Frost line depth in Rappahannock County, VA
How deep the ground freezes in Rappahannock County, VA
17 in. Dig to 17 in, just below the frost. Nearest NOAA station: Sperryville, 3.7 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.