What Are Snohomish County's Wind Speed and Snow Load Requirements for a Roof?

Snohomish County’s building code sets specific structural requirements for wind and snow load — real numbers that affect how a roof should actually be built here, not just paperwork.

The wind speed requirement

For prescriptive structural design under the International Residential Code (IRC), Snohomish County requires a 110 mph design wind speed. If a project uses IBC-based structural design instead, the applicable wind map under the currently adopted IBC applies. Either way, the wind exposure category — how directly a specific site is exposed to wind, versus sheltered by terrain or structures — is determined on a site-by-site basis.

Why this matters more on some Everett properties than others

Everett sits directly on Puget Sound at Port Gardner, with no sheltering high ground to the west. A waterfront-facing or bluff-lot property here sits at a meaningfully higher wind exposure category than an inland lot surrounded by other buildings and mature trees — even though both fall under the same county code minimum. We assess actual site exposure, not just the code floor, when specifying underlayment and fastening.

The snow load requirement

Snohomish County requires a minimum 25 psf (pounds per square foot) roof snow load — lower than what Cascade-foothill communities require, since Everett’s low elevation and coastal location see far less snow accumulation than higher-elevation parts of the county. This is a baseline structural minimum, not a reflection of how often it actually snows in a given year.

What this means for your roof, practically

• Underlayment — high-wind-rated synthetic underlayment, not a standard-grade product, especially on wind-exposed lots
• Fastening pattern — matched to the site’s actual exposure category, following manufacturer wind-uplift specifications
• Flashing — properly sealed at every penetration, since wind-driven rain finds gaps that gravity-fed rain wouldn’t
• Material choice — while not strictly mandated by wind speed alone, higher-wind-rated materials (architectural shingle over 3-tab, for instance) make more sense on exposed sites

The bottom line

We install to Snohomish County’s actual requirements, adjusted for your specific property’s real exposure — not a one-size-fits-all national-average spec. Call for a free inspection and we’ll assess your lot’s actual wind exposure as part of the quote.