Vertical Foundation Cracks
The good news first: vertical cracks are the most common foundation crack and usually the least serious.
Bottom line: a thin vertical crack (under 1/8") in a poured concrete wall is usually a shrinkage crack from curing. It's not structural, but seal it if water comes through. Have it checked if it's wider than 1/4", growing, wider at one end, or displaced.
Why vertical cracks happen
Poured concrete shrinks as it cures. Long walls often relieve that stress by cracking vertically, frequently near windows, corners or the middle of a long wall. These cracks usually appear within the first year or two and then stop growing.
Vertical vs. diagonal: why the shape matters
- Even width, top to bottom: typical shrinkage
- Wider at the top than the bottom (or the reverse): can point to settlement at one end of the wall, so keep an eye on it and have it checked if it grows
- Angled more than about 30° from vertical: treat it as a diagonal crack, which is more often settlement
Should you repair a vertical crack?
If it's dry and not growing, it's optional. Many homeowners seal it anyway before finishing a basement. If water gets through, seal it from the inside with polyurethane foam injection, which stays flexible and fills the full depth of the crack. A DIY kit is realistic for a single crack. See foundation crack repair for the steps.
When a vertical crack needs a professional
- It's wider than 1/4"
- It keeps growing after the first couple of years
- One side sticks out further than the other
- It runs through the footing, or the floor next to it has dropped