### Instruction: What problems can expansive soil cause?
### Response: Expansive soil can cause foundation problems for homes built on such sites.  The soil expands or swells with moisture and shrinks in dry weather.  This causes movement in the foundation year in and year out.  This can result in foundation cracks and sinking of floors.  This can also cause, as a secondary effect, cracks in the walls and sticking or jamming of doors.