Franklin County, IL Roof Snow Load - 15 psf
How much snow is too much for a roof in Franklin County, IL?
15 psf: that's what ASCE 7-22 requires a typical heated home's roof in Franklin County to carry. Flat and low-pitch roofs in Franklin County are actually governed by ASCE 7's §7.3.4 minimum of 15 psf, not the 10.5 psf the ground-load formula alone would produce.
Picture it, not just weigh it: 33 in. if it's fresh powder, 12 in. once it settles, or a mere 3 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.
Franklin County, IL: quick facts
- Design roof snow load15 psf
- Ground snow load, ASCE 7 map15 psf
- National rank#1,410 of 2,758
- Illinois rank#91 of 102
- Population37,033
- Annual snowfall, NOAA normal9.8 in.
- FIPS17055
How Franklin County compares
15 psf ranks #1,410 of 2,758 US counties with a mapped snow load (top 51%) - and #91 of 102 in Illinois. That's 4.3 psf below Illinois's own county-average design load of 19.3 psf.
Population 37,033 (FIPS 17055), roughly 37.9919°N 88.9263°W. The 15 psf ground snow load ASCE 7-22 maps here becomes 15 psf once the code's own design factors are applied.
Typical snowfall in Franklin County, IL
NOAA's 30-year normal for Franklin County: 9.8 in. of snow a year, from the PLUMFIELD, IL US station. (fresh vs. packed vs. ice explains why.)
What this Franklin 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.
Franklin 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.