Wisconsin

Statewide summary — confirm with your building department before designing

AUDIT 2026-08-12 (physical design data pass). Wisconsin has a genuine mandatory statewide one- and two-family code and it does publish a statewide snow number, but that number is a ROOF load, not a ground snow load, so the ground snow min and max columns on this row remain null. This is a deliberate refusal to convert, not a failed lookup, and the distinction matters enough to state plainly before anything else on this row. What Wisconsin actually publishes: SPS 321.02(1)(b)2, in the Uniform Dwelling Code, provides that roofs shall be designed and constructed to support the minimum snow loads listed on the zone map, and that the loads shall be assumed to act vertically over the roof area projected upon a horizontal plane. The zone map is Figure 321.02, headed ZONE MAP FOR ROOF LOADS. It is a raster county map with no text layer; it was rendered and read directly. It divides the state into two zones with a legend giving Zone 1 at 40 psf and Zone 2 at 30 psf. Zone 1 is the northern part of the state and Zone 2 the southern, the boundary running roughly from the Mississippi at Pierce and Pepin counties east and south of Eau Claire, Clark, Wood, Portage and Waupaca, then east to Brown county and Green Bay, so that Milwaukee, Madison, Racine, Kenosha, La Crosse, Oshkosh and Fond du Lac fall in the 30 psf zone and Wausau, Eau Claire, Superior, Rhinelander and Green Bay fall in the 40 psf zone. Those two figures, 30 and 40, are the whole of Wisconsin published snow legislation for dwellings, and they are roof loads. Converting them back to ground loads would require assumptions about exposure, thermal and slope factors that Wisconsin does not supply, and doing so would be interpolation, so it was not done. Storing 30 and 40 in the ground snow columns would also make this row silently incomparable with states such as Michigan and Minnesota, whose columns hold true ground loads, so the columns are left null. Wisconsin publishes no ground snow load anywhere else either, and this was checked rather than assumed. On the commercial side, SPS 362.1603 requires only that the ground snow load Pg be indicated on the construction documents, and SPS 362.1608, which supplies Wisconsin own unbalanced snow load formula, defines its Ss term as the ground snow load from IBC Figure 1608.2. That is the national model-code map, unamended, with no Wisconsin values substituted. So for commercial work Wisconsin points at the model map and for dwellings it publishes roof zones; at no point does the state assign a ground snow load to any Wisconsin county. Frost depth 48 inches is now confirmed against adopted text and is no longer unverified. SPS 321.16(1)(a) provides that footings and foundations, including those for landings and stoops, shall be placed below the frost penetration level or at least 48 inches below adjacent grade, whichever is deeper. The important word is whichever: 48 inches is a statewide floor, not a statewide answer, and in the northern counties the actual frost penetration level governs and is deeper. The earlier note on this row was right that 48 inches protects Milwaukee and Madison and not Superior or Rhinelander, and the rule text is the reason why. SPS 321.16(2) allows frost protected shallow foundations designed to ASCE 32, bearing directly on cleaned bedrock at less than 48 inches under stated conditions, and exempts footings under window areaways and most ramp footings. Wind speed 105 mph is not a Wisconsin figure and remains unverified. SPS 321.02(1)(c) does not state a wind speed at all; it requires that dwellings withstand either a horizontal and uplift pressure of 20 pounds per square foot acting over the surface area, or the wind loads determined in accordance with ASCE 7-05, with a note that ASCE 7-05 allows substantial reduction from the 20 psf figure. A designer reading this row should understand that Wisconsin regulates dwelling wind loading as a pressure, not as a mph contour, and that the 105 here comes from the national map rather than from the state. Ground snow load 40 psf is left on the row but should be read with care: 40 psf is Wisconsin northern zone ROOF load, and it is not published by Wisconsin as a ground load for anywhere. PRIOR AUDIT NOTE (still accurate as to the seismic determination; its remark that the remaining values could not be confirmed against the Uniform Dwelling Code is now partly superseded, since frost depth and the roof snow zones are confirmed above): No value on this row was changed by this audit. Seismic design category A is confirmed and is the lowest hazard in this group: the USGS ASCE 7-16 design maps service, at Site Class D and Risk Category II under the IRC single parameter method, returns short period design accelerations of 0.080 g at Milwaukee, 0.079 g at Madison and 0.054 g at Green Bay, far inside category A with no part of the state approaching the threshold. Termite risk of slight corresponds to the IRC slight to moderate band, which covers southern Wisconsin where most of the population lives; the northern counties fall in the none to slight band. The remaining values could not be confirmed against Wisconsin's adopted Uniform Dwelling Code provisions and are unverified. Wind speed of 105 mph sits between the ASCE 7-16 contours and is reported rather than adjusted, because the project has not settled whether to round up to the next contour. Frost depth of 48 inches is the usual southern Wisconsin figure but the northern counties commonly require 60 inches or more, so this value protects Milwaukee and Madison and not Superior or Rhinelander. Ground snow load of 40 psf runs above what Milwaukee and Madison normally carry, nearer 30 psf, and below what the northern counties carry, so it over builds the two largest metropolitan areas while still falling short in the north. Winter design temperature derives from ASHRAE data that no Wisconsin jurisdiction was found to have adopted into its own table, so it remains unestablished. IRC Table R301.2 is filled in by the local jurisdiction and the number that governs your lot is the one your building official has adopted, not the one on this row. Source: https://earthquake.usgs.gov/ws/building-codes/