Wisconsin Ground Snow Load: What the State Map Prints

Wisconsin draws its own ground snow load map, Figure 321.02 ZONE MAP FOR ROOF LOADS, through Department of Safety and Professional Services, Wisconsin Administrative Code ch. SPS 321, and the column on it is headed ROOF LOADS in the state’s own capitals. A roof load and a ground snow load are different quantities: the ground snow load is what a code keys to a place, and the roof load is what an engineer derives from it for one building. The two figures on that map are set out below in the state’s own wording, and neither is counted or compared as a ground snow load anywhere below. The Wisconsin map prints Zone 1 at 40 P.S.F. and Zone 2 at 30 P.S.F., and its own column heading calls those roof loads rather than ground snow loads, which are different quantities and not interchangeable.

Department of Safety and Professional Services: for a house the state's own two zone map governs; for commercial work the state's code points at the national standard's figure for the ground snow load. In its own words: “Ss = Ground snow load from IBC Figure 1608.2”

Wisconsin splits into zones or bands rather than counties, so the boundary that matters is drawn on the document itself.

Department of Safety and Professional Services adopts Uniform Dwelling Code, Chs. SPS 320-325 (one- and 2-family dwellings); International Building Code 2021 for commercial work, Chs. SPS 361-366 (Register November 2024 No. 827 (ch. SPS 321); International Building Code - 2021 (ch. SPS 361)). Wisconsin amended it rather than adopting it whole, and 22 states have done the same. The adopting rule reads: “SPS 320.01 Purpose. (1) The purpose of this code is to establish uniform statewide construction standards and inspection procedures for one- and 2-family dwellings and modular homes in accordance with the requirements of ss. 101.60 and 101.70, Stats.”

The Wisconsin map prints Zone 1 at 40 P.S.F. and Zone 2 at 30 P.S.F., and its own column heading calls those roof loads rather than ground snow loads, which are different quantities and not interchangeable. The two are different quantities: a ground snow load is what the published document keys to a place, and a roof load is what a structural calculation produces from it for one building. Department of Safety and Professional Services, Wisconsin Administrative Code ch. SPS 321 writes: “2. 'Snow loads.' Roofs shall be designed and constructed to support the minimum snow loads listed on the zone map. The loads shall be assumed to act vertically over the roof area projected upon a horizontal plane.”

A ground snow load is a weight per unit area and not a depth, and the two are joined only by the density of the snow on the day, which is why the published documents give the load and leave the depth out. Wet spring snow and dry January snow of the same depth are different weights on the same roof. Department of Safety and Professional Services works in loads for that reason, and so does every figure set out below.

The Wisconsin document itself is the place to look a town up, and what it prints is applied by Department of Safety and Professional Services. The document behind it is Figure 321.02 ZONE MAP FOR ROOF LOADS, published by Department of Safety and Professional Services, Wisconsin Administrative Code ch. SPS 321, read on September 23, 2026. It establishes the point this way: “2. 'Snow loads.' Roofs shall be designed and constructed to support the minimum snow loads listed on the zone map. The loads shall be assumed to act vertically over the roof area projected upon a horizontal plane.”

14 of 50: Connecticut, Indiana, Maryland, Massachusetts, Michigan, Minnesota, Montana, New Hampshire, New Jersey, North Carolina, Rhode Island, Utah, Vermont, Wisconsin. The other 36 split into 17 that adopt the national code without a snow amendment and 19 that leave every figure to a county or city building department. That is the single most useful fact about this subject and no one state's own website carries it.