GLOSSARY · ADELAIDE
Slab heave
Plain English
Upward movement of a concrete slab caused by expanding reactive clay underneath. Often visible as raised floors, cracked tiles, jammed doors.
Slab heave occurs when reactive clay soil underneath a concrete slab absorbs water and expands. The slab moves with it. Heave can be uniform (whole slab rises evenly - less damaging) or differential (parts of the slab rise while others don't - very damaging).
Common causes of localised heave: leaking under-slab plumbing, downpipes discharging next to footings, garden beds with heavy watering against the building.
Inspectors will look for raised floor surfaces, cracked floor tiles, doors that won't close, gaps opening at skirting boards, and any patterns suggesting the slab has moved unevenly.