Heave is upward movement of the ground beneath a building, most commonly caused by clay soils swelling as they regain moisture — often after a large tree is removed — or by frost action and certain chemical reactions in fill. It produces cracking patterns that differ from settlement, and it needs an engineer's diagnosis.
Where mature trees have been drawing moisture from clay soil for years, removing them allows the clay to rehydrate and expand. That expansion can lift foundations, floors and walls, sometimes over several years. Heave can also arise from frost in susceptible soils and from expansion within certain fill materials.
Designing for heave is different from designing for settlement. Solutions include deeper foundations with compressible void formers beside and beneath them, suspended floors rather than ground-bearing slabs, and careful management of tree removal timing on sensitive sites.