Shelby County, MO Roof Snow Load - 20 psf
Shelby County, MO roof snow load, translated
A typical heated home in Shelby County is designed to carry 20 pounds per square foot of snow on its roof, per ASCE 7-22. Flat and low-pitch roofs in Shelby 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.
On a roof that means 44 in. of fresh snow, 16 in. once it packs down, or 4 in. of solid ice - three very different piles for the same load. 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.
Shelby County at a glance
- Design roof snow load20 psf
- Ground snow load, ASCE 7 map20 psf
- National rank#1,195 of 2,758
- Missouri rank#75 of 115
- Population5,926
- Annual snowfall, NOAA normal17.8 in.
- FIPS29205
Where Shelby County ranks
#75 of 115 Missouri counties by design load, top 43% of 2,758 nationally - that's Shelby County's spot. That's 1.4 psf above Missouri's own county-average design load of 18.6 psf.
FIPS 29205, population 5,926, centered near 39.7975°N 92.0887°W. ASCE 7's underlying ground snow load here is 20 psf before the code's exposure and importance factors bring it to the 20 psf design figure above.
Shelby County: average annual snowfall
Shelby County sees about 17.8 in. of snow most winters, per the STEFFENVILLE, MO US station's 1991-2020 NOAA normal. See the density guide.
Read this before you use Shelby County's figure
The figure above assumes the case ASCE 7-22 treats as typical: a heated, ordinary-occupancy home on a partially exposed site. Change any of those - exposure, heating, roof pitch, occupancy category - and the real design number moves.
A building permit needs the number at your exact address, not the county average - the free ASCE 7 Hazard Tool returns that from your coordinates in about a minute and produces a PDF a plan reviewer will accept. (How this figure is calculated.)