State Building Code. 
The State Building Code (Code) establishes minimum performance standards and requirements for construction and construction materials in the state, consistent with accepted standards of engineering, fire, and life safety.  The Code comprises a number of model codes and standards, developed and published by international and national organizations, which are adopted by reference in the State Building Code Act (Act).  Model codes and standards adopted in the Act include the International Building Code, International Residential Code, the International Mechanical Code, the International Fire Code, and the Uniform Plumbing Code Standards. 
 
The State Building Code Council (Council) is responsible for adopting, amending, and maintaining as appropriate the model codes and standards adopted by reference in the Act.  Amendments to the model codes and standards adopted by the Council are codified in the Washington Administrative Code.  The Council regularly reviews updated editions of each model code and standards every three years. 
 
International Wildland Urban Interface Code. 
The International Wildland Urban Interface Code (WUIC) is a model code developed and published by the International Code Council, Inc. (ICC).  The ICC is a nonprofit organization that develops and publishes model codes for building, construction, and design standards. Updates to the codes are developed and published on a three-year cycle. 
 
A wildland urban interface (WUI) area is defined in the WUIC as the geographical areas where structures and other human development meets or intermingles with wildland or vegetative fuels.  The WUIC establishes minimum regulations for land use and the built environment in designated WUI areas for the stated purpose of mitigating wildfire hazard.  The WUIC applies to the construction, alteration, movement, repair, maintenance, and use of any building, structure, or premises within the WUI areas of a jurisdiction.  
 
Department of Natural Resources. 
The Department of Natural Resources (DNR) has the direct charge and responsibility over all matters pertaining to forest fire services in the state.  The forest fire-related duties of the DNR include enforcing all forest fire-related laws, investigating the cause of forest fires, and directing fire suppression efforts.  In 2019, the DNR developed a wildland-urban interface map using the United States Department of Agriculture Forest Service Wildfire Hazard Potential data. 
 
Under current law, upon the completion of the statewide mapping of WUI areas, the Act must consist of the following provisions of the 2018 International WUIC as it relates to:

• Roof covering?Roofs on new constructions or replacement roof coverings on buildings must be constructed or replaced with a roof covering that can preclude entry of flames or is made of ignition-resistant materials as specified in accordance with the WUIC.
• Exterior walls?Exterior walls of buildings or structures must be constructed with methods and materials as specified in the WUIC that includes using heavy timber or log wall construction or other noncombustible or fire retardant-treated wood.
• Appendages and projections?Unenclosed accessory structures attached to buildings with habitable spaces, such as decks, must be constructed with methods and fire-resistant materials in accordance with the International WUIC.
• Driveways?Driveways must be provided where any portion of an exterior wall of the first story of the building is located more than 150 feet from a fire apparatus access road.

The Council has taken action to adopt the required and other provisions of the WUIC, which are scheduled to take effect on March 15, 2024.

Standards for Manufactured Housing. 
The Department of Labor and Industries (L&I) regulates factory assembled structures, which include manufactured and mobile homes, recreational vehicles, and factory-built housing and commercial structures.  A manufactured home is a single-family dwelling built in accordance with the United States Department of Housing and Urban Development (HUD) Manufactured Home Construction and Safety Standards Act, which is a national, preemptive building code.  A mobile home is a factory-built dwelling built before June 15, 1976, to standards other than that code, and acceptable under applicable state codes in effect at the time of construction or introduction of the home in this state.

Except for exterior structures, the WUIC does not apply to manufactured housing units approved by HUD or the L&I prior to March 15, 2024.  The Council may adopt or amend rules to exempt manufactured housing units approved by HUD or the L&I prior to March 15, 2024.  The rules may only apply to the approved manufactured housing units and may not include exterior structures such as decks, porches, balconies, stairs, fences, and other similar accessory structures.  Upon adoption of such rules, the exemption in state law expires, and the Council must provide written notice of the adoption or amendment of the rules to affected parties, the Chief Clerk of the House of Representatives, the Secretary of the Senate, the Office of the Code Reviser, and others as deemed appropriate by the Council.