When did WA ADU rules change?
✓ Verified against code · August 19, 2026
HB 1337 passed in 2023 and set June 30, 2025 as the compliance deadline for larger Washington cities. But the actual timeline on the ground was scattered: Edmonds complied a full year early (June 2024) and Sammamish six months early (January 2025), while Bellevue and Everett didn't finish their rewrites until July 2025, and Olympia didn't adopt its package until November 2025 — about five months after the deadline. Several cities have already amended their post-HB-1337 code again, including Seattle's January 2026 rewrite and Redmond's pending Ordinance 3261. There's no single date; check your city's effective date before relying on any rule.
Citation: HB 1337
How current is this?
Washington’s ADU rules run under HB 1337 (2023). HB 1337 required every Washington city over 25,000 people to allow two ADUs per residential lot, drop owner-occupancy requirements, cap size limits no lower than 1,000 sq ft, cap height limits no lower than 24 ft, and stop requiring parking near major transit — with compliance due June 30, 2025 for larger cities. We verified this answer against primary sources on August 19, 2026, and every change we catch is logged in the changelog.
More Washington ADU questions
- How many ADUs can I build in Washington?
- What is HB 1337?
- Do I need parking for an ADU in Washington?
- Can cities require me to live on the property?
- How big can an ADU be in Washington?
- Can I sell an ADU separately in Washington?
- Which WA cities have pre-approved ADU plans?
- How tall can an ADU be in Washington?
- How close to my property line can an ADU be built?
- Will I have to pay impact fees on an ADU in Washington?
- How long does it take to get an ADU permit in Washington?
Not legal advice — local ordinances can go further than the state floor. The citation above points at the governing statute; check your city’s code for the specifics.