Carroll County, IL Roof Snow Load - 20 psf
How much snow is too much for a roof in Carroll County, IL?
20 psf: that's what ASCE 7-22 requires a typical heated home's roof in Carroll County to carry. ASCE 7's low-slope-roof minimum (§7.3.4) raises the governing figure to 20 psf - higher than the 17.5 psf the ground-load formula alone would give, and the code says use the larger one.
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.
Carroll County, IL: quick facts
- Design roof snow load20 psf
- Ground snow load, ASCE 7 map25 psf
- National rank#1,017 of 2,758
- Illinois rank#62 of 102
- Population15,444
- Annual snowfall, NOAA normal33.4 in.
- FIPS17015
How Carroll County compares
20 psf ranks #1,017 of 2,758 US counties with a mapped snow load (top 37%) - and #62 of 102 in Illinois. That's 0.7 psf above Illinois's own county-average design load of 19.3 psf.
Population 15,444 (FIPS 17015), roughly 42.0709°N 89.9242°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 Carroll County, IL
NOAA's 30-year normal for Carroll County: 33.4 in. of snow a year, from the MT CARROLL, IL US station. (fresh vs. packed vs. ice explains why.)
What this Carroll 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.
Carroll 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. Details: the calculation guide.