charges to design and sign off a house extension, how BCAR changes it, and what the fee should include.](https://structuralengineer.ie/guide/extension-structural-engineer-cost/) - [Attic Conversion Regulations in Ireland (2026) What it takes for an attic to be a legal habitable room: structure, headroom, fire, stairs and the July 2026 dormer exemption.](https://structuralengineer.ie/guide/attic-conversion-regulations-ireland/) - [Opinion of Compliance vs Certificate of Compliance: The Difference One is a professional opinion, the other a statutory certificate. Which one your works have, and what your buyer's solicitor will accept.](https://structuralengineer.ie/guide/opinion-of-compliance-vs-certificate-of-compliance/)