Cass County, IL Roof Snow Load - 20 psf
Cass County, IL roof snow load, translated
A typical heated home in Cass County is designed to carry 20 pounds per square foot of snow on its roof, per ASCE 7-22. 14 psf is what the ground-load formula alone gives; Cass County's 20 psf low-slope minimum (§7.3.4) beats it, so that figure is the one that governs on flat and low-pitch roofs.
On a roof that means 44 in. of fresh snow, 16 in. once it packs down, or 4 in. of solid ice - three very different piles for the same load. 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.
Cass County in numbers
- Design roof snow load20 psf
- Ground snow load, ASCE 7 map20 psf
- National rank#1,062 of 2,758
- Illinois rank#73 of 102
- Population12,713
- Annual snowfall, NOAA normal19.3 in.
- FIPS17017
Where Cass County ranks
#73 of 102 Illinois counties by design load, top 39% of 2,758 nationally - that's Cass County's spot. 19.3 psf is Illinois's typical county figure - Cass County beats it by 0.7 psf.
FIPS 17017, population 12,713, centered near 39.9692°N 90.2457°W. ASCE 7's underlying ground snow load here is 20 psf before the code's exposure and importance factors bring it to the 20 psf design figure above.
Cass County: average annual snowfall
Cass County sees about 19.3 in. of snow most winters, per the VIRGINIA, IL US station's 1991-2020 NOAA normal. See the density guide.
Read this before you use Cass County's figure
The figure above assumes the case ASCE 7-22 treats as typical: a heated, ordinary-occupancy home on a partially exposed site. Change any of those - exposure, heating, roof pitch, occupancy category - and the real design number moves.
A building permit needs the number at your exact address, not the county average - the free ASCE 7 Hazard Tool returns that from your coordinates in about a minute and produces a PDF a plan reviewer will accept. See the methodology guide.