November 11, 2009
This term indicates a method of building on a concrete foundation that goes into the ground only slightly below the frost line. The frost line is a point in the ground below which the ground never freezes. As you might guess, the depth of the frost line depends on many variables besides degree of northern latitude, such as groundwater, shade conditions, and composition of the subsoil (e.g., sand never freezes). In the coldest parts of the United States, the frost line is a maximum of about four feet down. Most people excavate at least that deeply to be sure of avoiding the frost heaves that can ruin a house’s frame. Point is that you have to make judgments about soundness on a house-by-house basis.
So what should you look for?
