The short answer
A structural engineer checks the parts of a building that carry load and the signs that those parts may be moving or failing. On a typical inspection they examine the foundations and ground (often via visible evidence and, if needed, trial holes), the external and internal walls for cracking, bulging or leaning, the cracks themselves — their width, pattern and direction, which reveal the cause — the floors for sag or bounce, the roof and chimney, and any beams, lintels and load paths. The key judgement is whether movement is active (ongoing and needing action) or historic (long finished and harmless). They also look for damp, drainage issues and nearby trees, because these often cause structural symptoms. The depth depends on whether it is a focused defect inspection or a whole-property assessment.
A structural engineer is not checking decoration or fittings — they are reading the building for evidence of how it carries load and whether anything is going wrong. The points below cover what they look at and why. Ranges and patterns only; every property differs.
Main things checked
- Foundations & groundmovement, depth, soil
- Wallscracks, bulging, lean
- Crackswidth, pattern, direction
- Floors & roofsag, bounce, spread
- Beams & load pathsadequacy, bearings
The load-bearing elements
The engineer works through the structure systematically, following how load travels from the roof down to the ground — because a defect low in that path, such as a failing foundation, often shows itself higher up as cracking in a wall. Reading the building as a single load path, rather than a list of separate parts, is what lets an engineer tell a symptom from its cause. The elements below are the ones they check on a typical inspection of an existing home.
- Foundations and ground: evidence of settlement or subsidence; trial holes if the foundation needs to be seen.
- Walls: load-bearing walls for cracking, bulging, leaning or signs of overloading; lintels over openings.
- Floors: excessive deflection (sag), bounce, or signs that joists are undersized or rotten.
- Roof and chimney: spreading rafters, sagging ridge, leaning stack or failed support after a breast removal.
- Beams and connections: existing steel or timber beams, their bearings and whether they are adequate for the load.
Reading the cracks
Cracks are the main clue, and the engineer reads them carefully — width, shape, direction and where they appear all point to different causes. Hairline cracks are usually harmless; the engineer is alert to wider, diagonal or stepped cracks that suggest movement.
| Crack sign | Often suggests | Engineer's concern |
|---|---|---|
| Fine hairline cracks | shrinkage / decoration | usually cosmetic |
| Diagonal / stepped cracks | ground movement | possible subsidence |
| Wide, tapering cracks | active movement | needs monitoring |
| Horizontal wall cracks | lateral pressure / wall tie | wall stability |
Indicative patterns for guidance only. Crack interpretation requires a qualified engineer; this table is not a substitute for inspection.
Active versus historic movement
The single most useful thing an engineer establishes is whether movement is active or historic. Active movement is ongoing — the cracks are widening, the building is still moving, and something needs to be done. Historic movement happened long ago, settled, and is now stable — common in older houses and usually no cause for concern. The engineer judges this from the crack pattern, signs of redecoration over old cracks, the building's age and, where it cannot be settled by eye, by fitting tell-tales and monitoring over months. Distinguishing the two is what saves homeowners from paying for remedial work they do not need — a frequent and reassuring outcome.
What they check beyond the structure itself
Structural symptoms often have non-structural causes, so the engineer also looks at the surroundings. They check for nearby trees and vegetation, which can dry out clay soils and cause seasonal movement; drains and gullies, since a leaking drain can wash out the ground under a foundation; and damp and water, which can rot timber and corrode wall ties. They will note recent building work, made-up ground, and anything that has added load — a new heavy roof covering, for instance. By looking at cause as well as effect, the engineer can recommend the right fix: sometimes simply removing a tree and waiting, rather than expensive underpinning.
What they cannot check on a standard visit
It is just as important to understand the limits of a normal inspection, because an honest report will be explicit about them. A standard visit is non-destructive: the engineer assesses what is visible and accessible and does not lift floors, hack off plaster or dig holes. That means several things stay hidden unless further work is commissioned. The foundations cannot be seen without trial holes; the condition of buried drains needs a drainage survey; timber hidden beneath finishes or in inaccessible voids cannot be fully assessed; and whether cracking is active often cannot be confirmed without monitoring over time. Where these matter, the engineer will recommend the next step rather than guess — and that recommendation is a sign of a thorough inspection, not an evasive one. Treating 'further investigation required' as useful information, rather than a non-answer, is the right way to read it: it tells you precisely what is still unknown and how to find out.
- Foundations: need trial holes to inspect directly.
- Drains: need a CCTV drainage survey to confirm leaks.
- Hidden timber: may need opening up to assess decay.
- Active movement: usually needs monitoring over months to confirm.
Frequently asked questions
Does a structural engineer check the whole house?
It depends on what you commission. A focused inspection examines one specific defect — a crack or a wall. A full structural assessment works through the whole property: foundations, walls, floors, roof and load paths. Agree the scope before the visit.
Can a structural engineer tell if cracks are serious just by looking?
Often, yes — crack width, pattern and direction tell an experienced engineer a great deal. But where the question is whether movement is still active, they usually need to fit tell-tales and monitor over months before concluding.
Will the engineer dig up the foundations?
Not usually on a first visit. They assess from visible evidence, and only recommend trial holes — small excavations to inspect the foundation and soil — where the diagnosis genuinely needs the foundation to be seen.
Sources & further reading
Figures on this page are typical UK ranges drawn from published sources and depend on your specific project. They are guidance, not a quotation.