Many cracks are not serious
Buildings move constantly with temperature, moisture and seasonal changes, and many resulting cracks are minor or cosmetic — fine hairline cracks in plaster, shrinkage cracks in new plaster or render, and cracking at junctions of different materials are common and usually not a structural concern.
What a surveyor looks at
Significance is judged from several factors together rather than width alone: how wide the crack is, its direction (vertical, horizontal or diagonal), where it is (around openings and at corners is more relevant), whether it appears both internally and externally in the same location, and — importantly — whether it is stable or actively progressing.
Cracks that are wide, diagonal and tapering, that follow the mortar in a stepped pattern through brickwork, that coincide with sticking doors or windows, or that appear to be worsening are indicators that closer investigation may be required.
If you are concerned
As progression is often a key question, a single inspection cannot always give a definitive answer — monitoring over time or a structural engineer may be needed. A survey records and explains the cracking, gives an informed view of likely cause and significance, and tells you what, if any, further investigation is sensible before you commit.
Key takeaways
- Many wall cracks are minor and cosmetic, although this depends on their width, pattern, location and whether they are changing over time.
- Width, direction, location and progression are judged together.
- Diagonal, tapering, stepped cracks around openings may warrant a closer look.
- Whether a crack is actively progressing is often a key question.
- Suspected significant or progressive cracking may need monitoring or structural engineer input.
Frequently asked questions
How wide does a crack have to be to be a problem?
Width alone is not decisive — a fine crack that is progressing can matter more than a wider stable one. Surveyors weigh width together with direction, location and whether the crack is active.
Should I worry about cracks in a house I'm buying?
Most cracking is not a barrier to purchase, but it should be properly assessed. A survey explains what the cracking indicates and whether further investigation is advisable.
Can you tell from one visit if a crack is serious?
Often the evidence allows an informed view, but because progression matters, some cases need monitoring over time or a structural engineer to be definitive.
This guide is general information, not advice on a specific property. Every building differs — for findings specific to a property you are buying, book a survey.