The frost line in Maryland is 30 inches deep. The frost line is the depth in the ground that ground water will freeze. It is also referred to as the freezing depth or frost depth.
A 30-inch frost line means that a building's foundations must be properly anchored at least 30 inches below ground. Because ground water freezes and swells, the foundation can be compromised if it is not installed at an adequate depth. To protect a building from damage, its foundation must be able to withstand the changing temperatures associated with Maryland's winters, as well as combat the high water table and frequent rainfall in the area.
The footings of the foundation are what supports the entire building. These must be constructed below the frost line, so the slope and elevation of the land must be considered. A stepped footing system takes those slopes into account and ensures that all the footings remain below the frost line. The type of soil is also an important factor in building a safe, well-established foundation. Some soils in the Maryland area are more susceptible to ice formation, making the frost line depth even more crucial in the footing, foundation and building process. Local building code guidelines should be referenced when constructing a new structure in Maryland.