A settlement crack is a crack in a foundation, wall, or slab caused by the ground underneath moving or compressing unevenly, so one part of the structure drops relative to another and the material cracks to relieve the stress.
Settlement happens because soil isn't uniform: fill dirt compacts more than undisturbed soil, wet clay expands and contracts, and a footing that's too shallow or too narrow transfers more load per square inch than the soil underneath can support without moving. Settlement cracks tend to be widest at one end and taper to a hairline at the other, and they often run diagonally rather than straight up and down, following the direction the structure is dropping.
Up here, settlement is often tied to how the footing was built in the first place: one poured on fill soil instead of undisturbed ground, or one that sits above the local frost line, moves as the ground freezes and thaws each winter. Not every settlement crack means a rebuild. Some can be repaired by underpinning or repointing once the movement has been evaluated and confirmed to have stopped, while an active crack that keeps opening needs the footing addressed first.
More masonry vocabulary from the glossary.
The services where this term comes up.
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