Hairline crack A hairline crack is a very narrow surface crack that typically forms as concrete cures or experiences minor movement. It is one of the smallest visible crack types.
Hairline cracks often result from normal drying shrinkage rather than structural failure. While they may initially be cosmetic, they can allow moisture to enter the concrete if they widen over time. Periodic inspection helps determine whether additional repairs become necessary.
Frequently Asked Questions About Hairline crack
What is a hairline crack?
A very narrow surface crack that forms as concrete cures or experiences minor movement.
Is a hairline crack a DOT violation?
Generally no. It does not usually meet the substantial-defect criteria, which require specific widths, depths or displacement.
Should hairline cracks be repaired?
Not urgently, but they should be monitored. A crack that widens can let water into the slab and base and progress into a real defect.
What causes them?
Normal drying shrinkage as the concrete loses moisture, plus minor thermal and load movement.