Usually on the older homes and on occasion newer homes undergo differential soil movements.  This causes heave and subsequent cracking of drywall, slabs on grade and footings.

We have never found a single cause for a distressed home. Rather it is a combination of factors that come together. These include expansive soils, loose Sand and Soft Clay deposits within the depth of influence of the foundation.  Other times it is caused by descending slopes very close to the footings and nearby tree roots.