Is My Foundation Crack Serious?
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Most foundation cracks aren’t emergencies. Small hairline cracks may not be a concern at all. Larger or widening cracks suggest movement, and horizontal cracks are particularly concerning because they may relate to soil pressure. Here’s how to read yours.
The four types
1. Hairline vertical crack: watch it
A thin vertical line, dry, not getting longer or wider. Small hairline cracks may not be a concern.
What to do: mark the ends with a pencil and the date, take a photo with a tape measure, and check it each season. If it starts leaking, seal it.
2. Wider vertical or diagonal crack that leaks: seal it
Wider than a hairline, with damp patches or white chalky staining, or water on the floor after rain or snowmelt.
What to do: have it sealed. Most of these are good candidates for interior crack injection.
3. Stair-step crack: get it assessed
A crack that zigzags along mortar joints in a block wall, or steps across a wall.
What to do: send us a photo. It may be settlement or movement, and it’s worth having someone look at it.
4. Horizontal crack or bowing wall: get it assessed soon
A crack running sideways along the wall, especially with the wall leaning or bulging inward. Horizontal cracks may relate to soil pressure, and they are particularly concerning.
What to do: photograph it, mark the ends, and arrange an assessment soon. Don’t patch over it. See horizontal cracks and bowing walls.
Signs a crack is changing
- It’s longer or wider than it was.
- It’s started leaking.
- Doors or windows nearby have started sticking.
- The wall looks like it leans or bulges.
Larger or widening cracks suggest movement.
Check outside too
Walk around the house and look at the exterior foundation. Inspect exterior cracks before snow covers them. Once snow cover is consistent, they’re hard to see until spring.
Not sure?
Send us a photo with a tape measure beside the crack. We’ll tell you which of the four it looks like, and what we’d do.