Dual Pier System
  Warning Signs
  Basic Causes

Trees---The root system generally extends out as far as the drip line (outer edge of branches). If the branches overhang the roof, then the roots probably extend under the foundation. They will draw water out, and the soil will shrink unless moisture can be maintained.
Shrubs---When placed close against the house, their roots draw water from under the foundation and allow the soil to shrink; but overwatering can cause swelling.
Uneven Drainage---If water does not drain away from the house or puddles stand close to the house after a rain, the soil will swell in the areas that stay wet. Areas that do not get enough moisture will shrink.
Pipes/Drains---Cracks or breaks in the lines could add enough moisture to cause swelling or erosion in the surrounding soil.
Pools/Ponds/Tubs---Cracks or leaks as well as excessive splashing or spraying can affect the surrounding areas causing swelling of the soil.
Fences/Walls---These can interfere with the normal flow of water runoff and cause excessive moisture to accumulate in one area while keeping another area too dry.
Driveways/Sidewalks/Patios---These thin slabs of concrete or other materials exclude moisture from the underlying soil. If close to the building, they rob the foundation of needed moisture and allow shrinking. However, other areas may be kept wet due to runoff from these surfaces.
Gutters---Rain or snow on the roof is collected and transported to downspouts which direct the water into drains or outflow on the surface. The outflow should be directed at least three feet from the house to avoid foundation problems, and the runoff should be directed away from the house.
Causes Due to Mother Nature
Faults---There are a number of known fault zones in different areas of the country. Along these zones one side shifts with reference to the other. This can tear up streets, sidewalks, driveways, pools, homes, and buildings. Faults have been mapped, and builders are careful to avoid them. Excessive withdrawal of well water and heavy construction are responsible for movement along these zones.
Drought---Extended periods without adequate rainfall and unusually hot summers upset the natural balance of moisture in the soil. The homeowner can restore the balance by properly watering during these periods. However, too much watering also upsets the balance. Local governments sometimes restrict the watering of lawns to conserve drinking water supplies.
Floods---Heavy rains that cannot be carried off by natural and man-made drainage create the same problems caused by overwatering.