Franklin County, WA Roof Snow Load - 10 psf
Franklin County, WA roof snow load, translated
A typical heated home in Franklin County is designed to carry 10 pounds per square foot of snow on its roof, per ASCE 7-22. Flat and low-pitch roofs in Franklin County are actually governed by ASCE 7's §7.3.4 minimum of 10 psf, not the 7 psf the ground-load formula alone would produce.
On a roof that means 22 in. of fresh snow, 8 in. once it packs down, or 2 in. of solid ice - three very different piles for the same load. A modest addition to standard roof loading. Ordinary residential construction handles this without extra bracing.
Franklin County in numbers
- Design roof snow load10 psf
- Ground snow load, ASCE 7 map10 psf
- National rank#1,716 of 2,758
- Washington rank#10 of 10
- Population101,238
- Annual snowfall, NOAA normal13.5 in.
- FIPS53021
Where Franklin County ranks
#10 of 10 Washington counties by design load, top 62% of 2,758 nationally - that's Franklin County's spot. Washington counties average 16 psf; Franklin County runs 6 psf lower than that.
FIPS 53021, population 101,238, centered near 46.5375°N 118.9039°W. ASCE 7's underlying ground snow load here is 10 psf before the code's exposure and importance factors bring it to the 10 psf design figure above.
Franklin County: average annual snowfall
Franklin County sees about 13.5 in. of snow most winters, per the HATTON 9 SE, WA US station's 1991-2020 NOAA normal. 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. (How this figure is calculated.)