Frost line depth in Manassas city, VA

How deep the ground freezes in Manassas city, VA

no frost in a normal winter. Dig to 12 in, the 12 in code minimum. Nearest NOAA station: Manassas, 1.1 mi.

Your building department sets the legal frost line depth (IRC Table R301.2(1)); footings must go below it (R403.1.4.1). Call them before you dig.