Boone County, IL Roof Snow Load - 20 psf
How much snow is too much for a roof in Boone County, IL?
20 psf: that's what ASCE 7-22 requires a typical heated home's roof in Boone County to carry. 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.
Picture it, not just weigh it: 44 in. if it's fresh powder, 16 in. once it settles, or a mere 4 in. if it's ice. Modern-code homes carry a load like this without issue; an older addition, a carport, or any flat-roofed section is where it is worth checking first.
Boone County, IL: quick facts
- Design roof snow load20 psf
- Ground snow load, ASCE 7 map25 psf
- National rank#729 of 2,758
- Illinois rank#25 of 102
- Population53,313
- Annual snowfall, NOAA normal32.6 in.
- FIPS17007
How Boone County compares
20 psf ranks #729 of 2,758 US counties with a mapped snow load (top 26%) - and #25 of 102 in Illinois. Illinois counties average 19.3 psf; Boone County runs 0.7 psf higher than that.
Population 53,313 (FIPS 17007), roughly 42.319°N 88.8243°W. The 25 psf ground snow load ASCE 7-22 maps here becomes 20 psf once the code's own design factors are applied.
Typical snowfall in Boone County, IL
NOAA's 30-year normal for Boone County: 32.6 in. of snow a year, from the BELVIDERE, IL US station. (fresh vs. packed vs. ice explains why.)
What this Boone County figure assumes
This is a county-level reference figure for a typical heated home built to Risk Category II (ordinary residential), on a partially exposed lot - the assumptions ASCE 7-22 itself treats as the default case. A steeper roof, a fully exposed hilltop lot, an unheated structure, or a higher risk category all change the actual number.
Boone County's permit office wants an address-specific figure, not this county average - the ASCE 7 Hazard Tool is free, takes under a minute, and outputs a PDF most reviewers accept. See the methodology guide.