Washington State Building Code.?
The Washington 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, including the International Building Code (IBC), the International Residential Code (IRC), and the State Energy Code (Energy Code).

The IBC establishes minimum requirements for all buildings except detached one- and two-family dwellings and townhouses up to three stories. ?The IRC comprises all building, plumbing, mechanical, fuel gas, and electrical requirements for one- and two-family dwellings and townhouses up to three stories. ?The Energy Code establishes minimum energy efficiency requirements for all residential and nonresidential buildings.

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The State Building Code Council (SBCC) is responsible for adopting, amending, and maintaining the model codes and standards. ?Amendments to the model codes and standards adopted by the SBCC are codified in the Washington Administrative Code. ?The SBCC reviews updated editions of each model code and standard every three years.

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Efficiency Dwelling Units.?
Efficiency dwelling units, as defined by the IBC, are units that have a minimum of 190 square feet of habitable space with at least one room greater than 120 square feet. ?Sleeping units or other habitable rooms of the unit must be greater than 70 square feet. ?Each efficiency dwelling unit must be provided with:

• a separate closet;
• a bathroom with a water closet, lavatory, and bathtub or shower; and
• a kitchen sink, cooking appliance and refrigerator, and each must have a clear working space greater than 30 inches.
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National Healthy Housing Standard.
The National Healthy Housing Standard (Standard) is published by the National Center for Healthy Housing and the American Public Health Association. ?The Standard recommends minimum performance requirements for housing including:? duties of owners and occupants; structure, facilities, plumbing, and space requirements; safety and personal security; lighting and electrical systems; thermal comfort, ventilation, and energy efficiency; moisture control, solid waste, and pest management; and chemical and radiological agents. ?The Standard recommends that each dwelling unit provide privacy and adequate space for sleeping and living and that every habitable room have a minimum floor area of 70 square feet.

The SBCC must convene two technical advisory groups (TAGs) to recommend changes to the Code.? The first TAG must recommend additions or amendments to rules or codes that are necessary to apply the Washington State Residential Code to multiplex housing. ?The recommendations must include those code changes necessary to ensure public health and safety in multifamily housing under the IRC and must consider life safety systems and accessibility requirements for multiplex housing in the Code.

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The second TAG must recommend amendments to the IBC that would allow for a minimum dwelling unit size that is less than the requirements for efficiency dwelling units in the IBC. ?The TAG must consider aligning the Code sections related to interior environment with the relevant sections of the Standard. ?When developing the recommendations, the TAG must review the differences between the Code and the Standard and allow experts in public health and fire safety to comment during the process.

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Both TAGs must provide their recommendations to the SBCC in time for the SBCC to adopt or amend rules or codes as necessary for implementation in the 2024 IBC.? The SBCC must take action to adopt additions and amendments to rules or codes as necessary by November 1, 2026.

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The Office of Regulatory Innovation and Assistance must 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 subject to the IRC. ?The standard plan set may be used by local governments and building industries. ?In developing the standard plan set, the consultant must seek feedback from cities, counties, building industries, and building officials. ?The standard plan set must be completed by June 30, 2025.