Symptoms
- Thin crack, often vertical, under about 1/8 inch wide
- Crack has looked the same for a long time
- No accompanying water intrusion, bowing, or offset edges
Likely causes
- CommonNormal concrete shrinkage as it curesPoured concrete foundations commonly develop small vertical cracks within the first few years.
- CommonMinor, stable settlingSmall amounts of uneven settling are normal and often stop after the first few years.
- PossibleEarly sign of more significant settling or water pressureA crack that widens, becomes diagonal, or is accompanied by other symptoms deserves closer attention.
What to do
- Measure the crack's width with a coin or crack gauge and note the date.
- Check whether the two sides of the crack are level with each other (offset suggests movement, not just shrinkage).
- Look for water staining, efflorescence, or dampness at or near the crack.
- For a stable, dry hairline crack, seal it with an appropriate concrete or masonry crack filler to keep out moisture and radon.
- Recheck the crack every few months, remeasuring width to catch any change early.
- Note any related symptoms elsewhere, like sticking doors or new drywall cracks upstairs.
- Have a foundation specialist evaluate if the crack grows, becomes diagonal or horizontal, or leaks.
Tools and parts
- Crack gauge or coin
- Flashlight
Concrete crack sealantSearch: “concrete foundation crack sealer”
When to call a pro
Call a foundation repair specialist or structural engineer if the crack is widening, diagonal, horizontal, or leaking.
Safety
Generally low risk
Generally low risk for a careful person. Stop if anything looks different from what this guide describes.