Washington legislation · 2025-26 Regular Session
Washington HB1345: Detached ADU limits
Status: Signed into law, March 27, 2026
Establishing limitations on detached accessory dwelling units outside of urban growth areas.
What the bill says
An act Relating to establishing limitations on detached accessory dwelling units outside of urban growth areas; amending RCW 36.70A.696; and adding a new section to chapter 36.70A RCW. NEW SECTION.
From the enrolled text:
AN ACT Relating to establishing limitations on detached accessory dwelling units outside of urban growth areas; amending RCW 36.70A.696; and adding a new section to chapter 36.70A RCW. NEW SECTION. Sec. 1. A new section is added to chapter 36.70A RCW to read as follows: (1) Counties that are required or choose to plan under this chapter may allow detached accessory dwelling units outside of urban growth areas if the county meets the requirements in subsections (2) and (3) of this section, and such detached accessory dwelling units are subject to development regulations that include the following (b) The detached accessory dwelling unit must be subject to the water supply requirements of RCW 19.27.097 and any groundwater mitigation requirements adopted by the county or department of ecology; (c) The combined water withdrawal for the detached accessory dwelling unit, the principal unit, and any other domestic uses on the parcel may not exceed the use limitations in RCW 90.44.050 for domestic use; (d) Withdrawals of water by each dwelling unit on the parcel must be metered; (e) The applicant must provide documentation that the existing or proposed sewage or septic system is capable of handling the additional demand placed upon it by the detached accessory dwelling unit; (f) The gross floor area of the detached accessory dwelling unit may not exceed …
Sponsors
- Sam Low (R) · primary sponsor
- Strom Peterson (D)
- Steve Tharinger (D)
- Greg Nance (D)
- Mia Gregerson (D)
Latest actions
- : Effective date 6/11/2026.
- : Chapter 231, 2026 Laws.
- : Governor signed.
- : Delivered to Governor.
- : President signed.
- : Speaker signed.
- : Third reading, passed; yeas, 33; nays, 15; absent, 0; excused, 1.
- : Rules suspended. Placed on Third Reading.
- : Placed on second reading by Rules Committee.
- : Passed to Rules Committee for second reading.
Votes
- 3rd Reading & Final Passage (March 3, 2026): 33 yea, 15 nay, passed
- Senate Committee on Housing: Do pass (February 18, 2026): 7 yea, 0 nay, passed
- 3rd Reading & Final Passage (January 22, 2026): 86 yea, 5 nay, passed
- House Committee on Housing: Do pass (February 6, 2025): 17 yea, 0 nay, passed
Subjects: HOUSING AND HOMES, GROWTH MANAGEMENT
Common questions
- What is HB1345?
- HB1345 is a bill in the Washington Legislature (2025-26 Regular Session): Detached ADU limits.
- What does HB1345 do?
- In its own words: An act Relating to establishing limitations on detached accessory dwelling units outside of urban growth areas; amending RCW 36.70A.696; and adding a new section to chapter 36.70A RCW. NEW SECTION.
- What is the status of HB1345?
- Signed into law as of March 27, 2026. Latest action: Effective date 6/11/2026. (March 27, 2026).
- Who sponsored HB1345?
- Sam Low (R), with 4 co-sponsors.
- Where is the official record for HB1345?
- On the Washington Legislature website: https://app.leg.wa.gov/billsummary?BillNumber=1345&Year=2025
Source: official Washington record. Tracked by Delilah, AI for legislation across all 50 states and Congress.