Vertical Foundation Cracks: When They're Normal and When They're Not
Updated · By the Roof to Footing editors
Vertical foundation cracks, the ones running straight up and down a poured concrete wall, are the most common kind and usually the least serious. Concrete shrinks as it cures, and a long wall relieves that stress by cracking, often near windows and at intervals along the wall. A thin vertical crack that isn't growing or leaking is typically cosmetic. It becomes a concern when it's wide, uneven, offset, or keeps getting bigger.
Normal vs. worrying
| Probably normal | Get it checked |
|---|---|
| Hairline to about 1/8 inch wide | 1/4 inch wide or wider |
| Same width top to bottom | Much wider at the top or the bottom (a "V" shape) |
| Both sides of the crack flush | One side sticks out past the other (offset) |
| Not growing over months | Getting longer or wider |
| Dry, or damp only in heavy rain | Steady water, or soil coming through |
| Poured concrete wall | Stair-step cracks in a block wall, or any horizontal crack |
A crack wider at the top often means the corner of the house is settling; wider at the bottom can mean the middle of the wall is heaving or settling. Either way, that's a job for a structural engineer, and the fix may involve push piers or other underpinning. Horizontal cracks are a different problem entirely; see horizontal foundation crack repair.
How to monitor a crack
- Mark both ends of the crack with a pencil line and the date.
- Measure the width at its widest point with a crack gauge or a set of feeler gauges and write it down.
- Take a photo with a ruler in the frame.
- Check again every month or two for a year, including after the wettest and driest seasons.
A crack that doesn't change over a full year of seasons is very likely a stable shrinkage crack.
Repair options
The two common repairs are injections from the inside:
- Epoxy injection bonds the two sides of the crack back together and restores strength. Use it when the crack is dry and stable and you want a structural repair.
- Polyurethane injection expands to fill the crack and stays flexible. Use it when the main issue is water leaking through; it handles small future movement better but doesn't add strength.
Professionally injected vertical cracks typically cost about $250 to $800 per crack, according to HomeGuide. DIY kits exist and work on narrow, accessible cracks in poured walls if you follow the directions closely.
From the outside, excavating and applying a waterproof membrane over the crack is more expensive but stops water at the source. It's common when several cracks leak or the exterior waterproofing has failed.
Keep water away
Even a harmless shrinkage crack will leak if the soil against it stays saturated. Point downspouts away from the house, keep the soil graded away from the foundation, and clean gutters. Most "leaking crack" calls end with a drainage fix.
Block walls are different
Concrete block walls don't get shrinkage cracks the same way. Vertical cracks in block usually follow the mortar joints in a stair-step pattern and point to settlement or soil pressure. Have them looked at rather than injecting them.