Frost line depth in Sullivan County, IN

How deep the ground freezes in Sullivan County, IN

22 in. Dig to 22 in, just below the frost. Nearest NOAA station: Shakamak Sp, 10.5 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.