Council to consider state‑mandated housing code updates next week; staff says Mill Creek largely compliant

City planning staff presented ordinance language on May 27 to update Mill Creek’s municipal code to comply with recent Washington state housing laws, including requirements for middle housing, accessory dwelling units (ADUs), unit‑lot subdivisions and building conversion density bonuses.

“HB 1110, the middle housing bill, requires that we allow at least two dwelling units per lot and provide administrative design review,” the city’s planner Horn told the council. Horn said the package also implements HB 1337 (ADU changes), HB 5258 (unit‑lot subdivision) and the recently enacted Senate Bill 5559 clarifications. The draft also aligns the local definition of boarding houses with the state code and allows required coliving/boarding‑house uses in zones that permit at least six dwelling units.

Horn said Mill Creek is largely compliant with most requirements because some zones already met the new minimum densities; the changes mainly affect the neighborhood residential zone and a small portion of the city not covered by homeowner association restrictions. The staff report noted that HOAs can bar middle housing and ADUs if restrictive covenants predated July 23, 2023.

Council and staff discussed whether to delay the unit‑lot subdivision section pending the final text of SB 5559. Horn said the current draft is consistent with the law as passed and could be isolated and amended later if needed. At least one councilor asked to defer final adoption to allow a council member more time to review; staff said the council has until June 30 for the core middle‑housing and ADU changes and will place the ordinance on the Old Business list for action at the next meeting.

Staff said the Department of Commerce has reviewed the amendments and did not raise objections. No vote was taken; staff will return with the ordinance for adoption at the council’s next meeting.