Design team
Structural engineers: when you need one and what they provide
If you are removing a wall, forming an opening, adding a floor or building an extension, someone has to prove the building will still stand up. That proof is a structural engineer's design and calculations, and building control will ask for it.
What you are buying
- Calculations for beams, lintels, padstones, foundations and floors.
- Structural drawings and details the builder works from.
- Foundation advice, including trees, drains and ground conditions.
- Sometimes site inspection at critical stages, such as foundations before pouring.
When it is normally needed
- Removing or altering a load-bearing wall.
- Any extension with new foundations.
- Loft conversions, where new floor structure and roof support are required.
- Basements, underpinning and anything affecting a neighbouring structure.
- Where building control asks for it, which is the practical trigger in most projects.
How it affects money and programme
Structural design is usually a small fee that determines a large cost. Steel sizes, foundation depth and floor build-ups move the builder's price far more than finishes do.
Getting calculations late is a common cause of delay and variation. If a builder prices without engineering information, expect the number to change once it arrives.
Case-style example
A steel that grew
A homeowner budgets for a single beam to open up a kitchen. The engineer's calculations, produced after the builder quoted, call for a heavier beam, two padstones and a new foundation pad in the corner.
None of that is unreasonable, but none of it was in the quote. The variation arrives at the worst possible moment: mid-strip-out, when stopping is expensive.
The lesson is sequencing. Structural information before pricing turns a variation into a line in the original quote.
How The Construction Clinic helps with this decision
We do not carry out structural design or check calculations. We help you see whether your project has the technical information it needs before you price it, and what a quote is likely to be assuming without it.
Common questions
Questions homeowners ask about this
Who appoints the engineer, me or the builder?
Either arrangement is normal. If the builder appoints them, be clear that the design is still being produced for your building and ask for a copy of the calculations and drawings.
Does building control accept the engineer's calculations automatically?
They review them. Straightforward domestic calculations are usually accepted, but comments and revisions are common and take time.
Can I reuse calculations from a similar house?
No. Loads, spans and ground conditions are specific to your building.
Do you provide engineers?
No. We are homeowner guidance, not a directory or a design practice.