Mountlake Terrace planners weigh Middle Housing code changes, set expedited drafting schedule

Mountlake Terrace Planning Commission members on March 24 reviewed proposed development-code amendments aimed at implementing Washington state's HB 1110 middle-housing requirements and gave staff direction to prepare a draft for submittal to the state Department of Commerce.

The discussion, led by consultants and city planning staff, covered lot-area minimums, how many units can be allowed per lot in low-density zones, whether to use lot-coverage or floor-area-ratio (FAR) to scale buildings, height and rear-yard limits for accessory dwelling units (ADUs), and parking and driveway standards. Staff scheduled a community open house for March 26 and said a draft must be ready for Commerce review in about 10 days; the commission will return April 14 for a workshop and the city council will be briefed later in the process.

Why it matters: The code changes are intended to comply with the state law that requires jurisdictions to allow middle-housing types on lots currently zoned for single-family houses. The decisions commissioners make on metrics such as lot coverage, FAR, setbacks and parking will shape how much and what type of housing — townhomes, duplexes, small cottages, stacked flats or ADUs — can be built in Mountlake Terrace and affect the relative feasibility and market price of new units.

Consultants opened by asking for policy direction rather than presenting final rules. "Today our goal is to seek more guidance on some of the housing types and initial standards," Mackenzie, a consultant to the project, told the commission. Heidi Oian, an architect and urban designer with the consultant team, summarized the firm's draft approach: "So tonight, we're going to propose initial development standards," she said, then walked commissioners through tables for lot area, unit counts per lot, lot coverage, height and setbacks.

Key proposals and findings presented - Minimum lot area: Staff proposed keeping the city's current lowest residential minimum of 4,800 square feet as the baseline for how unit counts are calculated. - Units per lot: The draft aligns with HB 1110's tiered approach: R-1 would allow 2 units per lot; R-2 would allow 4 units per lot (a double lot, 9,600 sq ft, would be treated as two 4,800-sq-ft lots). Consultants noted the draft still needs finer tuning on R-3 and R-4 densities for larger parcels. - Affordable-unit bonus: Consistent with the state requirement discussed, consultants proposed a bonus allowing more units (for example, allowing 4 units on a lot when one is kept affordable) and discussed scaling bonuses by percent affordable when projects exceed four units. - Scale control — lot coverage vs. FAR: Consultants tested both approaches and presented example "test fits." They reported that many existing Mountlake Terrace single-family footprints use relatively low structural lot coverage but that FAR captures both height and footprint effects more finely. Commissioners did not make a final choice, and staff said the commission must give a leaning (lot-coverage tables, a standard FAR, or a hybrid approach) before staff drafts the code. - Height and ADUs: The draft would step heights up from R-1 to R-4; R-4 would allow up to four stories. The team proposed smaller maximum heights for detached ADUs in R-1 and R-2 (25 feet) and 30 feet in R-3 and R-4. Consultants reminded the commission that state rules set a minimum accessory-dwelling allowance (the presentation cited the state requirement that jurisdictions allow ADUs of at least 1,000 square feet). - Setbacks: Staff proposed reduced front setbacks (proposed 10–15 feet in places) while retaining larger rear-yard setbacks (15–20 feet). They suggested an 8-foot side setback where pedestrian access and service are required to avoid narrow unusable side yards. - Parking and driveways: Consultants reviewed the state statute limiting what local governments can require and proposed minimum on-site parking of 1 stall per unit in R-1 through R-3 and 0.75 stalls per unit in R-4, with a 0.25-space reduction as a possible bonus for projects providing affordable units or tree retention. They proposed controlling driveway widths and limiting the percentage of a building facade taken by garage doors (staff tested a 50% facade maximum and narrower curb-cut widths such as 12 feet per 50 feet of lot frontage) to protect the pedestrian environment. - Feasibility signals from test fits: The consultant team said detached large single-family homes remain the most feasible product type at current prices; side-by-side fee-simple townhomes become competitive at roughly six units on a site; small multiplexes (four- to six-plexes) and stacked flats were generally harder to make financially feasible without additional incentives, density or parking relief.

Commissioner reactions and concerns Commissioners pressed staff on trade-offs between preserving open space, tree retention and building scale. Several members said they wanted standards that reduce garage-dominated frontages and encourage porches or habitable front facades. Commissioner Morgan (Planning Commissioner) said, "I'd like to make a decision rather than guessing or saying what I want to happen," urging the commission to give clear direction to staff. Commissioner Landis (Planning Commissioner) said he was inclined to "fall back on the proposal" presented by staff, given the level of analysis provided.

Other recurring concerns included: - Whether lot-coverage reductions or FAR would better prevent single-unit footprints from growing while still enabling middle housing. - The risk that investors would buy new for-sale middle housing and convert units to high-priced rentals, reducing owner-occupancy and affordability; consultants said patterns vary and that supply increases are a more reliable long-term moderating force than local controls on tenure. - The difficulty of getting stacked rentals and condo conversions to pencil under current liability and construction-cost norms; consultants flagged state-level condo liability and noted other states are only slowly changing their legal environments. - The trade-off between on-site parking and usable open space: layouts that keep cars on sites can consume the ground plane, while moving parking below-grade or to structured solutions is costly and typically feasible only at larger scales.

Next steps and schedule Staff confirmed a community open house on Wednesday (March 26) with a short presentation at 6:30 p.m. and interactive boards to gather public preferences on trade-offs between trees, open space and density. Consultants said they will: complete a draft code for submission to the Washington State Department of Commerce in roughly 10 days, return to the Planning Commission on April 14 for another workshop, brief the city council after that, hold a May 19 workshop to present a final code, and bring an adoption package to the commission and council near the end of May.

No formal motions or votes were taken on the draft tables; the session resulted in direction to staff to produce a complete draft code that reflects the commission's preferences and the technical test-fit work, to circulate the draft for public comment, and to submit it to Commerce for review in the short timeline required by state law.

The meeting included detailed visual test fits and numeric examples staff said they would include in the written draft and public materials. Consultants also said they are conducting interviews with developers who build in Mountlake Terrace and nearby cities to refine feasibility assumptions before finalizing standards.

Commissioners asked staff to circulate a written summary of the options discussed so they could annotate it and speed the drafting process. The commission set a follow-up workshop on April 14 and a public open house March 26. The code and the direction given are framed explicitly as drafts to be refined; no final regulatory changes were adopted at the March 24 meeting.