Causes

Causes of Foundation Problems

Foundations are built directly on the earth. The foundation load is dependent upon the strength of the soil beneath. In nature, soil is rarely homogeneous. It tends to develop in layers or stratum, each with individual strengths and weaknesses. Figure 1.1 illustrates this stratification.

Water is the primary cause in soil problems. Whether there is too much water, causing the soil to swell, or not enough, causing the soil to shrink. If all the soil layers beneath a foundation swell or shrink uniformly, a problem is unlikely to occur. Where only part of the foundation heaves or settles, the uneven movement causes cracks and other damage.

Expansive soils, the gain in moisture, is a more serious threat to the foundation. Plumbing leaks, subsurface water like wet weather or a high water table, or surface water are the primary source of moisture gain. Improper drainage of landscape water or rainwater is considered surface water. Ensuring proper surface drainage away from the foundation will assist in keeping the foundation solid and intact.

Soil may lose moisture, due to drought, causing the foundation to settle. Settlement is greatest near the perimeter of the foundation, where the soil dries quicker.

During construction, if the load bearing soil is not compacted enough, the foundation is subject to settlement as the supporting soils compacts under load.

When a foundation spans over differing soil conditions, the foundation may settle differently. When one half of the foundation is supported by expansive clay and the other half on rock, the amount of movement varies from one half to the other. This poorly designed foundation system will damage the foundation and structure due to the differential movement.