Alexander County, IL Roof Snow Load - 15 psf
Alexander County, IL: your roof's ASCE 7 snow number, in plain English
Alexander County's roofs are built to hold 15 psf of snow, the ASCE 7-22 figure a permit reviewer checks first. 10.5 psf is what the ground-load formula alone gives; Alexander County's 15 psf low-slope minimum (§7.3.4) beats it, so that figure is the one that governs on flat and low-pitch roofs.
In depth, not weight: that's roughly 33 inches of fresh, light snow, 12 inches of old, settled snow, or as little as 3 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.
Alexander County, IL: quick facts
- Design roof snow load15 psf
- Ground snow load, ASCE 7 map15 psf
- National rank#1,613 of 2,758
- Illinois rank#100 of 102
- Population4,594
- Annual snowfall, NOAA normal7.2 in.
- FIPS17003
Alexander County by the numbers
Nationally that's #1,613 out of 2,758 rated counties, the top 58%; within Illinois alone, Alexander County ranks #100 of 102. Illinois counties average 19.3 psf; Alexander County runs 4.3 psf lower than that.
Alexander County, FIPS 17003, is home to 4,594 people near 37.1837°N 89.3495°W. Its 15 psf ground snow load figure is the map value; 15 psf is what a roof is actually designed for.
Alexander County's snowfall, most winters
7.2 in. a year: that's Alexander County's NOAA 1991-2020 snowfall normal, measured at GRAND CHAIN DAM 53, IL US (17 mi away). See the density guide.
Before you rely on Alexander County's number
Treat the Alexander 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. (How this figure is calculated.)