This bill directs the State Building Code Council (SBCC) to adopt by rule a mandatory appendix to the Washington‑amended International Building Code establishing a performance‑based code compliance pathway for low‑rise residential buildings. It amends RCW 19.27A.020 and adds a new section to chapter 19.27 RCW. The appendix applies to buildings of one to six stories above grade plane that are not high‑rise under IBC section 202, and the bill defines “low‑rise residential building” as residential buildings with one to 24 dwelling units. The SBCC must also adopt section R406 of the International Energy Conservation Code as part of the appendix. The SBCC must convene a technical advisory group including subject matter experts and at least the Department of Labor and Industries, Department of Commerce, University of Washington, and Washington State University to recommend performance‑based code amendments. The group must develop performance criteria categories and targets for building systems, components, products, and materials, consider existing and emerging nationally recognized standards and certification frameworks (including work by the National Institute of Building Sciences), and ensure the new pathway supports integrated compliance across the IBC, the Washington state energy codes, and rules addressing building‑related greenhouse gas emissions. The SBCC must adopt rules to recognize housing system and plan certifications issued by independent, nationally recognized third‑party evaluators; recognized certifications are deemed to demonstrate compliance and must be accepted by local permitting and inspection authorities within the scope of the certification. Advisory group recommendations must be provided in time for SBCC action in the first substantive state building code update after January 1, 2027, and SBCC must consult with the Department of Enterprise Services as required by law. Legally, this is a procedural and regulatory change that creates a new, performance‑based compliance pathway through rulemaking and recognition of third‑party certifications; it modifies existing statute and adds a new statutory section. The extracted text does not create or change criminal offenses or penalties. Important details are missing from the extract: the full text of the mandatory appendix and the specific performance criteria; how SBCC will define or qualify “independent, nationally recognized” third‑party organizations; the exact relationship between the “one to six stories” scope and the “one to 24 dwelling units” definition; the content of IECC section R406; and detailed procedures for harmonizing compliance with energy and greenhouse gas rules.

If enacted, the bill will create a new, mandatory performance-based compliance route for most low-rise residential buildings that lets builders show they meet safety, energy, and greenhouse gas targets through measurable outcomes (for example engineering analysis, testing, modeling, or recognized third‑party certifications) instead of only following prescriptive materials or assembly rules. The State Building Code Council must write the rules, adopt section R406 of the energy code, and accept certain nationally recognized third‑party housing system or plan certifications as proof of compliance that local permit authorities must take as meeting code within the certification’s scope. The people and organizations most affected will be builders and developers, who will likely gain more options to use innovative systems or certified products and potentially shorten permitting timelines; independent national certification bodies, which could see increased demand if they meet the council’s recognition criteria; local permitting authorities, which must accept recognized certifications and will need to adjust review and inspection practices; and the SBCC and participating state agencies and universities, which will bear the work and costs of convening a technical advisory group and writing the new rules. Important details are missing from the facts provided — notably the specific performance targets, how certifiers will be qualified, the exact scope between "one to six stories" and "one to 24 units," and the contents of R406 — so the practical outcomes will depend on those yet‑to‑be‑written rules and the timing tied to the first substantive code update after January 1, 2027.