What Are King County's Roof Snow Load Requirements?

Snow load isn’t the first thing most Federal Way homeowners think about when planning a reroof, but it’s part of the code requirements that apply regardless of how much snow the area actually sees in a typical year.

What the code requires

Washington State’s Residential Code includes specific requirements for wind and snow protection, and King County’s public rules specify that roof snow loads be calculated in accordance with SEAW’s “Snow Load Analysis for Washington,” a standardized engineering reference used across the state.

Why this applies even in a low-snow area

Federal Way and most of South King County see relatively modest snowfall — averaging around 5 inches a year — compared to higher-elevation parts of the state. The code requirement isn’t based on typical-year conditions, though; it’s a design-load calculation meant to ensure the structure can handle an unusual, more severe snow event without failing, which is why it applies uniformly across the county rather than being waived for lower-snowfall areas.

What this means for a reroof

For most straightforward like-for-like reroofs — replacing asphalt shingle with asphalt shingle, for example, without structural changes — the existing roof structure is generally assumed to already meet the applicable snow load requirement, since it was built to code originally. The calculation becomes more directly relevant when a project involves a heavier material upgrade or structural modifications, where the added weight needs to be verified against the design load.

Fastener and installation requirements

Beyond the structural load calculation itself, code includes specific installation requirements tied to snow and wind protection — for example, certain material types have minimum fastener counts specified for areas subject to snow, distinct from the base fastening pattern used in snow-free climates.

How we handle this

We factor code compliance, including any applicable snow-load-related requirements, into every reroof as part of the standard permit and installation process — it’s not an extra step we charge separately for, and it’s built into how we spec materials and fastening for your specific project.

The bottom line

You don’t need to calculate this yourself. It’s part of the standard code compliance that comes with a permitted reroof, and for most straightforward jobs it doesn’t change your material options or add meaningfully to project cost.