Structural Engineering for House Extensions: Foundations, Walls & More

Why Involve a Structural Engineer Early?

Involving a structural engineer at the start of your house extension project provides significant benefits:

• Faster Building Control approval — detailed structural calculations speed up the submission process
• Lower costs and reduced risk — identifying structural challenges during the design phase avoids expensive revisions later
• Better coordination with your architect — structural engineers ensure the architect's design can be safely built

What Does a Structural Engineer Do for Extensions?

A structural engineer ensures your extension is safe, durable, and compliant with UK regulations:

• Designing foundations — recommending the best foundation type (trench fill, raft, etc.) based on soil type and load requirements
• Assessing load-bearing walls — calculating and designing support systems like steel beams if walls are being removed
• Providing structural calculations and drawings — the technical documentation required for Building Control approval and for guiding your builder

Wall Removal for Extensions

It's very common for homeowners to remove an existing wall as part of an extension project — creating a larger open-plan space flowing from the original house into the new extension.

This is a significant structural change. A structural engineer will assess whether the wall is load-bearing and, if so, design a suitable steel beam to ensure the upper floors and roof remain properly supported.

Cost Guidance

The cost of a structural engineer for a house extension varies by project size and complexity:

• Small projects (simple beam calculations, single-storey) — typically £250 to £750
• Larger or multi-storey extensions — typically £1,000 to £2,000

Our wall removal calculation packs start from £450 and include the full technical pack your builder and Building Control need.

Need professional help with this?

Wall Removal Calculations — fixed price from £450, including site visit and Building Control-ready documentation.