SnowLoadCheck

Jefferson County, MO Roof Snow Load - 20 psf

What ASCE 7 says about snow load in Jefferson County

Moderate
20 psf

That's Jefferson County's design roof snow load per ASCE 7-22, for a typical heated single-family home - the number a permit reviewer starts from. ASCE 7's low-slope-roof minimum (§7.3.4) raises the governing figure to 20 psf - higher than the 14 psf the ground-load formula alone would give, and the code says use the larger one.

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.

Jefferson County, MO: quick facts

Where Jefferson County's figure sits nationally

Out of 2,758 rated US counties, Jefferson County sits at #577, the top 21% nationally - #6 of 115 within Missouri. 18.6 psf is Missouri's typical county figure - Jefferson County beats it by 1.4 psf.

Near 38.2576°N 90.5437°W, FIPS 29099: Jefferson County counts 231,888 residents and a 20 psf map value, which the code's own factors turn into 20 psf.

How much it actually snows in Jefferson County

Most winters bring Jefferson County roughly 9.2 in. of snow - NOAA's normal at FESTUS, MO US, 8.1 mi off. (fresh vs. packed vs. ice explains why.)

Read this before you rely on it

Jefferson 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 Jefferson County's county-wide figure. (How this figure is calculated.)