# Extension Engineer Fees Ireland | 2026 Structural Design Costs > Extension engineer fees in Ireland in 2026: €1,200–€2,200 for single-storey, €2,000–€3,500 for two-storey, plus BCAR costs over 40 m². What's included. URL: https://structuralengineer.ie/guide/extension-structural-engineer-cost/ Cost Guide # 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. By StructuralEngineer.ie · Reviewed by Joachim Louw, CEng MIEI · Updated 19 October 2026 [StructuralEngineer.ie](https://structuralengineer.ie/)'s summary of published 2026 Irish cost guides: extension engineer fees are typically **€1,200–€2,200** for a single-storey rear extension and **€2,000–€3,500** for a two-storey or wraparound extension. Complex jobs with site investigation can reach €5,000. BCAR certification over 40 m² is usually priced on top. The engineer’s fee is a small part of an extension budget. Published 2026 figures put building costs at roughly €1,900–€3,400 per m². But the design decides how much concrete and steel the builder puts in, and whether the extension can be certified when you sell. ## Typical fees at a glance | Extension | Typical engineering fee | | --- | --- | | Single-storey rear | €1,200–€2,200 | | Single-storey, larger or with wide glazing | €1,500–€3,000 | | Two-storey or wraparound | €2,000–€3,500 | | Complex, with site investigation | €2,500–€5,000 | | BCAR designer and assigned certifier (over 40 m²) | Priced separately | ## What the fee should include - Site visit to check the ground, drains, trees and the rear wall - Foundation design to I.S. EN 1997-1 - Steel for the opening into the house: beam, posts or goalpost - Roof and floor structure, rooflight trimming - Drawings, calcs and a steel schedule your builder can price - Inspections of foundations and steel before they are covered - An opinion of compliance, or BCAR certificates over 40 m² ## What moves the fee - **Ground.** Trees on clay, made ground or a drain under the footprint mean deeper or different foundations and possibly trial holes - **Opening width.** Wide glazed openings need stiff steel designed to the door maker’s deflection limit - **Two storeys.** More load, more steel, and often a party-wall question - **BCAR.** Over 40 m², a Commencement Notice with compliance documentation, an inspection plan and statutory certificates, unless the owner opts out - **Planning drawings.** Some engineers also prepare planning or tender drawings. Others work from an architect’s set ## Bottom line Budget €1,200–€3,500 for extension structural design in Ireland in 2026, plus BCAR certification if the extension is over 40 m². Check that inspections and the final certificate are in the quote. For a fixed fee for your extension, 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 exemption reduce engineering costs?** It removes the planning application, not the structural design. Foundations, steel and roof still need to comply with the Building Regulations, and you'll still want a certificate when you sell. **Is BCAR certification extra?** Usually, yes. Acting as designer and assigned certifier on an extension over 40 m² means preparing the inspection plan, carrying out more inspections and signing statutory certificates. It adds to the basic design fee. Quotes should show it separately. **How do I compare engineer quotes for an extension?** Check that each quote covers the same items: site visit, foundation and steel design, roof structure, drawings, steel schedule, inspections at foundation and steel stage, and the final certificate. The cheapest quote often leaves out the inspections. Sources - [BuildTech: How much does a residential structural engineer cost in Ireland](https://buildtech.ie/blog/residential-structural-engineer-cost-ireland) - [Banrach: How much does a structural engineer cost in Ireland](https://banrach.ie/how-much-does-a-structural-engineer-cost-in-ireland/) - [BeforeYouBuild: House extension cost Ireland 2026](https://www.beforeyoubuild.ie/blog/house-extension-cost-ireland-2026) - [gov.ie: Commencement Notices](https://www.gov.ie/en/service/ebb3b-commencement-notices) 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 - [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.](https://structuralengineer.ie/guide/45m2-extension-exemption/) - [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/) - [How Much Does a Structural Engineer Cost in Dublin? (2026) Typical 2026 fees by job type, the three ways engineers charge, and what a complete quote should include, with sources for every figure.](https://structuralengineer.ie/guide/structural-engineer-cost-dublin/) - [Cost to Remove a Load-Bearing Wall in Dublin (2026) Engineer's fee, steel, propping and making good, with the factors that move the price and sources for every figure.](https://structuralengineer.ie/guide/load-bearing-wall-removal-cost/)