Tree Related Subsidence
winter a shrinkable soil generally increases in volume, in summer the
reverse occurs. In summer where rainfall is reduced and evaporation
through the increase in temperature is higher; a clay soil will shrink.
In winter as rainfall increases and evaporation decreases; the soil
will swell. Clay soils change their volume in relation to water content;
they shrink as they become drier and expand as they become wetter acting
like a sponge. These seasonal fluctuations can be made worse by adjacent
trees and other vegetation. This can lead to a greater reduction or
increase in the volume of a clay soil leading to enhanced ground movement
and resulting in structural damage to a buildings foundations.