Lake County, IL Roof Snow Load - 20 psf
How much snow is too much for a roof in Lake County, IL?
20 psf: that's what ASCE 7-22 requires a typical heated home's roof in Lake 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. 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.
Lake County at a glance
- Design roof snow load20 psf
- Ground snow load, ASCE 7 map25 psf
- National rank#523 of 2,758
- Illinois rank#3 of 102
- Population718,604
- Annual snowfall, NOAA normal33.6 in.
- FIPS17097
How Lake County compares
20 psf ranks #523 of 2,758 US counties with a mapped snow load (top 19%) - and #3 of 102 in Illinois. 19.3 psf is Illinois's typical county figure - Lake County beats it by 0.7 psf.
Population 718,604 (FIPS 17097), roughly 42.186°N 87.8059°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 Lake County, IL
NOAA's 30-year normal for Lake County: 33.6 in. of snow a year, from the CHICAGO BOTANIC GARDEN, IL US station. (fresh vs. packed vs. ice explains why.)
What this Lake 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.
Lake 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.