What are expansive soils?
Colorado is a rather unique area of the U.S. in that its geologic composition causes soils to expand. This can make it difficult to build homes in some areas of Colorado. Colorado builders sometimes use special foundations called structural wood sub-floors to counter the effects of expansive soils. However, these structural wood sub-floors can trap water or water vapor and allow mold to grow. This problem can be countered or eliminated by adequately ventilating the area beneath the structural wood sub-floor.
Expansive Soils are present throughout the world and are known in every U.S. state. Every year they cause billions of dollars in damage. The American Society of Civil Engineers estimates that 25% of all homes in the U.S. have some damage caused by expansive soils. In a typical year in the United States, they cause a greater financial loss to property owners than earthquakes, floods, hurricanes and tornadoes combined.
GENERAL ANSWER: Expansive soils are composed of clays that are usually generated over centuries as settlement to the bottom of bodies of water. They are usually high in salt and calcium contents. This was nature’s way of “sealing” the earthen bottom of a body of water to prevent it from leaking. Clay, in nature, is a sort of “grout”.
