SnowLoadCheck

Walla Walla County, WA Roof Snow Load - 20 psf

Walla Walla County, WA roof snow load, translated

Moderate
20 psf

A typical heated home in Walla Walla 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.

Walla Walla County in numbers

Where Walla Walla County ranks

#1 of 10 Washington counties by design load, top 26% of 2,758 nationally - that's Walla Walla County's spot. That's 4 psf above Washington's own county-average design load of 16 psf.

FIPS 53071, population 62,068, centered near 46.2546°N 118.4804°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.

Walla Walla County: average annual snowfall

Walla Walla County sees about 6.5 in. of snow most winters, per the WALLA WALLA RGNL AP, WA US station's 1991-2020 NOAA normal. See the density guide.

Read this before you use Walla Walla 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.