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Is this foundation crack serious?
Direction, width, and movement tell you most of what a crack means. Answer the questions and get a risk level with next steps.
What common crack patterns mean
| Pattern | Likely cause | Concern |
|---|---|---|
| Hairline vertical crack, poured wall | Shrinkage while concrete cured | Low |
| Vertical crack that leaks | Shrinkage crack letting water in | Low (water issue) |
| Diagonal crack from a window corner | Uneven settlement | Moderate |
| Stair-step crack in block or brick | Settlement under part of the wall | Moderate to high |
| Horizontal crack in a basement wall | Soil pressure pushing the wall in | High |
| Any crack wider than 1/4 in | Real movement, not shrinkage | High |
| Horizontal crack with bowing | Wall is failing under soil pressure | Urgent |
How to read a crack
Direction
Vertical cracks in poured concrete usually come from shrinkage. Diagonal and stair-step cracks usually mean one part of the foundation is settling more than another. Horizontal cracks in basement walls usually mean soil pressure from outside, the pattern that most often leads to bowing walls.
Width
Hairline cracks are rarely structural. Anything wider than 1/8 inch deserves monitoring, and wider than 1/4 inch deserves a professional opinion.
Movement
An offset, where one side of the crack sticks out past the other, and a crack that is still growing both show active movement. Movement matters more than how the crack looks today.
Once you know what is needed, price it with the crack repair, bowing wall, or sinking foundation calculators or check a quote with the quote checker.
Frequently asked questions
What foundation cracks are normal?
Thin vertical or slightly diagonal cracks in poured concrete walls, under 1/8 inch wide, with no offset, are usually shrinkage cracks. Almost every poured foundation has a few. Seal them if they leak and keep an eye on them.
When should I worry about a foundation crack?
Worry about horizontal cracks in basement walls, stair-step cracks in block walls, cracks wider than 1/4 inch, cracks where one side is offset, cracks that keep growing, and cracks together with sticking doors or sloping floors.
How do I measure if a crack is getting bigger?
Mark both ends with a pencil line and the date, and photograph it with a ruler across the widest point. Check monthly. For more precision, a crack monitor gauge costs about $15–$30.
Who should I call about a foundation crack?
For a clear diagnosis, a licensed structural engineer, who charges $500–$1,500 and does not sell repairs. Foundation contractors offer free inspections, but they also sell the fix.
Can I fix a foundation crack myself?
You can seal non-structural shrinkage cracks with a DIY polyurethane or epoxy injection kit for $30–$100. Do not DIY horizontal cracks, bowing walls, or cracks with offset. Those need a structural fix.