Cleveland's frost line is 42 inches, according to the city's building code. The frost line is measured to determine how deep footings must be for newly constructed buildings. Structures built too far above the frost line may suffer damage from frost heave.
Frost heave happens when groundwater freezes too close to the bottom of a foundation. As the frozen soil expands, it exerts upward pressure on the structure and eventually displaces it. Because the pressure is uneven, some sections might remain unaffected, while others experience extreme force, and catastrophic damage to the slab may result.
Although Cleveland's frost line is 42 inches, the building code allows for shallower construction in some cases. Footings for one- and two-family homes built on soil subject to frost heave need only be 36 inches deep, for example, and single story building footings need only be as deep as necessary for structural support, unless the buildings are subject to heave.
Another potential danger of building too close to the frost line is that it leaves unprotected plumbing vulnerable to freezing.
During the construction process, the contractor must protect footings and foundations against freezing until the area is filled with soil, or the structure itself is far enough along to protect the footings and foundation against freezing.