SnowLoadCheck

St. Louis County, MO Roof Snow Load - 20 psf

How much snow is too much for a roof in St. Louis County, MO?

Moderate
20 psf

20 psf: that's what ASCE 7-22 requires a typical heated home's roof in St. Louis 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. 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.

St. Louis County, MO: quick facts

How St. Louis County compares

20 psf ranks #510 of 2,758 US counties with a mapped snow load (top 18%) - and #1 of 115 in Missouri. 18.6 psf is Missouri's typical county figure - St. Louis County beats it by 1.4 psf.

Population 992,929 (FIPS 29189), roughly 38.6404°N 90.4455°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 St. Louis County, MO

NOAA's 30-year normal for St. Louis County: 10.2 in. of snow a year, from the VALLEY PARK, MO US station. (fresh vs. packed vs. ice explains why.)

What this St. Louis 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.

St. Louis 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.