When do you need a structural engineer? Book one when: cracks are diagonal, wider than ~5mm, growing or recurring; doors/windows stick and floors slope without explanation; walls bulge or lean; a survey, lender or insurer asks for one; any alteration touches structure (walls out, lofts, extensions); or you're buying with any flagged movement. Contact same-day when: sudden significant cracking, movement after impact or nearby excavation, or visible distress you can watch progressing. Monitor first when: hairline, static, pattern-benign cracking with no companions.
Call the same day
- Sudden wide cracking, especially with sounds of movement or debris
- Cracking or distortion appearing during nearby excavation, demolition or your neighbour's basement dig
- Impact damage — vehicle, fallen tree — to structural elements
- Bulging or leaning that is visibly worse than last week
- Anything making you question whether part of the building is safe to use — and until answered, keep people away from the affected area
Book promptly (days–weeks)
- Diagonal, stepped, >5mm, recurring or seasonal cracking
- Sticking doors/windows plus sloping or springy floors — the movement chorus
- Survey, valuation, lender or insurer requesting an engineer's opinion
- Purchase with flagged movement or undocumented alterations — before exchange, always
- Planned structural work: wall removals, lofts, extensions — at design stage, before tender
- Post-works verification or regularisation of past alterations
Monitor first (and how)
Hairline cracks, static, in expected places (plaster joints, material junctions, new-build drying), with no companion symptoms: photograph against a ruler, pencil-date the ends, recheck monthly and across a season. Change promotes it to 'book promptly' — and your dated record makes that assessment faster and cheaper. No change across a seasonal cycle usually confirms the benign reading. The one caveat: monitoring is for genuinely ambiguous minor cracking, not a procrastination scheme for cracking that already meets the booking criteria above.
Engineer, surveyor, or builder?
Route by question. Structural engineer (IStructE or ICE chartered): why is it moving, is it safe, what beam/foundation/remedy — analysis and design. Building surveyor: overall property condition (RICS Levels), breadth over structural depth — and they refer to engineers when movement appears. Builder: executes specified work — invaluable, but diagnosis and design aren't the trade, and 'my builder says it's fine/says it needs underpinning' are the two sentences that most reliably precede an engineer being called anyway. Cheapest sequence: right professional, first time.
This guide provides general information only and is not formal structural advice for any specific property. The cause of movement or damage should always be established by proper professional assessment before repairs are commissioned.