Do I Need a Structural Engineer for My Extension in Ireland?
If you’re planning a house extension in Ireland, you may be wondering whether you need to hire a structural engineer. This article explains the requirements and why structural engineering is essential for most extensions.
The Short Answer: Yes, Almost Always
For virtually all house extensions in Ireland, you will need structural engineering design. This isn’t just good practice – it’s required by Building Regulations and expected by Building Control Authorities.
Building Regulations Requirements
Ireland’s Building Regulations, particularly Technical Guidance Document A (TGD A) – Structure, require that buildings are designed and constructed to safely carry all loads and transmit them to the ground.
For any construction works that require a Commencement Notice (most extensions over 40m²), you must:
- Appoint a competent Design Certifier
- Have structural calculations prepared
- Ensure compliance with structural standards
Even for extensions under 40m² that might qualify for a Commencement Notice exemption, Building Control can request structural information.
What Does a Structural Engineer Do for an Extension?
1. Foundation Design
The engineer assesses ground conditions and designs foundations (strip, pad, or raft) appropriate for your site and loads.
2. Superstructure Design
This includes:
- Wall construction specifications
- Lintels over openings
- Steel beams where walls are removed
- First floor joist specifications
- Roof structure design
3. Integration with Existing Building
One of the most critical aspects is connecting the new extension to your existing house. This includes:
- Removing external walls
- Tying new walls to existing
- Ensuring differential settlement doesn’t cause cracking
4. Drawings and Specifications
The engineer produces structural drawings showing:
- Foundation layouts and details
- Structural sections through the building
- Steel beam and connection details
- Construction specifications
5. Building Control Submissions
Structural calculations and drawings form part of Commencement Notice and compliance documentation.
Types of Extensions That Need Structural Engineering
Rear Extensions
Even a single-storey kitchen extension requires structural design for foundations, steel beams (where opening into existing rooms), and roof structure.
Side Extensions
Side extensions often involve more complex foundations due to proximity to boundaries and existing drains.
Two-Storey Extensions
Higher loads and connection to existing first floors make structural engineering even more critical.
Over-Garage Extensions
Building above an existing garage requires assessment of whether existing foundations and walls can support additional loads.
Wraparound Extensions
Complex geometry and integration with existing building require careful structural coordination.
The Risks of Skipping Structural Engineering
Structural Failure
Inadequate foundations or undersized beams can lead to cracking, movement, or in worst cases, collapse.
Building Control Issues
Without proper structural design, Building Control may:
- Refuse to issue a certificate of compliance
- Require remedial works
- Require retrospective engineering analysis
Insurance Problems
Home insurance may be void or claims denied for works without proper structural certification.
Sale Complications
When selling your home, conveyancing solicitors will check for compliance documentation. Lack of structural certification can delay or prevent sale.
Costly Remediation
Fixing structural problems after construction is far more expensive than proper design upfront.
How Much Does Structural Engineering Cost for an Extension?
Typical structural engineering fees for house extensions in Ireland:
- Single-storey rear extension: €800 - €1,500
- Two-storey extension: €1,200 - €2,500
- Complex extension with steelwork: €1,500 - €3,500
This represents typically 1-3% of construction cost – excellent value considering the risks avoided.
Choosing a Structural Engineer
When selecting a structural engineer, check:
- Chartered status - Look for CEng MIEI (Chartered Engineer, Member of Engineers Ireland) or MIStructE (Member of Institution of Structural Engineers)
- Professional indemnity insurance - Essential protection for you and the engineer
- Experience with residential projects - Ask to see similar projects
- Local knowledge - Understanding of Irish Building Regulations and local authority requirements
Conclusion
For house extensions in Ireland, structural engineering isn’t optional – it’s essential for safety, compliance, and peace of mind. The cost is modest compared to overall construction costs, and the protection it provides is invaluable.
Contact Brickbolt Engineering for professional structural design for your extension project. We provide clear, comprehensive structural solutions that meet all regulatory requirements.
