Franklin County, MO Roof Snow Load - 20 psf
Franklin County, MO roof snow load, translated
A typical heated home in Franklin 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. A meaningful design load. Most homes built to modern code handle it, but additions, carports, and flat-roofed sections are worth a second look.
Franklin County at a glance
- Design roof snow load20 psf
- Ground snow load, ASCE 7 map20 psf
- National rank#643 of 2,758
- Missouri rank#10 of 115
- Population107,256
- Annual snowfall, NOAA normal13.5 in.
- FIPS29071
Where Franklin County ranks
#10 of 115 Missouri counties by design load, top 23% of 2,758 nationally - that's Franklin County's spot. That's 1.4 psf above Missouri's own county-average design load of 18.6 psf.
FIPS 29071, population 107,256, centered near 38.413°N 91.0728°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.
Franklin County: average annual snowfall
Franklin County sees about 13.5 in. of snow most winters, per the WELDON SPRING NWS, MO US station's 1991-2020 NOAA normal. Worth noting: the nearest station reporting snowfall normals sits 28.9 mi from Franklin County's center, so treat this as a regional figure rather than an exact one. See the density guide.
Read this before you use Franklin 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. Details: the calculation guide.