Short answer: Thin vertical cracks in poured concrete walls are common and usually only a leak concern. Horizontal cracks, stair-step cracks in block walls, cracks that keep widening, and walls that lean inward can mean the wall is under pressure and should be inspected.
Cracks that are usually minor
Poured concrete shrinks as it cures, so thin vertical or slightly diagonal cracks are very common, especially near windows and corners. If a crack is hairline thin, isn't widening, and the wall is straight, it's typically a water concern only.
Leaking cracks in poured walls are commonly sealed by injecting them from the inside with epoxy or polyurethane. Fixr puts crack injection at $250 to $1,000 per crack.
Cracks that need an inspection
- Horizontal cracks, especially partway up a wall. These often come from soil pressure pushing the wall inward.
- Stair-step cracks that follow the mortar joints in a block wall.
- Cracks wider at one end than the other, or that have grown since you first noticed them.
- Walls that bow or lean when you sight down them or hold a level against them.
- Cracks with one side offset from the other.
Why walls bow
Clay soils that swell when wet, and freeze-thaw cycles in winter, push against basement walls. Over years, block walls can bow inward and poured walls can crack horizontally. Water pressure from saturated soil adds to the load.
Common repairs and costs
| Repair | Typical cost | Source |
|---|---|---|
| Crack injection | $250 to $1,000 per crack | Fixr, 2026 |
| Bowing wall repair | $2,000 to $7,500 per wall | Today's Homeowner, 2025 |
| Wall anchors | $80 to $150 per foot, usually every 5 feet | Today's Homeowner, 2025 |
| Bowing wall repair (all methods) | $4,000 to $12,000 | Angi |
Steel beams braced between the floor and joists, anchors set into the yard, and carbon fiber straps are the three most common methods. The right one depends on how far the wall has moved and what's outside it.
Frequently asked questions
How do I track whether a crack is growing?
Mark both ends of the crack with a pencil and the date, and measure its width. Check it every few months. Growth means it's time for an inspection.
Should I fix the crack or the water problem first?
Structural problems come first, since drainage installed against a moving wall may need to be redone. A good contractor will look at both in one visit.