Pettis County, MO Roof Snow Load - 20 psf
Pettis County, MO roof snow load, translated
A typical heated home in Pettis County is designed to carry 20 pounds per square foot of snow on its roof, per ASCE 7-22. 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.
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. Modern-code homes carry a load like this without issue; an older addition, a carport, or any flat-roofed section is where it is worth checking first.
Pettis County in numbers
- Design roof snow load20 psf
- Ground snow load, ASCE 7 map20 psf
- National rank#765 of 2,758
- Missouri rank#20 of 115
- Population43,791
- Annual snowfall, NOAA normal18.4 in.
- FIPS29159
Where Pettis County ranks
#20 of 115 Missouri counties by design load, top 28% of 2,758 nationally - that's Pettis County's spot. 18.6 psf is Missouri's typical county figure - Pettis County beats it by 1.4 psf.
FIPS 29159, population 43,791, centered near 38.7274°N 93.2852°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.
Pettis County: average annual snowfall
Pettis County sees about 18.4 in. of snow most winters, per the COLE CAMP 3NW, MO US station's 1991-2020 NOAA normal. See the density guide.
Read this before you use Pettis 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. See the methodology guide.