Straight-ahead summaries built from the official bill text. We keep the source links front and center and leave the decision up to you.
HB1345 • 2026
Establishing limitations on detached accessory dwelling units outside of urban growth areas.
This bill passed both chambers and reached final enrollment, even if later executive action is not shown here.
Using official source text because the generated explanation was unavailable or could not be confirmed against the official bill text.
Detached ADU limits
These notes stay tied to the official amendment files and metadata from the legislature.
1478 • Peterson
Plain English: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 1345 AMH PETE VASE 222 1 - Official Print By Representative Peterson 1345 AMH PETE VASE 222 HB 1345 - H AMD 1478 ADOPTED 01/22/2026 On page 2, line 23, after "parcel;" strike "and" On page 2, line 24, after "(j)" insert "The detached accessory dwelling unit must not be allowed on nonconforming lots under one acre; and (k)" On page 3, line 20, after "period" strike "within the overall underlying density" and insert "so that the housing units will not exceed the underlying densities for the comprehensive plan designations and zones" On page 3, line 21, after "areas;" strike "and" On page 3, beginning on line 23, after "plan" strike all material through "areas" on line 25 and insert "under (b) of this subsection" On page 3, line 26, after "years" insert "; and (d) The county must include the following limits on population growth targets in its comprehensive plan: (i) If the county is a rural county as defined in RCW 43.160.020, the county may allocate no more than 10 percent of its rural population target to detached accessory dwelling units; and (ii) If the county is not a rural county as defined in RCW 43.160.020, the county may allocate no more than seven percent of its rural population target to detached accessory dwelling units" 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 1345 AMH PETE VASE 222 2 - Official Print EFFECT: Makes the following changes to the underlying bill: Specifies that fully planning counties under the Growth Management Act that choose to allow detached accessory dwelling units (DADUs) outside of urban growth areas (UGAs) must prohibit these DADUs from being allowed on nonconforming lots under one acre.
618 • Peterson
Plain English: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 1345 AMH PETE VASE 170 1 - Official Print EFFECT: Specifies that fully planning counties under the Growth Management Act that choose to allow detached accessory dwelling units (DADUs) outside of urban growth areas must prohibit these DADUs from being allowed on nonconforming lots under one acre.
748 • Short
Plain English: 1345.E AMS SHOR S5611.1 EHB 1345 - S AMD 748 By Senator Short NOT ADOPTED 03/03/2026 On page 2, line 4, after "metered" insert ", except in a county 1 classified as a frontier county under RCW 43.160.020"2 On page 2, line 28, after " (2)" strike "In" and insert " (a) 3 Except as provided under (b) of this subsection (2), in"4 On page 2, at the beginning of line 32, strike " (a)" and insert 5 "(i)" 6 On page 2, at the beginning of line 37, strike " (b)" and insert 7 "(ii)" 8 On page 3, at the beginning of line 5, strike " (c)" and insert 9 "(iii)" 10 Correct any internal references accordingly.
762 • Wagoner
Plain English: 1345.E AMS WAGO S5690.1 EHB 1345 - S AMD 762 By Senator Wagoner WITHDRAWN 03/03/2026 On page 2, line 4, after "metered" insert ", except in rural 1 county as defined in RCW 82.14.370" 2 On page 2, line 28, after " (2)" strike "In" and insert " (a) 3 Except as provided under (b) of this subsection (2), in"4 On page 2, at the beginning of line 32, strike " (a)" and insert 5 "(i)" 6 On page 2, at the beginning of line 37, strike " (b)" and insert 7 "(ii)" 8 On page 3, at the beginning of line 5, strike " (c)" and insert 9 "(iii)" 10 Correct any internal references accordingly.
839 • Schoesler
Plain English: 1345.E AMS SCHO S5913.1 EHB 1345 - S AMD 839 By Senator Schoesler NOT ADOPTED 03/03/2026 On page 2, beginning on line 3, strike all of subsection (d)1 Reletter the remaining subsections consecutively and correct any 2 internal references accordingly.
Effective date 6/11/2026.
Detached ADU limits
AN ACT Relating to establishing limitations on detached accessory 1 dwelling units outside of urban growth areas; amending RCW 2 36.70A.696; and adding a new section to chapter 36.70A RCW.3 BE IT ENACTED BY THE LEGISLATURE OF THE STATE OF WASHINGTON:4 NEW SECTION. Sec. 1. A new section is added to chapter 36.70A 5 RCW to read as follows: 6 (1) Counties that are required or choose to plan under this 7 chapter may allow detached accessory dwelling units outside of urban 8 growth areas if the county meets the requirements in subsections (2) 9 and (3) of this section, and such detached accessory dwelling units 10 are subject to development regulations that include the following 11 limitations: 12 (a) No parcel may have more than one accessory dwelling unit, 13 whether attached or detached; 14 (b) The detached accessory dwelling unit must be subject to the 15 water supply requirements of RCW 19.27.097 and any groundwater 16 mitigation requirements adopted by the county or department of 17 ecology; 18 (c) The combined water withdrawal for the detached accessory 19 dwelling unit, the principal unit, and any other domestic uses on the 20 H-0508.2 HOUSE BILL 1345 State of Washington 69th Legislature 2025 Regular Session By Representatives Low, Peterson, Tharinger, Nance, and Gregerson Read first time 01/16/25. Referred to Committee on Housing. p. 1 HB 1345 parcel may not exceed the use limitations in RCW 90.44.050 for 1 domestic use; 2 (d) Withdrawals of water by each dwelling unit on the parcel must 3 be metered; 4 (e) The applicant must provide documentation that the existing or 5 proposed sewage or septic system is capable of handling the 6 additional demand placed upon it by the detached accessory dwelling 7 unit; 8 (f) The gross floor area of the detached accessory dwelling unit 9 may not exceed the gross floor area of what could be authorized by 10 the county as an expansion of the principal unit to create an 11 attached accessory dwelling unit; however, in no case may the gross 12 floor area be greater than 1,296 square feet. Floor areas exclude 13 garages, porches, and unfinished basements; 14 (g) The detached accessory dwelling unit must utilize the same 15 driveway or other means of ingress and egress as the principal unit;16 (h) The detached accessory dwelling unit must be sited within 150 17 feet of the principal unit; 18 (i) The detached accessory dwelling unit may be the existing 19 principal unit if the existing principal unit meets the requirements 20 of this subsection, is a single-family dwelling unit, and a new 21 principal unit that is a single-family dwelling unit is constructed 22 on the same parcel; and 23 (j) A parcel may not be subdivided for the purposes of avoiding 24 the limits on development regulations described in this subsection.25 (2) In addition to the requirements in subsections (1) and (3) of 26 this section, counties that allow detached accessory dwelling units 27 outside of urban growth areas must have the following code 28 enforcement measures in place: 29 (a) A voluntary county code compliance process through which the 30 owner of an unpermitted detached accessory dwelling unit may bring 31 the unpermitted detached accessory dwelling unit into compliance with 32 applicable regulations. In such a case, a permit penalty of at least 33 double the normal permit fee must be applied; 34 (b) Owners who do not seek voluntary compliance and are found to 35 have constructed or placed a detached accessory dwelling unit without 36 all required permits must be subject to a civil infraction of at 37 least $1,000 and must be required to remove the detached accessory 38 dwelling unit or ensure that it meets all existing development 39 regulations, if applicable. A penalty of at least triple the normal 40 p. 2 HB 1345 permit fee must be applied if the accessory dwelling unit remains and 1 meets all existing development regulations; and 2 (c) Any owner who does not seek voluntary compliance and has 3 received a civil infraction for constructing or placing an accessory 4 dwelling unit without all required permits must be prohibited from 5 receiving any permits for the placement or construction of new 6 accessory dwelling units for a period of at least three years.7 (3) In addition to the requirements in subsections (1) and (2) of 8 this section, counties that allow detached accessory dwelling units 9 outside of urban growth areas must take the following actions to 10 account for detached accessory dwelling unit development:11 (a) The county must track and annually report to the department 12 the number of detached accessory dwelling unit permits completed;13 (b) Utilizing the data collected and reported in (a) of this 14 subsection, the county must update its comprehensive land use plan 15 during its next required review and all subsequent reviews required 16 under RCW 36.70A.130(5) to properly account for the number of 17 detached accessory dwelling units completed since the effective date 18 of this section and the projected development over the next 20-year 19 planning period within the overall underlying density outside of 20 urban growth areas; and 21 (c) The county must limit future amendments to its comprehensive 22 land use plan accounting for actual and projected detached accessory 23 dwelling units within the overall underlying density outside of urban 24 growth areas such that these amendments may not occur more than once 25 every five years. 26 (4) Subsection (1) of this section is in addition to other county 27 authority enumerated in this chapter and does not:28 (a) Affect or modify the validity of any county ordinance 29 authorizing accessory dwelling units adopted prior to the effective 30 date of this section; 31 (b) Exclude other means of authorizing accessory dwelling units 32 in urban or rural areas, if consistent with this section; or33 (c) Exclude other innovative techniques under RCW 34 36.70A.070(5)(b), 36.70A.090, or 36.70A.177, if consistent with this 35 section. 36 Sec. 2. RCW 36.70A.696 and 2023 c 334 s 2 are each amended to 37 read as follows: 38 p. 3 HB 1345 The definitions in this section apply throughout RCW 36.70A.697, 1 36.70A.698, 36.70A.680, ((and)) 36.70A.681, and section 1 of this act 2 unless the context clearly requires otherwise. 3 (1) "Accessory dwelling unit" means a dwelling unit located on 4 the same lot as a single-family housing unit, duplex, triplex, 5 townhome, or other housing unit. 6 (2) "Attached accessory dwelling unit" means an accessory 7 dwelling unit located within or attached to a single-family housing 8 unit, duplex, triplex, townhome, or other housing unit.9 (3) "City" means any city, code city, and town located in a 10 county planning under RCW 36.70A.040. 11 (4) "County" means any county planning under RCW 36.70A.040.12 (5) "Detached accessory dwelling unit" means an accessory 13 dwelling unit that consists partly or entirely of a building that is 14 separate and detached from a single-family housing unit, duplex, 15 triplex, townhome, or other housing unit and is on the same property.16 (6) "Dwelling unit" means a residential living unit that provides 17 complete independent living facilities for one or more persons and 18 that includes permanent provisions for living, sleeping, eating, 19 cooking, and sanitation. 20 (7) "Gross floor area" means the interior habitable area of a 21 dwelling unit including basements and attics but not including a 22 garage or accessory structure. 23 (8) "Major transit stop" means: 24 (a) A stop on a high capacity transportation system funded or 25 expanded under the provisions of chapter 81.104 RCW;26 (b) Commuter rail stops; 27 (c) Stops on rail or fixed guideway systems, including 28 transitways; 29 (d) Stops on bus rapid transit routes or routes that run on high 30 occupancy vehicle lanes; or 31 (e) Stops for a bus or other transit mode providing actual fixed 32 route service at intervals of at least fifteen minutes for at least 33 five hours during the peak hours of operation on weekdays.34 (9) "Owner" means any person who has at least 50 percent 35 ownership in a property on which an accessory dwelling unit is 36 located. 37 (10) "Principal unit" means the single-family housing unit, 38 duplex, triplex, townhome, or other housing unit located on the same 39 lot as an accessory dwelling unit. 40 p. 4 HB 1345 (11) "Short-term rental" means a lodging use, that is not a hotel 1 or motel or bed and breakfast, in which a dwelling unit, or portion 2 thereof, is offered or provided to a guest by a short-term rental 3 operator for a fee for fewer than 30 consecutive nights.4 --- END --- p. 5 HB 1345