Quality · 8 min read
Why concrete cracks, and which cracks need an engineer
Shrinkage, settlement and structural movement can look similar at first glance. Here is how we record and escalate them.
Reviewed August 2026
Cracking is a symptom, not a diagnosis
Concrete changes volume as it cures and as temperature and moisture move. Fine surface cracks can be cosmetic; a widening diagonal crack, repeated movement or exposed reinforcement needs professional assessment. The pattern, width, location and change over time matter more than a photograph taken once.
Record before repairing
- Mark the ends and date the observation
- Measure width with a crack gauge where possible
- Photograph the same view at regular intervals
- Note nearby leaks, excavation or unusual loading
- Do not conceal an active crack with putty before assessment
Escalate these signs promptly
- Cracks that widen over days or weeks
- Diagonal cracks from door or window corners
- Cracks accompanied by a sloping floor or jammed opening
- Rust staining, spalling or visible reinforcement
- Repeated water ingress through a structural member
The repair follows the cause
Sealing a crack is not the same as solving movement. Repairs may range from a compatible surface treatment to resin injection, waterproofing work, load correction or structural strengthening. A qualified structural engineer should specify repairs where movement or capacity is in question.