There are various things that can cause a foundation to develop problems, or start to move or settle. But the number one most common cause of all foundation problems is simply this – water. Excessive water can cause the underlying soil to swell up. Drought or lack of water can cause the soil to reduce in size. These actions alone do not cause a foundation problem if it occurs evenly around or under the entire house. It is when one side of a home has a shrinkage or swelling of soil due to water that there becomes a problem.
The differences in soil moisture levels can be caused by several things. Swelling soil is most like going to be the greater concern. Moisture gain can occur through such things as plumbing leaks and poor house drainage systems.
A loss of water in the soil is usually attributed to drought and is most common where the soil dries up rapidly which is along the perimeter of the foundation. This type of moisture unevenness can cause cracks to show up in the foundation of a house.
Another cause of soil moisture loss that can lead to foundation problems is nearby trees. The root systems of trees that are planted too close to the home can actually transpire underneath the house and dehydrate the soil below the home, causing shrinkage in the soil and potential foundational damage.
Water that freezes and expands underneath a home generates issues with the foundation as well. During the pouring process of a foundation, the humidity levels can be altered in the ground below. When temperatures drop and the water freezes irregularly, this can cause certain parts of the foundation to rise while the other parts do not. This, in turn, causes much strain on the foundation and ultimately becomes the precursor to foundational leaks, cracks and even larger foundation-related problems.
The type of soil used during the building process will also have an effect on the probability of the occurrence of shrinking and swelling. Some soils have within them certain organic components that are more prone to moisture fluctuations. For example, soils that have a high content of clay are generally more vulnerable to movement than soils with little to no clay in them. Keep in mind, there may be a trivial amount of movement occur that is harmless to the foundation.