Key points
- Record where the crack starts and ends, not just its maximum width.
- Look for related distortion at doors, windows, floors and junctions.
- Change over time is often more important than a single photograph.
- A crack monitor can record movement but does not by itself identify the cause.
What makes a crack more significant?
No single crack width automatically proves subsidence. Surveyors consider geometry, continuity, location, age of the building, previous alterations and whether other parts of the building show related movement.
Diagonal cracking around openings, stepped cracking through masonry, separation at extensions and movement accompanied by distortion can justify a more focused assessment, particularly if the pattern appears recent or progressive.
- widening or repeated reopening after repair;
- several related cracks forming a consistent movement pattern;
- doors or windows becoming newly difficult to operate;
- noticeable sloping, rotation or separation at structural junctions;
- recent movement following alterations, drought, drainage problems or nearby works.
What should you record before an inspection?
Useful evidence includes dated photographs from the same viewpoint, approximate crack widths, notes of when the crack was first noticed and any recent changes to the property or surroundings.
- building works or wall removals;
- drainage leaks or repairs;
- tree removal, pruning or new planting;
- long dry periods or unusually wet conditions;
- previous underpinning or structural repairs.
Do not fill and redecorate a changing crack immediately if the purpose is to understand whether movement is continuing. The visible evidence may be useful.
When is a focused movement investigation proportionate?
If cracking is localised and the main question is whether there is evidence of structural movement, a focused defect investigation can be more proportionate than commissioning another whole-property Home Survey.
Depending on the findings, the next step may be monitoring, drainage investigation, opening-up, documentary checks, or referral to a structural engineer. Not every crack requires structural engineering and very few movement cases require underpinning.
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Crack & Structural Movement Investigation
A focused inspection considers the crack pattern, related distortion, alterations, drainage, vegetation and other visible context before recommending proportionate next steps.
Common questions
Questions people often ask
Does a 3 mm crack mean subsidence?
Not by itself. Width is one factor. Pattern, location, direction, related distortion, change over time and building context all matter.
Should I ask a structural engineer first?
Sometimes, but not automatically. A building surveyor can often establish whether the visible pattern justifies structural engineering, monitoring or another specialist investigation.
Can old cracks still matter?
Yes. Historic cracking can reveal previous movement, alterations or weak junctions even where there is no evidence that movement is currently active.
Sources and review
Recognised sources used for this guidance
These sources support the general guidance above. They do not replace property-specific inspection, current legal advice or specialist testing where those are needed.