What is a subsidence crack?
A subsidence crack is a crack in a structure caused by part of the building sinking. Because the movement is uneven, with one part going down more than another, a subsidence crack is rarely just a cosmetic issue. As long as the cause remains, the crack usually grows over time. In Dutch it is called a zakscheur.
How it differs from other cracks
- Shrinkage crack: caused by materials drying out and shrinking. Usually fine and not structural.
- Settlement crack: caused by one-off settlement after the building is fully loaded. The structure usually stabilises afterwards.
- Subsidence crack: caused by ongoing, uneven sinking. The most serious type.
Warning signs
- Cracks that get wider or longer over time.
- Windows and doors that start to stick.
- Leaning walls or sloping floors, visible with a spirit level or plumb line.
- Stepped cracks running through the mortar joints of brickwork, often near corners or above openings.
Application in practice: what to do
- Record the crack: photograph it with a ruler alongside and note the date.
- Monitor it with a crack gauge: measure the width at regular intervals to see whether it is stable or still moving.
- Call in a structural engineer: only an expert can tell whether it is a subsidence crack and how serious it is.
- Have the foundations investigated: with ongoing movement the cause must be found, for example decaying timber piles or a fluctuating water table.
- Fix the cause before the crack: filling or replastering only makes sense once the movement has been stopped by foundation repair. Otherwise the crack will reopen.
Related terms
- Differential settlement
- Settlement crack
- Shrinkage crack
- Crack
- Foundation survey
- Foundation repair
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