ADU Guidance Update


UPDATE 5-15-23: Final draft accessory dwelling unit (ADU) requirements and policy recommendations are available for review and public comment from May 15 to June 15! This document provides detail on the requirements and local policy choices to implement HB 1337. Send your comments to Catherine McCoy,

Project Background:

Until 2021, the GMA required that any city over 20,000 population allow accessory dwelling units (ADUs). RCW 43.63A.215 required that a report and model ordinance be developed, included as Appendix A in MRSC’s “Accessory Dwelling Units: Issues and Options.”

In 2021, HB 1220 substantially increased the extent of the housing element requirements in RCW 36.70A.070(2), requiring ALL local governments planning under the GMA to consider the role of accessory dwelling units in meeting housing needs as they make adequate provisions for existing and projected needs of all economic segments of the community. 

In response to this new language, and to address the critical need to address housing supply and affordability, Commerce was updating the 1994 ADU guidance, however HB 1337, passed in the 2023 legislative session, set out more requirements for all cities and counties fully planning under the GMA. The final draft update of the 1994 guidance document incorporates the new legislation from HB 1337.

 Project Timeline:

  • 2022-2023: Stakeholder engagement conducted throughout project duration
  • Winter 2022-2023: Draft ADU recommendations for cities and counties
  • Spring 2023: Education and training materials for cities and counties to promote and implement ADU programs 
  • Summer 2023: Final ADU recommendations for cities and counties and presentations and training webinars to roll out the new guidance

For more information, please contact Catherine McCoy, Senior Planner,, work cell 360.280.3147; or Anne Fritzel, Housing Programs Manager,, work cell 360-259-2525.


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