BySenate Local Government, Land Use & Tribal Affairs (originally sponsored by Senators Braun, Cleveland, Conway, Gildon, Liias, Lovelett, Mullet, Wellman, and J. Wilson)

AN ACT Relating to establishing limitations on detached accessory dwelling units outside 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 may allow detached accessory dwelling units outside of urban growth areas if such detached accessory dwelling units are subject to development regulations that include the following limitations:

(a) No parcel may have more than one attached or detached accessory dwelling unit.

(b) The detached accessory dwelling unit is subject to the water supply requirements of RCW 19.27.097.

(c) 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.

(d) The floor area of the detached accessory dwelling unit may not exceed the floor area of what could be authorized by the county as an expansion of the primary dwelling to create an attached accessory dwelling unit, and may not be greater than 1,296 square feet. Floor areas are exclusive of garages, porches, and unfinished basements.

(e) The detached accessory dwelling unit must be located within the same acre as the primary dwelling unit and must utilize the same driveway as the primary dwelling. An existing driveway may not be extended or altered to service the detached accessory dwelling unit.

(f) The detached accessory dwelling unit must be sited to prevent loss of land that is defined as "agricultural land" or "forestland" under this chapter.

(g) A parcel may not be subdivided for the purposes of avoiding the limits on development regulations described in this subsection.

(h) The detached accessory dwelling unit must be located on a conforming lot that does not contain a critical area or areas as defined under this chapter.

(i) If the detached accessory dwelling unit is offered as a short-term rental as defined in RCW 36.70A.696, the primary unit must be owner occupied.

(2) A county must deny an application for a detached accessory dwelling unit if the primary dwelling unit was built after the effective date of this section.

(3) In addition to the authority provided in subsection (1) of this section, counties may allow detached accessory dwelling units by adopting development regulations that are substantially similar to those in effect as of January 1, 2024, in a county with a population exceeding 2,000,000.

(4) Subsection (1) of this section is cumulative to other county authority enumerated in this chapter and does not:

(a) Affect or modify the validity of any county ordinance authorizing accessory dwelling units adopted prior to the effective date of this section;

(b) Exclude other means of authorizing accessory dwelling units in urban or rural areas, if consistent with this act; or

(c) Exclude other innovative techniques under RCW 36.70A.070(5)(b), 36.70A.090, or 36.70A.177, if consistent with this act.

Sec. 2. RCW 36.70A.696 and 2023 c 334 s 2 are each amended to read as follows:

The definitions in this section apply throughout RCW 36.70A.697, 36.70A.698, 36.70A.680, ((and)) 36.70A.681, and section 1 of this act unless the context clearly requires otherwise.

(1) "Accessory dwelling unit" means a dwelling unit located on the same lot as a single-family housing unit, duplex, triplex, townhome, or other housing unit.

(2) "Attached accessory dwelling unit" means an accessory dwelling unit located within or attached to a single-family housing unit, duplex, triplex, townhome, or other housing unit.

(3) "City" means any city, code city, and town located in a county planning under RCW 36.70A.040.

(5) "Detached accessory dwelling unit" means an accessory dwelling unit that consists partly or entirely of a building that is separate and detached from a single-family housing unit, duplex, triplex, townhome, or other housing unit and is on the same property.

(6) "Dwelling unit" means a residential living unit that provides complete independent living facilities for one or more persons and that includes permanent provisions for living, sleeping, eating, cooking, and sanitation.

(7) "Gross floor area" means the interior habitable area of a dwelling unit including basements and attics but not including a garage or accessory structure.

(a) A stop on a high capacity transportation system funded or expanded under the provisions of chapter 81.104 RCW;

(d) Stops on bus rapid transit routes or routes that run on high occupancy vehicle lanes; or

(e) Stops for a bus or other transit mode providing actual fixed route service at intervals of at least fifteen minutes for at least five hours during the peak hours of operation on weekdays.

(9) "Owner" means any person who has at least 50 percent ownership in a property on which an accessory dwelling unit is located.

(10) "Principal unit" means the single-family housing unit, duplex, triplex, townhome, or other housing unit located on the same lot as an accessory dwelling unit.

(11) "Short-term rental" means a lodging use, that is not a hotel or motel or bed and breakfast, in which a dwelling unit, or portion thereof, is offered or provided to a guest by a short-term rental operator for a fee for fewer than 30 consecutive nights.