Detached ADU Limitations Outside Urban Growth Areas

State Bills: Washington

Published January 22nd, 2026

Detected April 1st, 2026

Summary

The Washington State Legislature passed HB 1345, establishing new limitations on detached accessory dwelling units (ADUs) located outside urban growth areas. The bill was sponsored by Representatives Low, Peterson, Tharinger, Nance, and Gregerson and passed the House 86-5 before receiving Senate committee approval. Local governments and property developers should review existing development standards to ensure compliance with the new ADU restrictions.

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What changed

HB 1345 establishes specific limitations on detached accessory dwelling units located outside urban growth areas in Washington State. The bill passed both chambers and received the designation C 231 L 26, indicating it has been enacted into law. The legislation addresses ADU development in rural areas, potentially restricting size, placement, or permitting requirements for these structures.

Local governments responsible for land use and permitting must review and potentially update their development regulations to align with the new state requirements. Construction firms and developers planning detached ADU projects in rural areas should verify compliance with the new limitations before proceeding with permits. Property owners with existing or planned detached ADUs outside urban growth areas should consult with local planning departments to understand any grandfathering provisions or required modifications.

What to do next

Review local development regulations for alignment with new ADU limitations
Update permitting procedures for detached ADUs outside urban growth areas
Consult with legal counsel regarding compliance requirements for existing ADU projects

Source document (simplified)

Home / Bills, meetings, and session / Bills / Bill summary / HB 1345

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HB 1345 - 2025-26

Establishing limitations on detached accessory dwelling units outside of urban growth areas. Sponsors: Low, Peterson, Tharinger, Nance, Gregerson

Bill status-at-a-glance

As of Tuesday, March 31, 2026 10:52 PM

Current version:

Engrossed - EHB 1345 (View 1st engrossed)

Current status:

C 231 L 26

Where is it in the process?

Bill status-at-a-glance

As of Tuesday, March 31, 2026 10:52 PM

Current version:

Engrossed - EHB 1345 (View 1st engrossed)

Current status:

C 231 L 26

Where is it in the process?

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Bill history

View all roll calls on this bill

2025 Regular Session

In the House

Jan 16 First reading, referred to Housing. (View original bill) Jan 27 Public hearing in the House Committee on Housing at 1:30 PM. (Committee materials) Feb 6 Executive action taken in the House Committee on Housing at 8:00 AM. (Committee materials) HOUS - Majority; do pass. (Majority report) Feb 10 Referred to Rules 2 Review. Mar 6 Rules Committee relieved of further consideration. Placed on second reading. Mar 19 Returned to Rules Committee for second reading.

2026 Regular Session

In the House

Jan 12 By resolution, reintroduced and retained in present status. Jan 19 Rules Committee relieved of further consideration. Placed on second reading. Jan 22 Floor amendment(s) adopted. Rules suspended. Placed on Third Reading. Third reading, passed; yeas, 86; nays, 5; absent, 0; excused, 7. (View 1st engrossed) (View this roll call)

In the Senate

Jan 26 First reading, referred to Housing. Feb 4 Public hearing in the Senate Committee on Housing at 10:30 AM. (Committee materials) Feb 18 Executive action taken in the Senate Committee on Housing at 10:30 AM. (Committee materials) HSG - Majority; do pass. (Majority report) Feb 19 Passed to Rules Committee for second reading. Feb 24 Placed on second reading by Rules Committee. Mar 3 Rules suspended. Placed on Third Reading. Third reading, passed; yeas, 33; nays, 15; absent, 0; excused, 1. (View this roll call)