Massac County, IL Roof Snow Load - 15 psf
Massac County, IL: your roof's ASCE 7 snow number, in plain English
Massac County's roofs are built to hold 15 psf of snow, the ASCE 7-22 figure a permit reviewer checks first. 10.5 psf is what the ground-load formula alone gives; Massac County's 15 psf low-slope minimum (§7.3.4) beats it, so that figure is the one that governs on flat and low-pitch roofs.
In depth, not weight: that's roughly 33 inches of fresh, light snow, 12 inches of old, settled snow, or as little as 3 inches of solid ice - snow that heavy is rare here but ice from a freeze-thaw cycle adds up far faster than the depth suggests. 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.
Massac County at a glance
- Design roof snow load15 psf
- Ground snow load, ASCE 7 map15 psf
- National rank#1,512 of 2,758
- Illinois rank#94 of 102
- Population13,627
- Annual snowfall, NOAA normal3.1 in.
- FIPS17127
Massac County by the numbers
Nationally that's #1,512 out of 2,758 rated counties, the top 55%; within Illinois alone, Massac County ranks #94 of 102. 19.3 psf is Illinois's typical county figure - Massac County comes in 4.3 psf under it.
Massac County, FIPS 17127, is home to 13,627 people near 37.2161°N 88.7057°W. Its 15 psf ground snow load figure is the map value; 15 psf is what a roof is actually designed for.
Massac County's snowfall, most winters
3.1 in. a year: that's Massac County's NOAA 1991-2020 snowfall normal, measured at BROOKPORT DAM 52, IL US (6.8 mi away). See the density guide.
Before you rely on Massac County's number
Treat the Massac County figure as a starting point, not a final answer: it assumes standard occupancy, a heated structure and a moderately sheltered site, per ASCE 7-22's own defaults. Exposed terrain, an unheated building or a steeper roof all shift the real number.
For a real application, skip the county number and go straight to the ASCE 7 Hazard Tool - enter your coordinates and it returns a site-specific figure a plan reviewer will recognize. See the methodology guide.