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Water is the main enemy in
expansive soils problems. There is either too much water,
causing the soil to swell, or not enough, causing the soil
to shrink.
If
all soils beneath a foundation swell uniformly or shrink
uniformly, it is unlikely to cause a problem. But when only
part of the foundation heaves or settles, differential
movement causes cracks and other damage.
Most
differential movement is caused by differences in soils
moisture. After construction, soil beneath part of the
foundation becomes wetter or drier than the rest of the
soil.
Here is why this happens:
 Evaporation
Hot dry wind and intense heat will often cause the
soil to shrink beneath the foundation. This settlement may
cause cracks to appear throughout the structure.
Transpiration
Tree roots may
desiccate the soil beneath a home causing the soil to shrink
and the home to settle.
Plumbing Leaks
Water from plumbing
leaks is often a cause of foundation problems.
Drainage
Improper
drainage is a leading cause of foundation failure. Excess
moisture will erode or consolidate soils and cause settlement.
Inferior
Foundation Construction
Insufficient steel and
inferior concrete will contribute to movement in the slab.
 Inferior
Ground Preparation
Soft, low density soils
and/or improperly compacted soil beneath a home is the leading
cause of foundation failure. Cut and fill situations should be
properly prepared before the soil is ready to support a
structure.
Poor Soil
Conditions
Poor soil and its expansion and/or
contraction contribute to foundation failure.
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