Shoreline adopts development code and zoning map updates, including ADU size, tree-retention and hardscape limits

The Shoreline City Council on Monday adopted Ordinance 1027, approving the updated zoning map and a package of development-code amendments intended to implement the city’s 2024 comprehensive plan and state law changes (including middle-housing requirements).

The ordinance and its associated attachment(s) include a substantial set of changes and multiple council amendments adopted during the meeting. Key outcomes adopted by the council include:

- ADU size: Council raised the maximum size for accessory dwelling units from 1,000 to 1,200 square feet in the NR1–NR3 residential zones, and clarified counting rules so a property may total up to three dwelling units under the code (primary plus ADUs) depending on zoning allowances.

- Density and bonuses: Council adopted language to treat ADUs as units that count toward maximum density; a separate amendment clarified that the maximum unit count is explicit (for example, three units) regardless of whether units are configured as principal units or ADUs.

- Impervious surface (hardscape) limits: Council adopted a 50% maximum hardscape cap in NR3 (the highest-density residential zone under this code package) and maintained more conservative caps in NR1 and NR2 relative to the draft staff proposal. Council members said the limits aim to balance increased housing capacity with stormwater, tree canopy and neighborhood character concerns.

- Tree retention and fees: The council approved a 35% citywide retention target for “significant trees” (trees 6 inches DBH and larger) in applicable development contexts and adopted a citywide fee-in-lieu for removal of very large trees (24 inches DBH or larger) consistent with the city’s 2025 fee schedule (staff noted the current fee schedule lists $9,000 per tree and may require fee schedule cleanup if code language is finalized).

- Neighborhood commercial uses: The council adjusted rules allowing small commercial uses in residential zones (neighborhood-serving commercial). The permitted maximum square footage in some zones was raised (ADUs and small commercial were discussed together); council required location, frontage and parking considerations in other amendments.

The planning and community development director, Andrew Bauer, presented the draft ordinance and summarized staff and planning commission recommendations. Staff noted some amendments were required to align the code with state law and the adopted comprehensive plan zoning map; other changes were council-initiated. Senior planners Sierra Carson and Steve Safran were available for technical questions.

Public comment was extensive on tree preservation, stormwater and neighborhood character. Kathleen Russell, speaking for the Tree Preservation Code Team, described the current code as allowing a low retention rate and urged support for Amendment 9 to set retention at 35% to protect large trees. Multiple residents and advocates pressed council to prioritize mature-tree preservation and reduce hardscape allowances.

Council debate covered multiple topics: balancing housing supply goals with tree canopy preservation and stormwater risks; whether to allow larger ADUs to increase housing affordability and rental options; how to measure and treat pervious materials for hardscape calculations; and the limits or waivers for frontage improvements when properties convert to different uses. Several staff-proposed cleanups and technical amendments were adopted as a batch.

The council approved the ordinance as amended by a recorded vote of 6–0. Staff signaled there will be further code work and a separate, more comprehensive tree-code review later in 2025.