The lowest part of a building is the foundation. Shallow foundations or footings go about a meter deep into the soil. Concrete is poured into a trench where the structure is to be built. The hardened concrete transfers the wall weight to the soil or bedrock below. A deep foundation is typically used for large structures where the structure’s load is transferred through a weak top layer of soil to a stronger layer of subsoil or the bedrock below. Deep footings include drilled shafts, impact driven piles, helical piles, caissons, and earth stabilized columns. Foundations should have an adequate load capacity for little or no settlement. Differential settlement is when one part of a foundation settles more than another part. All you have to do is to look at the Leaning Tower of Pisa to understand differential settlement.
There are many signs of foundation problems that are not as blatant as those of the Leaning Tower of Pisa! For example, do you have doors and/or windows that will not open and close properly? Windows that are too snug to operate or doors that stick may indicate foundation problems. You may also have gaps around your doors and windows. Get a foundation inspection before you start replacing doors and windows; otherwise, you may be solving the wrong problem!
Several different problems may cause an uneven or sloping floor. Often this is a foundation problem, but it may also be deteriorating wood supports such as sills or simply improperly installed sub-floors or joists. Some homeowners just ignore the problem and say that the slanted floor adds character to the home. But these issues can lead to other problems so you ought to consult with a professional about what if anything should be done.
Another sign is cracks in the walls, cracks in the floor, cracked moldings, and cracks in exterior brick. If the soil under your foundation expands when wet and contracts when dry, your foundation could shift if part of the subsoil expands/contracts and the rest of the soil doesn’t. A related problem is that part of the soil was never compacted properly which can cause one part of your home to drop. Severe cases may involve sinkholes. We hear about sinkholes occurring in Florida that gobble up cars and even houses. These homeowners noticed strange depressions in their yards before the holes opened up.