DuPage County, IL Roof Snow Load - 20 psf
DuPage County, IL: your roof's ASCE 7 snow number, in plain English
DuPage County's roofs are built to hold 20 psf of snow, the ASCE 7-22 figure a permit reviewer checks first. The physics-based figure alone would be 17.5 psf, but ASCE 7's own low-slope minimum (§7.3.4) sets a floor of 20 psf for flat and low-pitch roofs here, which is the number that actually governs.
In depth, not weight: that's roughly 44 inches of fresh, light snow, 16 inches of old, settled snow, or as little as 4 inches of solid ice - snow that heavy is rare here but ice from a freeze-thaw cycle adds up far faster than the depth suggests. A meaningful design load. Most homes built to modern code handle it, but additions, carports, and flat-roofed sections are worth a second look.
DuPage County at a glance
- Design roof snow load20 psf
- Ground snow load, ASCE 7 map25 psf
- National rank#514 of 2,758
- Illinois rank#2 of 102
- Population937,142
- Annual snowfall, NOAA normal42.3 in.
- FIPS17043
DuPage County by the numbers
Nationally that's #514 out of 2,758 rated counties, the top 19%; within Illinois alone, DuPage County ranks #2 of 102. 19.3 psf is Illinois's typical county figure - DuPage County beats it by 0.7 psf.
DuPage County, FIPS 17043, is home to 937,142 people near 41.8521°N 88.086°W. Its 25 psf ground snow load figure is the map value; 20 psf is what a roof is actually designed for.
DuPage County's snowfall, most winters
42.3 in. a year: that's DuPage County's NOAA 1991-2020 snowfall normal, measured at OAK BROOK 2W, IL US (5.9 mi away). See the density guide.
Before you rely on DuPage County's number
Treat the DuPage County figure as a starting point, not a final answer: it assumes standard occupancy, a heated structure and a moderately sheltered site, per ASCE 7-22's own defaults. Exposed terrain, an unheated building or a steeper roof all shift the real number.
For a real application, skip the county number and go straight to the ASCE 7 Hazard Tool - enter your coordinates and it returns a site-specific figure a plan reviewer will recognize. See the methodology guide.