The bill establishes a self-certification program for accessory dwelling unit (ADU) project permit applications in cities that plan under chapter 36.70A RCW. It allows registered architects to self-certify compliance with building code requirements for the construction of detached ADUs. The bill mandates that cities adopt specific rules for the self-certification program, including professional requirements for architects, random audits of self-certified applications, penalties for failed audits, and insurance coverage requirements. Additionally, cities must create a self-certification form that includes various attestations and agreements from the architect and property owner.

Furthermore, the bill requires cities operating a self-certification program to notify the relevant department of any penalties imposed on architects due to failed audits and to maintain a database of architects subject to such penalties. Cities must also submit a report on their self-certification program by July 31, 2028, detailing project statistics and audit results, while the department will compile and report this information to the legislature by December 31, 2028. The bill clarifies that it does not affect the validity of any existing self-certification programs prior to its effective date.