Growth Management Act.  The Growth Management Act (GMA) is the comprehensive land use planning framework for counties and cities in Washington.  The GMA establishes land use designation and environmental protection requirements for all Washington counties and cities.  The GMA also establishes a significantly wider array of planning duties for 28 counties, and the cities within those counties, that are obligated to satisfy all planning requirements of the GMA.

The GMA directs fully planning jurisdictions to adopt internally consistent comprehensive land use plans. Comprehensive plans are implemented through locally adopted development regulations, and both the plans and the local regulations are subject to review and revision requirements prescribed in the GMA.

State Building Code.  Before developing land, a developer must obtain various permits from the local government with jurisdiction over the land allowing the development, including a building permit.  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 (IBC), the International Residential Code (IRC), and the Energy Code.

The State Building Code Council (Council) is responsible for adopting, amending, and maintaining 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 reviews updated editions of each model code and standard every three years.

Local governments may also adopt local amendments to the Code, though the amendments cannot diminish the minimum performance standards required by the Code, and local governments cannot increase energy efficiency requirements for residences beyond what is required in the Code.

Accessory Dwelling Units.  Under the GMA, an ADU is defined as a dwelling unit that is located on the same lot as a single-family housing unit, duplex, triplex, townhome, or other housing unit, which is referred to as the principal unit. A dwelling unit means a residential living unit that provides complete independent living facilities for one or more persons and permanent provisions for living, sleeping, eating, cooking, and sanitation.

An attached accessory dwelling unit is defined as an ADU located within or attached to the principal unit, and a detached accessory dwelling unit is defined as an ADU that consists partly or entirely of a building that is separate and detached from the principal unit and is on the same property.

Registered Architects.  In order to practice architecture in Washington, an architect must be registered in the state.  In order to qualify for registration, an architect must meet education or work experience and training requirements, and must pass an examination.  Registrations are renewed every two years, upon the completion of professional development requirements and the payment of a fee.

Cities planning under the GMA may operate self-certification programs for the construction or development of detached ADUs on residential properties.  If a permit application has been self-certified as required by the program, then, after determining that the application is complete, the city may consider the application to be in compliance with applicable Code requirements, as well as with local building, electric, plumbing, mechanical, and fire code requirements.  Only registered architects may participate in a self-certification program.  A permit issued pursuant to a self-certification program has the same effect as a permit issued after a full project review.

Each city must adopt rules for its self-certification program.  The rules must include, at a minimum:

• any requirements other than registration for an architect to qualify for the program;
• requirements for random audits of self-certified program applications in order to verify that applications are compliant with applicable building code requirements, including that at least 20 percent of applications, or five applications, whichever is fewer, must be audited each year, in addition to any nonrandom audits the city deems necessary;
• any penalties for failing an audit, including that an architect who certifies an application that subsequently fails an audit must be temporarily prohibited from participating in the self-certification program for at least one year, and that an architect who fails two audits within a five-year period must be barred from participating in the program; and
• requirements for architects participating in the program to maintain appropriate levels of professional liability insurance.

Each city may, at its discretion, adopt additional rules or exceed the minimum required rules for its program.

Each city must create a standardized self-certification program form as part of its program.  The form must include:

•  an attestation that the certifying architect will correct any false or inaccurate statements in the application as soon as the architect learns of them;
• an acknowledgement from the architect that participation in the program is conditioned upon accuracy in the certification, and that the discovery of inaccuracies or errors may result in being suspended or removed from the program;
• an agreement signed by the architect, the property owner, and the owner or a representative of the company that will construct the ADU that releases the city from any liability for claims or injuries connected with the design, construction, or issuance of a project permit for the ADU; and
• an acknowledgment from the property owner that it will be the owner's responsibility to correct any nonconformities with applicable building code requirements within a reasonable time after they are discovered.

Cities operating self-certification programs must report any penalties imposed for failed audits to the Department of Commerce (Commerce), and Commerce must maintain a database available to cities of architects that are currently subject to penalties.  Cities may not accept a self-certified application from an architect who is subject to penalties because of a failed audit in another city.  Commerce must provide for administrative hearing procedures to resolve any disputes over audit results and penalties.

A city operating a self-certification program must submit a report on its program to Commerce by July 31, 2028.  The report must include the number of self-certification applications received, the number of permits issued through the self-certification program, the average length of time that it took for a project permit to be issued on a detached ADU application for self-certified permit applications and nonself-certified permit applications, and the results of the city's audits of self-certified project permit applications.  Commerce must summarize the information that it receives from cities in a report to the Legislature by December 31, 2028.

Self-certification and similar programs operated by local governments prior to July 26, 2025, may continue to operate outside of the requirements otherwise applicable to self-certification programs.