There isn't a definitive answer to this question since it can vary greatly depending on the soil type, weather conditions, and other factors. However, in general, most foundations should be at least 18 inches deep. A foundation that is too shallow may not be able to support the weight of the structure, and a foundation that is too deep may not be cost effective. Additionally, if the soil underneath the foundation is unstable or wet, it may be necessary to go deeper in order to ensure safety. In some cases, such as when a building is being constructed over a burning stove, it may be necessary to excavate down to a depth of several feet in order to create a safe and stable foundation.
A foundation needs to be at least 8 inches deep, but 12 inches is preferable. The depth of the foundation depends on the weight of the building, the type of soil, and the distance between the building and the water table. For example, if you have a Burning Stove, you will need a deeper foundation because of the increased weight.
