SnowLoadCheck

Thurston County, WA Roof Snow Load - 15 psf

Thurston County, WA: your roof's ASCE 7 snow number, in plain English

Moderate
15 psf

Thurston County's roofs are built to hold 15 psf of snow, the ASCE 7-22 figure a permit reviewer checks first. 10.5 psf is what the ground-load formula alone gives; Thurston County's 15 psf low-slope minimum (§7.3.4) beats it, so that figure is the one that governs on flat and low-pitch roofs.

In depth, not weight: that's roughly 33 inches of fresh, light snow, 12 inches of old, settled snow, or as little as 3 inches of solid ice - snow that heavy is rare here but ice from a freeze-thaw cycle adds up far faster than the depth suggests. A meaningful design load. Most homes built to modern code handle it, but additions, carports, and flat-roofed sections are worth a second look.

Thurston County at a glance

Thurston County by the numbers

Nationally that's #1,319 out of 2,758 rated counties, the top 48%; within Washington alone, Thurston County ranks #6 of 10. That's 1 psf below Washington's own county-average design load of 16 psf.

Thurston County, FIPS 53067, is home to 302,912 people near 46.9358°N 122.8302°W. Its 15 psf ground snow load figure is the map value; 15 psf is what a roof is actually designed for.

Thurston County's snowfall, most winters

3.9 in. a year: that's Thurston County's NOAA 1991-2020 snowfall normal, measured at OLYMPIA AP, WA US (4.3 mi away). See the density guide.

Before you rely on Thurston County's number

Treat the Thurston County figure as a starting point, not a final answer: it assumes standard occupancy, a heated structure and a moderately sheltered site, per ASCE 7-22's own defaults. Exposed terrain, an unheated building or a steeper roof all shift the real number.

For a real application, skip the county number and go straight to the ASCE 7 Hazard Tool - enter your coordinates and it returns a site-specific figure a plan reviewer will recognize. (How this figure is calculated.)