Subsidence is the downward movement of the site on which the building stands. The instability in the underlying soil causes cracks to form in the building structure.
Heave is the opposite. Where subsidence can be caused by shrinking, heave is caused by swelling of the soil underneath. Heave can be caused by the removal of nearby trees which have reduced the soil volume by absorbing moisture via their roots. If the trees is removed, the soil will rewet and can expand significantly in volume.
Heave must be carefully considered in the design of root barriers or when a large tree near to a building is to be removed. This is especially relevant for clay soils which have large potential to shrink and swell. If not accounted for, heave could later disrupt the foundations of a building and cause damage that will look similar to subsidence (cracks in the building etc).
Please contact us if you have any concerns related to tree reduction/removal and heave. We have significant experience in both heave intervention and mitigation measures.