AN ACT Relating to residential housing regulations; adding new sections to chapter 19.27 RCW; adding new sections to chapter 36.70A RCW; and creating a new section.

(1) The legislature finds that lowering the cost of middle and multiplex housing construction will increase the housing supply and help address the state's shortage of affordable housing. It further finds that home builders and residentially focused architects are more familiar with the provisions of the international residential code. Allowing middle and multiplex housing to be built according to the standards of the international residential code will result in housing being easier to build and more affordable without sacrificing quality and safety. Therefore, the legislature intends to simplify the production of middle and multiplex housing by allowing more types of housing to use provisions of the international residential code.

(2) The state building code council shall convene a technical advisory group for the purpose of recommending the additions or amendments to rules or codes that are necessary for the council to apply the Washington state residential code to multiplex housing. The technical advisory group shall determine the most efficient mechanism to implement these changes in the Washington state residential code. These recommendations must include those code changes necessary to ensure public health and safety in multifamily housing under the international residential code and must consider the life safety systems and accessibility requirements for multiplex housing from the Washington state building code.

(3) The advisory group shall provide its recommendations to the council in time for the council to adopt or amend rules or codes as necessary for implementation in the 2024 international building code. The council shall take action to adopt additions and amendments to rules or codes as necessary to apply the international residential code to multiplex housing by November 1, 2026.

(4) For the purposes of this section, "multiplex housing" means a building with up to six dwelling units consolidated into a single structure with common walls and floors and a functional primary street entrance, or a building of up to three stories containing up to six dwelling units consolidated into a single structure.

(1) The state building code council shall convene a technical advisory group for the purpose of recommending amendments to the international building code that would allow for a minimum dwelling unit size that is less than the requirements for an efficiency dwelling unit in the international building code. The technical advisory group shall consider aligning the state building code sections related to interior environment with the relevant sections of the national healthy housing standard published by the national center for healthy housing. When developing the recommendations, the technical advisory group must review the differences between the state building code and the national healthy housing standard and allow experts in public health and fire safety to comment during the process.

(2) The technical advisory group shall provide its recommendations to the council in time for the council to adopt or amend rules or codes as necessary for implementation in the 2024 international building code. The council shall take action to adopt additions and amendments to rules or codes as necessary by November 1, 2026.

NEW SECTION. Sec. 3. The office of regulatory innovation and assistance shall contract with a qualified external consultant or entity to develop a standard energy code plan set demonstrating a prescriptive compliance pathway that will meet or exceed all energy code regulations for residential housing in the state subject to the international residential code. The standard energy code plan set may be used, but is not required, by local governments and building industries. In developing the standard energy code plan set, the consultant shall, at a minimum, seek feedback from cities, counties, building industries, and building officials. The standard energy code plan set must be completed by June 30, 2025.

(1) For retrofits of existing buildings to be used for residential housing, a city or county must allow the portion of exterior wall assemblies that include insulation to project up to an additional eight inches into the setbacks on all sides.

(2) For existing nonconforming buildings already projecting into setbacks, a city or county must allow the portion of exterior wall assemblies that include insulation to project up to an additional eight inches into the setbacks on all sides if the building is to be used for residential housing.

(3) For retrofits of existing buildings to be used for residential housing, gross floor area must be measured from the interior face of the exterior walls, which includes drywall, as typically depicted on the architectural floor plans.

(4) Nothing in this section prohibits a city or county from applying the requirements of the state building code or requires a city or county to allow a setback of less than 36 inches between residential dwelling units.

(5)(a) The requirements in this section apply to any county planning under this chapter, and any cities within those counties with a population greater than 6,000.

(b) A city or county subject to the requirements of this section must adopt or amend by ordinance, and incorporate into their development regulations, zoning regulations, and other official controls the requirements of this section, to take effect six months after the jurisdiction's next periodic comprehensive plan update required under RCW 36.70A.130.

(c) In any city or county subject to the requirements of this section that has not adopted or amended ordinances, regulations, or other official controls as required under this section, the requirements of this section supersede, preempt, and invalidate any conflicting local development regulations.

(a) Any required setback must be measured to the outside face of the foundation, and a city or county must allow the portion of exterior wall assemblies that include insulation to project up to eight inches into setbacks on all sides; and

(b) If gross floor area is measured from the exterior face of the exterior walls, a city or county must allow the residential housing to exceed any gross floor limitations by an additional eight inches on each exterior wall to accommodate additional insulation.

(2) For new construction and the retrofit of existing buildings meeting passive house requirements, a city or county must allow residential housing to exceed the maximum allowable roof height by eight inches to accommodate additional insulation.

(3) For the purposes of this section, "passive house requirements" means the criteria for certification as a passive house by phius or the international passive house institute.

(5)(a) The requirements in this section apply to any county planning under this chapter, and any cities within those counties with a population greater than 6,000.

Any county planning under this chapter, and any cities within those counties with a population greater than 6,000, may not require off-street parking as a condition of permitting a residential project if compliance with tree retention or protection requirements would otherwise make a proposed residential development or redevelopment infeasible.