Expansive soils, rich in clay minerals like smectite, swell when absorbing water and shrink when drying out. This volume change can damage buildings and structures by exerting pressure or reducing support.

During droughts, these soils contract, potentially harming structures. When moisture returns, the soil expands again, creating a cycle of stress. This issue is common in regions with alternating dry and wet periods, such as Houston, where soil expansions of 10% or more are typical.