Mill Creek planners briefed on state middle-housing rules; staff seeks simpler ADU/density approach

Mill Creek Planning Commission members on March 20 heard a staff briefing on a package of code amendments intended to make the city comply with recent Washington state laws that require cities to allow “middle housing” types in single-family areas and expand accessory dwelling unit (ADU) allowances.

Staff focused on three state bills — HB 1110, HB 1337 and SB 5258 — and walked the commission through proposed changes to Titles 4, 14, 16 and 17 of the Mill Creek municipal code, including unit-lot subdivision procedures, administrative (staff) design review for middle housing, revised parking rules near frequent-transit stops and an increase in maximum ADU size from 800 to 1,000 square feet.

Why it matters: The changes would alter how many homes can be built on many residential lots, affect homeowner associations that restrict ADUs or “middle housing,” and change review processes for multi-unit infill. Staff said Middle Housing compliance must be submitted to the state commerce department later this spring, and the city is aiming to finish the local code edits and send them for certification.

Justin, planning staff, opened the presentation by defining middle housing: “Middle housing is a form of housing that's compatible with single family homes in scale and form,” and noted that roughly “almost 20% of the housing stock is actually middle housing” in Mill Creek. He told commissioners the city must adopt changes required by HB 1110 (minimum units per lot and streamlined review), HB 1337…