Warren County, IL Roof Snow Load - 20 psf
How much snow is too much for a roof in Warren County, IL?
20 psf: that's what ASCE 7-22 requires a typical heated home's roof in Warren County to carry. The physics-based figure alone would be 14 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. This is a meaningful design load - most modern-code homes handle it fine, though an addition, a carport or a flat-roofed section can be a weak spot.
Warren County in numbers
- Design roof snow load20 psf
- Ground snow load, ASCE 7 map20 psf
- National rank#1,008 of 2,758
- Illinois rank#60 of 102
- Population16,217
- Annual snowfall, NOAA normal25.6 in.
- FIPS17187
How Warren County compares
20 psf ranks #1,008 of 2,758 US counties with a mapped snow load (top 37%) - and #60 of 102 in Illinois. 19.3 psf is Illinois's typical county figure - Warren County beats it by 0.7 psf.
Population 16,217 (FIPS 17187), roughly 40.8504°N 90.6202°W. The 20 psf ground snow load ASCE 7-22 maps here becomes 20 psf once the code's own design factors are applied.
Typical snowfall in Warren County, IL
NOAA's 30-year normal for Warren County: 25.6 in. of snow a year, from the MONMOUTH, IL US station. (fresh vs. packed vs. ice explains why.)
What this Warren 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.
Warren 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. (How this figure is calculated.)