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WashingtonHB 13452025-2026 Regular SessionHouseWALLET

Establishing limitations on detached accessory dwelling units outside of urban growth areas.

Sponsored By: Sam Low (Republican)

Became Law

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Bill Overview

Analyzed Economic Effects

4 provisions identified: 0 benefits, 1 costs, 3 mixed.

Penalties for unpermitted rural ADUs

Beginning June 11, 2026, if your county allows detached ADUs outside growth areas, it must enforce against unpermitted units. If you choose voluntary compliance, the permit costs at least double the normal fee. If you do not, you face a civil infraction of at least $1,000 and must remove the unit or make it meet code. If the unit stays and meets rules, you pay at least triple the normal permit fee. If you got a civil infraction and did not seek voluntary compliance, you cannot get permits for new ADUs for at least three years.

Rural detached ADUs allowed with limits

Beginning June 11, 2026, outside urban growth areas, you can build a detached ADU only if your county allows it and you meet strict rules. Only one ADU is allowed per parcel. It must sit within 150 feet of the main home and use the same driveway. The ADU’s gross floor area cannot exceed what an attached addition could allow and is capped at 1,296 sq. ft., excluding a garage, porch, and unfinished basement. You must show a legal water supply, meter each home’s use, keep total household withdrawals within state domestic‑use limits, and meet any groundwater‑mitigation rules. You must show the septic or sewer can handle the extra load. No ADUs are allowed on nonconforming lots under one acre, and you cannot subdivide to get around these limits. An existing home may serve as the ADU if it meets these rules and a new single‑family house becomes the main home on the same parcel.

Counties track rural ADUs and cap growth

Beginning June 11, 2026, any county that allows detached ADUs outside growth areas must count and report ADU permits each year. At its next required plan review, the county must add built ADUs and 20‑year projections so rural housing does not exceed allowed densities. Plan changes under this rule can occur no more than once every five years. Rural counties may assign up to 10% of their rural population target to ADUs; non‑rural counties up to 7%.

Standard definitions for ADU terms

Beginning June 11, 2026, the law sets common definitions used in ADU rules. A detached ADU is a separate building on the same property as the main home. Gross floor area means interior living space, not a garage or accessory building. These definitions apply across the state’s ADU statutes and this section.

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Sponsors & Cosponsors

Sponsor

  • Sam Low

    Republican • House

Cosponsors

  • Greg Nance

    Democratic • House

  • Mia Gregerson

    Democratic • House

  • Steve Tharinger

    Democratic • House

  • Strom Peterson

    Democratic • House

Roll Call Votes

All Roll Calls

Yes: 119 • No: 20

Senate vote • 3/3/2026

3rd Reading & Final Passage

Yes: 33 • No: 15 • Other: 1

House vote • 1/22/2026

3rd Reading & Final Passage

Yes: 86 • No: 5 • Other: 7

Actions Timeline

  1. Effective date 6/11/2026.

    3/27/2026House

  2. Chapter 231, 2026 Laws.

    3/27/2026House

  3. Governor signed.

    3/27/2026legislature

  4. Delivered to Governor.

    3/6/2026legislature

  5. President signed.

    3/4/2026legislature

  6. Speaker signed.

    3/4/2026legislature

  7. Third reading, passed; yeas, 33; nays, 15; absent, 0; excused, 1.

    3/3/2026House

  8. Rules suspended. Placed on Third Reading.

    3/3/2026House

  9. Placed on second reading by Rules Committee.

    2/24/2026House

  10. Passed to Rules Committee for second reading.

    2/19/2026House

  11. HSG - Majority; do pass.

    2/18/2026House

  12. First reading, referred to Housing.

    1/26/2026House

  13. Third reading, passed; yeas, 86; nays, 5; absent, 0; excused, 7.

    1/22/2026House

  14. Rules suspended. Placed on Third Reading.

    1/22/2026House

  15. Floor amendment(s) adopted.

    1/22/2026House

  16. Rules Committee relieved of further consideration. Placed on second reading.

    1/19/2026House

  17. By resolution, reintroduced and retained in present status.

    1/12/2026House

  18. Returned to Rules Committee for second reading.

    3/19/2025House

  19. Rules Committee relieved of further consideration. Placed on second reading.

    3/6/2025House

  20. Referred to Rules 2 Review.

    2/10/2025House

  21. HOUS - Executive action taken by committee.

    2/6/2025House

  22. HOUS - Majority; do pass.

    2/6/2025House

  23. First reading, referred to Housing.

    1/16/2025House

Bill Text

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