Foundation problems in large areas of Texas are the result of building on soils more suited to agriculture than homes. The houses are built on soil that expands and contracts violently. Foundation issues are more costly than tornadoes in Texas, according to Dr. Allen Poor, of the Construction Research Center at the University of Texas at Arlington.
Most houses in this area are built directly on the ground, more commonly referred to as slab-on-grade. As the result, the soil moves and so does the house. Engineers have tried various methods of reducing soil movements. These include water injection, lime stabilization and chemical injection. Although these reduce soil movement, we still see foundation problems occurring. Many builders don’t attempt to stabilize the soil and these houses are built on un-stabilized soil. When a house is built on a fill, it is important to properly compact the soil. If this is not done under controlled moisture conditions, an expansive soil will move with the weather (rain or dry).
Conventional concrete slab foundations use reinforcing steel placed on a grid within the slab, whereas post tension cable construction places the concrete under compression and creates a more rigid structure. Even with this increase in rigidity, the slab can still bend and rotate (settle or heave).