WA SB5471

Counties planning under the Growth Management Act may authorize middle housing types on parcels zoned for single-family residences in designated urban growth areas and limited areas of more intensive rural development, with a maximum of 4 residential units per lot

Middle housing standards cannot be more restrictive than those for detached single-family residences, though counties may apply objective development regulations like setbacks, lot coverage, stormwater, and tree retention requirements

Middle housing in limited areas of more intensive rural development must be served by existing sewer service; middle housing in urban growth areas must be served by both water and sewer services

County actions implementing these middle housing provisions are exempt from administrative or judicial appeals under the State Environmental Policy Act (SEPA) and the Growth Management Hearings Board

Effective date is July 27, 2025; passed with strong bipartisan support (Senate 48-0, House 90-4)