Short answer
Usually not immediately, but cracking should be understood rather than ignored. Fine hairline cracking in plaster is normally cosmetic. Cracks that are wide, diagonal, stepped, growing, or accompanied by sticking doors, sloping floors or bulging walls deserve prompt assessment. Anything suggesting instability — a leaning wall, a sagging beam, spalling concrete exposing corroded reinforcement, or sudden movement — should be treated as urgent and the area kept clear until an engineer has advised. Photographing and dating cracks is the single most useful thing an owner can do.
Branded guidance note, prepared for project records and circulation to your team.
A practical way to gauge significance
- Hairline, in plaster only, stable over time: usually cosmetic
- Up to around 5 mm, stable, single location: assessment advisable but rarely urgent
- Wider than 5 mm, tapering, stepped, or widening: engineer assessment recommended
- Any sign of instability, sagging or sudden movement: treat as urgent
What to record before an inspection
- Photographs with a ruler or coin for scale
- The date each crack was first noticed
- Whether it changes with the seasons
- Any works, leaks, tree removal or excavation nearby
How BES is typically involved
- BES gives a clear conclusion — cosmetic, monitor, or remedial action required — rather than an open-ended caveat.
- Where risk is present, immediate precautions are advised on site.
- Monitoring can be specified and reviewed by BES over an agreed period.
Typical process
- 01Photograph and date the cracking
- 02Inspection
- 03Assessment of pattern and cause
- 04Monitoring where required
- 05Report and recommendations
Common misconceptions
Commonly assumed
“A wide crack always means serious damage.”
In practice
Width alone is a poor indicator; pattern, location and whether it is progressive matter more.
Commonly assumed
“If the crack has been there for years it is safe.”
In practice
Long-standing cracks are often stable, but stability should be confirmed, not assumed.
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