Clay soils also may be known as expansive soils, swelling soils, adobe or caliche soils. When soil containing high concentrations of clay becomes wet, it expands. When it dries, it contracts and can crack. If the soil underneath your home’s foundation is clay or expansive, it can create several foundation problems including foundation cracks and shifting.
The clay minerals in expansive soils have intense absorption power for water molecules. According to the Mineralogical Society, “The strong interaction between clays and water results from the high specific surface area and structure of the clay minerals and from the polar nature of the water molecule.”
Wet, swollen clay in the soil can influence the soil’s behavior and movement. Some clay minerals such as smectite (found in soils in Colorado and Texas) tend to swell more than other clay types. However, all clay soils will expand when absorbing water. Improperly prepared soil beneath a foundation or footings that have not been sunk deep enough can be affected by clay soil expansion, heaving the soil upward towards the concrete. This expansion and eventual contraction (shrinkage) after drying contributes to foundation cracks and other problems.
Some areas of the country are more prone to foundation damage caused by expansive soils. Colorado, Texas and Kansas are just three states with homes exhibiting signs of foundation problems due to clay soil issues. This type of soil expansion and contraction is similar to frost heave seen in colder, northern areas of the country.
Not sure if your home sits upon clay soils? There are a couple of ways to determine if your home’s foundation rests on expansive soils. After several days without precipitation, go out and look at the ground around your home. In dry seasons, clay soils will exhibit deep cracks formed in a polygonal-type shape or pattern. You also can consult with a qualified foundation repair specialist who works with clay soils and foundation problems.
Drought conditions also cause deep cracking of expansive soils and can contribute to house foundation problems. If you see signs of foundation problems, it is recommended you contact a specialist for a foundation inspection