The first category of foundation concerns is latent defects, which generally occur within the first 12 to 24 months. Latent defects may be attributed to several issues: improper design, improper soil preparation, improper material handling or improper application. Proper soil preparation, before construction occurs, requires removing the top four to six inches of soil and the organic vegetation. If the organic material is not removed, it will deteriorate and cause a void under the slab; which will result in a loss of support for the foundation. Soils, without proper preparation, will compress under the weight of a building causing foundation movement. A foundation must not only be designed to handle the anticipated load of the structure, but also the intended contents of the structure. An improperly designed foundation will move under the applied load causing damage to the structure. Proper workmanship is necessary. If the concrete is not mixed properly, not placed properly or is not given enough time to set, it may not reach its design strength. As a result, the improper workmanship may result in movement as the load of the building is applied.

The second category of fondations concerns is long-term problems, which occur after the second year. There are generally only two major causes of significant foundation movement. The first, which is least likely, is a change in the usage of a building. If a building is converted to a use for which it was not designed, and the new usage has a higher load requirement, movement or cracking in the foundation can occur. The second and most likely cause of foundation problems is moisture. Foundation moves when the soil either shrinks (dry) or expands (wet). The greater the expansion and contraction of the soil, the greater the potential for foundation damage. Proper attention to the amount of moisture in the soil can prevent many foundation concerns. A preventative step during periods of drought, is to inspect the soil around a foundation. Over dry soil will shrink and pull away from the foundation. This will normally occur first on the south and west sides of the building. The placement of a soaker hose, set to a slow trickle, 18 to 24 inches away from the foundation will solve this problem. The presence of large bushes or trees, planted too close to the foundation, can cause not only a lack of moisture but the tree roots can extend out a distance equal to the canopy of the tree branches. Periodic root pruning is required to prevent roots from extending under the foundation. An overabundance of water can cause as much damage as insufficient amount. One preventative step is the minimization of ponding water near the foundation. It is difficult to take water out of the soil, so the area around the foundation should slope away from the building. Also, the gutters should be kept clear of debris and the downspouts should drain at least three feet away from the foundation.

While all buildings move to some extent, the amount of movement can be controlled. The suggestions above can minimize much of the foundation movement that can damage interior and exterior walls, and ultimately the integrity of the building in general. More severe movement problems can be addressed with properly designed engineering solutions such as the installation of piers. For answers to your questions on foundation movement, do not hesitate to contact Ms. M. Jane Casey, P.E. of Aaron & Wright at 713-942-8980.

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