The bill amends existing law (RCW 36.70A.536) to allow counties that are required or choose to plan under RCW 36.70A.040 to authorize middle housing types on parcels zoned for single-family residences in two places: limited areas of more intensive rural development designated under RCW 36.70A.070(5)(d)(i) and in designated urban growth areas. This is a change to land use law and county development rules that permits (but does not require) middle housing in those areas, limits units to no more than four per lot, and clarifies related development and service requirements. The bill requires that development regulations for authorized middle housing not be more restrictive than those for detached single-family residences, while allowing objective standards that apply to single-family homes (for example, setbacks, lot coverage, stormwater, clearing, tree canopy and retention). It directs that the same permit and environmental review processes used for detached single-family residences apply unless state law requires otherwise and specifies sewer and water service requirements for rural and nonrural limited areas of more intensive rural development and for urban growth areas. It references definitions in RCW 43.160.020 (rural county) and RCW 70A.115.010 (large on-site sewage system), and affects counties that plan under RCW 36.70A.040, county zoning and development control programs, and water and sewer providers. The bill passed the House on February 10, 2026 (96-0), passed the Senate on February 26, 2026 (48-0), and was first read in the House January 27, 2026. The extracted text does not include the prior version of RCW 36.70A.536 for direct comparison, the specific statutory language added or deleted, the definition text for "limited areas of more intensive rural development," any effective date, implementation deadlines, appropriations, or a filing/approval date.

If enacted, counties that plan under state growth law could be required or choose to allow small multiunit "middle housing" (up to four units per lot) wherever single-family homes are allowed in certain designated rural development areas and in urban growth areas, and they generally could not impose design or permit rules that are stricter than those for detached single-family homes. Practically, that means many counties will need to change local zoning ordinances and development rules, and they will have less discretion to apply extra local design controls; local permitting processes and environmental review would generally follow the same procedures used for single-family homes. The groups most directly affected are county planning and permitting departments, which will likely face work to update ordinances and apply the new standards, and public water and sewer providers, which must serve any newly authorized middle housing according to the bill’s service tests (public sewer or large on-site systems in rural limited areas, public sewer in nonrural limited areas, and water and sewer in urban growth areas). The bill increases the likelihood of additional demand on utility services and shifts regulatory options away from stricter local controls, but the text leaves out key implementation details (the exact designation of the rural areas, changes from prior law, and any effective date or funding to support implementation).