Wildland Urban Interface (WUI) Code Updates


Wildland-Urban Interface Codes (WUIC or WUI) reduce wildfire risks to people and property. Changes to code have been approved at the state level that may impact applications in Snohomish County that are not vested before March 15, 2024.

You can learn about the WUI code on this informative StoryMap created by the Washington State Department of Natural Resources, which provides background and links to more information.  


The Washington State Legislature has adopted the 2021 International Code Council (ICC) codes. The Wildland-Urban Interface Code is part of this code. The effective date for all building codes is March 15, 2024.

The WUI code adds fire protection standards to all structures based on proximity to areas with "vegetative fuels" that can contribute to wildfires even if permits are not required. The WUI code specifies ignition-resistant construction requirements for buildings, decks, detached structures and other components to protect against fire ignition from embers.

What's New?

Determining whether a project will have to comply with requirements of the WUI code can be done by consulting the WA Department of Natural Resources Map (link) or by consulting the Snohomish County PDS Map Portal and navigating to the WUI layer. (Click here for instructions on how to do this). While complex in administration and application, there are some items that when incorporated into projects go a long way towards compliance with the WUI code. Some of those are outlined below for reference.

Ventilation openings such as crawlspace and attic openings shall not exceed 144 square inches per vent. Openings are to be protected with maximum 1/4" metal mesh or be designed and approved to prevent flame or embers from entering the structure. Attic ventilation openings are no longer permitted in eave overhangs of soffits.

Exterior wall construction options include non-combustible materials, ignition resistant materials, 1-hour rated, heavy timber, or fire-retardant treated materials.

Class A roofing and valley flashing, if applicable, shall be metal.

Deck material options include heavy timber construction or approved alternatives per WAC 51-55-0500 Section 501.6. Heavy Timber minimum sizes for posts (6" X 6"), beams (6" X 8") and joists/star stringers (4" X8"). Walking surface materials have specific construction requirements, and decks less than 48" above finished grade shall be enclosed with screen material from grade to the underside of joists.



Q: What does 'vested' mean, and how do I know or make sure my project is vested?

  • A:  A project is deemed vested upon submittal of a complete permit application and required permit documents AND payment of application fees. When an application is received, PDS staff review the application for completeness and then invoice the applicant to pay the fees. Applicants should allow enough time for this process and submit applications they want to be vested prior to the adoption date. Submitting documents well in advance of the adoption date is recommended, as an application may not be vested until some time after the submission date to allow for time for staff review and payment of fees.

Q: I can't figure out if my project will be subject to this change using the resources above. What do I do?

  • A:  If you have a question about the applicability of the WUI code to your property, you may submit a question through the PDS Ask Permit Tech portal (Form Center • Snohomish County, WA • CivicEngage (snohomishcountywa.gov), come into the PDS Permit Center at 3000 Rockefeller Avenue, Everett, WA 98201 (2nd floor - Admin West, Robert J. Drewel Building) or call PDS at 425-388-3311.