Why Concrete Cracks

Concrete shrinks slightly as it cures. Small hairline cracks from this process are normal. Control joints are placed to guide where those cracks form, so they end up in planned locations rather than random spots.

If the ground under a slab moves — from poor base preparation, soft soil, or erosion — the concrete follows. Settlement cracks often show up along with vertical displacement.

A slab poured for foot traffic won't behave the same way under a work truck. Loads beyond what the slab was designed for can cause cracks.

Water sitting on or under a slab creates ongoing stress. Correcting drainage often extends how long a repair or new pour lasts.

Concrete expands and contracts with temperature changes. Expansion joints give it somewhere to move. Without them, the slab may crack to relieve stress on its own.

Cracks that keep widening, cracks with displacement, or cracks accompanied by drainage changes are worth an evaluation. Hairline cracks in the middle of an otherwise sound slab usually are not.