Foundation settlement and movement typically in St. Louis and all over Missouri is caused by building on expansive clay, improperly compacted fill soils, or improper maintenance around foundations.
Foundation failure in MO may occur because of a variety of causes. Sometimes root expansion can shift a foundation off its footings. Drought, freezing and extreme temperature changes are also concerns. Soil composition, moisture levels, and settlement are contributing factors. Fill soil that is washed away or that swells due to plumbing leaks or other sources of excess moisture can cause shifting, instability, and cracking in your foundation.
Observing soil moisture changes in the St. Louis area around your foundation is possible, but what about under it? Moisture can move from outside to under your foundation through a property of soils known as suction. Soil suction is similar to placing just a corner of a dry, compressed sponge in contact with a puddle of water. In a short time, the sponge has drawn water throughout itself and grown in volume.
While a water source is present, the sponge will continue to absorb water until it is saturated. If the water source is cut-off, then water already in the sponge will distribute itself evenly, but the sponge will not reach saturation.
Water can move horizontally and vertically through the soils under your foundation in a similar manner. As clay-filled soils draw water to themselves, they too grow in volume (swell or heave) causing your foundation to move. Drying outside your foundation reverses the process. The moist soils will lose volume (shrink) as soil moisture moves out from under your foundation causing the foundation to settle. Shrinking and swelling soil motions can lead to damaging your foundation and structure. Uniform changes in soil moisture are less damaging to your structure than localized changes. We know the soils vary from location to location. For example, Jefferson City may have more rock based soils while Warrenton would hold more clay soils.