SnowLoadCheck

Island County, WA Roof Snow Load - 15 psf

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

Moderate
15 psf

Island County's roofs are built to hold 15 psf of snow, the ASCE 7-22 figure a permit reviewer checks first. §7.3.4's low-slope minimum of 15 psf is what actually governs on a flat or low-pitch roof here - higher than the 10.5 psf the base ground-load formula gives.

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. This is a meaningful design load - most modern-code homes handle it fine, though an addition, a carport or a flat-roofed section can be a weak spot.

Island County, WA: quick facts

Island County by the numbers

Nationally that's #1,346 out of 2,758 rated counties, the top 49%; within Washington alone, Island County ranks #9 of 10. Washington counties average 16 psf; Island County runs 1 psf lower than that.

Island County, FIPS 53029, is home to 86,478 people near 48.1586°N 122.6706°W. Its 15 psf ground snow load figure is the map value; 15 psf is what a roof is actually designed for.

Island County's snowfall, most winters

2.5 in. a year: that's Island County's NOAA 1991-2020 snowfall normal, measured at COUPEVILLE 1 S, WA US (3.5 mi away). See the density guide.

Before you rely on Island County's number

Treat the Island 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.)