SnowLoadCheck

Grundy County, IL Roof Snow Load - 20 psf

What ASCE 7 says about snow load in Grundy County

Moderate
20 psf

That's Grundy County's design roof snow load per ASCE 7-22, for a typical heated single-family home - the number a permit reviewer starts from. §7.3.4's low-slope minimum of 20 psf is what actually governs on a flat or low-pitch roof here - higher than the 14 psf the base ground-load formula gives.

Converted to something you can actually eyeball on a roof: about 44 in. of fresh powder, 16 in. once it settles and packs down, or just 4 in. if it's turned to 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.

Got real snow on a Grundy County roof right now?

in. of

Grundy County at a glance

Where Grundy County's figure sits nationally

Out of 2,758 rated US counties, Grundy County sits at #726, the top 26% nationally - #24 of 102 within Illinois. That's 0.7 psf above Illinois's own county-average design load of 19.3 psf.

Near 41.2924°N 88.4011°W, FIPS 17063: Grundy County counts 53,835 residents and a 20 psf map value, which the code's own factors turn into 20 psf.

How much it actually snows in Grundy County

Most winters bring Grundy County roughly 24.7 in. of snow - NOAA's normal at MORRIS 1 NW, IL US, 5.7 mi off. (fresh vs. packed vs. ice explains why.)

Read this before you rely on it

Grundy County's number above is ASCE 7-22's default case, not a custom calculation: ordinary residential occupancy, heated, sited on ground that's neither fully sheltered nor fully exposed. Any one of those changing - pitch, exposure, heating, occupancy - moves the real figure.

Nothing here substitutes for an address-level number. Get one free, in about a minute, from the ASCE 7 Hazard Tool using your own coordinates rather than Grundy County's county-wide figure. (How this figure is calculated.)