Foundation cracks can be a very serious situation, depending upon the type of material the foundation is composed of. After evaluating the cracks in the foundation, you can then determine the cause and what action to take. Some cracks are nothing to worry about, but others could be sign that there is structural damage that needs to be investigated by a professional as soon as possible.
Cracks are commonly found in concrete, poured concrete, and concrete block foundations. They are often caused by shrinkage, which can be distinguished by a crack that appears wider at the top and tapers inward toward the bottom. If the crack continues all the way to the floor, it may be a sign of structural damage and required further expert investigation. Cracks found in poured concrete foundations may be caused by bad conditions at time of pouring or poor mixing and don't require further investigation. Concrete blocks often shrink as they cure, causing cracks to form in the middle of the foundation and weakening the structure.
Foundation cracks found in brick walls are a serious matter that require immediate expert investigation. Bricks walls may absorb the moisture in the air, causing them to expand indefinitely, and eventually crack. Brick walls may also develop problems if the structure settles or there is an issue the support system. Cracks found in brick walls may result in the wall collapsing and causing serious damage.
Stone wall foundations may crack around the individual stones. This is usually caused by nearby blasting, damage from frost, or heavy traffic of load-bearing vehicles. Cracks in this type of foundation should be investigated immediately as there is a risk of structure collapse.
Diagonal cracks are often found around windowsills, over doors, around garages, and in the corners of buildings located in cold climates. They are usually a result of frost buildup and thermal expansion. If the cracks appear in a poured concrete foundation, and they are uniform is size and width, there shouldn't be any risk, as they are just shrinkage cracks. With other foundation materials, if the cracks continue to grow in length and width, there is a risk of structural damage and they should be investigated.
Horizontal foundation cracks found at the top level of the house may be caused by frost or heavily loaded vehicle traffic. If they are found at mid-level, they may be also be caused by heavily loaded vehicle traffic, hillsides, back-fill damage, or wet soil. Low-lying ones may be caused by earth loading or dislocation of masonry blocks.
Foundation cracks are a serious matter. While some are just cosmetic problems, others may cause the foundation to collapse. If there is any doubt about the seriousness of the cracks, consult an expert. It is better to be safe than sorry.