This bill (House Bill 1010) creates a new section in chapter 36.70A RCW that authorizes counties to allow one detached accessory dwelling unit (DADU) per parcel in rural areas even when such units would otherwise be prohibited by county comprehensive plans or planning policies, provided specified development regulations are met. Those requirements include limits of one ADU per parcel, a maximum gross floor area of 1,296 square feet (or the lesser area that could be authorized as an attached ADU), water supply and metering tied to the primary dwelling and not from sources closed to appropriation (with reference to RCW 19.27.097), prohibition on encroachment into critical area buffers, documentation and licensed inspection of sewage/septic systems before building permit issuance if the DADU connects to an existing system, use of the same driveway, exterior appearance approximating the primary dwelling (with an exception for mobile/manufactured homes), protections to avoid conversion of agricultural or forestlands, and a prohibition on subdividing parcels to evade these limits. Counties that authorize DADUs must amend their comprehensive plans or planning policies at the next regularly scheduled update to allow such DADUs consistent with the new section, and population growth from qualifying DADUs may not be counted toward rural or urban growth targets. The bill also amends existing growth management statutes (including RCW 36.70A.177, RCW 36.70A.130, and RCW 36.70A.210 as shown) to clarify and limit how counties regulate agricultural lands and to adjust periodic review, reporting, and countywide/multicounty planning policy processes. It requires department review and notification of city eligibility for partial reviews, sets deadlines and procedures for periodic reviews and revisions of comprehensive plans and regulations (with detailed schedules by county), requires implementation progress reports for certain larger counties and cities five years after plan reviews, and provides conditions under which counties need not revise regulations protecting critical areas for agricultural activities in participating watersheds. It also requires countywide and multicounty planning policies that authorize DADUs to be amended at their next regularly scheduled updates and reiterates that population growth from qualifying DADUs is not to be counted for growth-target determinations. These provisions constitute a mix of new law (the new DADU authorization section), amendments to existing law (multiple RCWs governing growth management and countywide/multicounty planning policies), and procedural changes (new review, reporting, and amendment obligations and timelines). The text provided is incomplete in places: the full opt-out criteria and related provisions for small cities/towns in the RCW 36.70A.130 amendment are not included, the identity of “the department” referenced for reviews and guidelines is not specified, the amendment text for RCW 36.70A.210 is only partly shown, and no effective dates, enforcement details, or penalty provisions are present in the extracted material.

If enacted, counties would be able to let homeowners build one detached accessory dwelling unit (DADU) on rural parcels regardless of current local planning bans, so long as the unit meets specific limits and technical conditions: it must be the only ADU on the parcel, be no larger than about 1,296 square feet (or smaller if local expansion limits are lower), share the primary driveway, generally match the main house’s exterior, avoid critical-area buffers and agricultural or forestland, use water tied to the main dwelling’s water right (not from closed sources), have metered water withdrawals for each unit, and demonstrate that septic or on-site systems can handle the added demand (with inspections by a licensed contractor if tied to an existing system). This likely increases housing options in rural areas and gives property owners a clearer path to add rental or multigenerational housing, while shifting measurable growth off of official rural/urban growth target calculations when DADUs meet the rules. The parties most affected are counties (they gain a new option to expand rural housing but must amend comprehensive, countywide, or multicounty plans at their next scheduled update and may face extra planning and enforcement workload), building permit authorities and licensed septic contractors (more inspections and permit checks, and likely modest fee or staffing impacts), property owners (new development opportunity but with likely costs for septic upgrades, inspections, water metering, and meeting siting/design constraints), and agricultural/forestland interests (siting rules are intended to protect conversion risks). The bill text provided omits some implementation details—effective dates, full opt-out criteria for small cities, the identity of “the department” handling certain reviews, and some amendment language—so exact timing, enforcement, and funding or grant eligibility remain unclear.