Can Moisture Crack Your Foundation?

Changing Moisture Levels

• Rain, snow and dry weather all influence ground moisture levels, which are constantly changing. Soil acts like a sponge, absorbing and expelling moisture with changes in the weather. Some soils, such as clay, are particularly prone to absorbing water. When soils take on moisture, they tend to expand. As soils release moisture in drier conditions, they tend to contract.

Foundation Movement

• Soil movement through expansion and contraction brought on by moisture -- or a lack thereof -- transfers to a home’s foundation. The foundation rises as soil picks up moisture, and it settles back down as soil releases moisture. As long as the foundation moves about the same in each direction, no problems arise. Small cracks may form, but they typically disappear with changes in moisture levels. Sloping the yard away from the home, and using gutters and downspouts direct water away from the foundation. This helps minimize the effect of soil absorption. Extremes between absorption and contraction as a result of water load can cause more damaging cracks in the foundation.

Differential Shifts

• Foundations seldom move up and down exactly the same amount. They don’t even move at the same rate at different places around the home. Trees, flower beds, sunlight, even changes in soil composition result in differential shifts -- the foundation moving at different rates based on how much moisture soils absorb and release around the foundation. Differential shifts can cause the foundation to settle awkwardly, resulting in foundation cracks, uneven floors, doors and windows that fail to close properly, or drywall cracks.

Drought Conditions

• Extreme drought conditions, such as those suffered by much of the United States in 2012, cause foundation cracks in a different way. In droughts, soils lose almost all of their water. This causes severe soil shrinkage, which leaves air pockets or voids behind. This lack of sufficient moisture also causes cracked foundations. Some experts recommend hydrating soils a few feet away from the home (not the foundation itself) in order to counter extreme dry soil conditions.

Freezing

• Should water seep into cracks, then freeze, it has the potential of widening those existing cracks. Even when foundations are well below the frost line, water closer to the surface can freeze inside the upper ends of cracks. In addition, water trapped in the soil can freeze. Should that happen, the soil can move as much as 10 percent, enough to cause stress on foundations, which could lead to cracking.