Putnam County, IL Roof Snow Load - 20 psf
How much snow is too much for a roof in Putnam County, IL?
20 psf: that's what ASCE 7-22 requires a typical heated home's roof in Putnam 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. A meaningful design load. Most homes built to modern code handle it, but additions, carports, and flat-roofed sections are worth a second look.
Putnam County at a glance
- Design roof snow load20 psf
- Ground snow load, ASCE 7 map20 psf
- National rank#1,205 of 2,758
- Illinois rank#85 of 102
- Population5,633
- Annual snowfall, NOAA normal18.4 in.
- FIPS17155
How Putnam County compares
20 psf ranks #1,205 of 2,758 US counties with a mapped snow load (top 44%) - and #85 of 102 in Illinois. That's 0.7 psf above Illinois's own county-average design load of 19.3 psf.
Population 5,633 (FIPS 17155), roughly 41.199°N 89.2983°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 Putnam County, IL
NOAA's 30-year normal for Putnam County: 18.4 in. of snow a year, from the VARNA, IL US station. (fresh vs. packed vs. ice explains why.)
What this Putnam 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.
Putnam 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.