Lewis County, MO Roof Snow Load - 20 psf
How much snow is too much for a roof in Lewis County, MO?
20 psf: that's what ASCE 7-22 requires a typical heated home's roof in Lewis County to carry. Flat and low-pitch roofs in Lewis County are actually governed by ASCE 7's §7.3.4 minimum of 20 psf, not the 14 psf the ground-load formula alone would produce.
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.
Lewis County in numbers
- Design roof snow load20 psf
- Ground snow load, ASCE 7 map20 psf
- National rank#1,108 of 2,758
- Missouri rank#61 of 115
- Population9,852
- Annual snowfall, NOAA normal17.8 in.
- FIPS29111
How Lewis County compares
20 psf ranks #1,108 of 2,758 US counties with a mapped snow load (top 40%) - and #61 of 115 in Missouri. Missouri counties average 18.6 psf; Lewis County runs 1.4 psf higher than that.
Population 9,852 (FIPS 29111), roughly 40.0846°N 91.7288°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 Lewis County, MO
NOAA's 30-year normal for Lewis County: 17.8 in. of snow a year, from the STEFFENVILLE, MO US station. (fresh vs. packed vs. ice explains why.)
What this Lewis 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.
Lewis 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.