Commission discusses limits on external accessory dwelling units and detached accessory structures; no action taken

The Planning Commission held an extended discussion on standards for unoccupied accessory structures and external accessory dwelling units (ADUs) — specifically how the code treats height, roof pitch, "half story" definitions (the kick wall), basements and setbacks. Commissioners and staff discussed concerns that current definitions allow builders to create large, livable structures behind existing homes that function as separate homes.

Planning staff outlined current rules: the code currently sets a 20-foot height for pitched roofs and 16 feet for flat roofs, permits a "one-and-one-half story" in some cases, and defines a basement or kick wall that extends less than 4 feet above grade as not constituting an extra story. Staff said those combined standards can allow a basement plus one-and-a-half stories that effectively produces a multi-level, fully livable structure. "So there's been difficulties interpreting the half story, with how we regulate that," staff said.

Commissioners raised privacy, windows facing neighboring yards, code-enforcement and the potential for owners to build what amount to separate houses on long, deep lots. Options discussed included: - Define "flat" and "pitched" roofs by a building-code reference, not an informal standard, so designers cannot exploit ambiguous pitch language; - Eliminate the half‑story allowance for flat roofs (e.g., allow only one story above grade for flat roofs) or eliminate half stories entirely; - Allow basements but not both basement and an upper livable level (i.e., not above and below simultanously); - Limit ADU livable area (staff noted an existing threshold of 900 sq. ft. or 13% of lot area, whichever is larger) or reintroduce a fixed maximum livable area for ADUs to prevent creation of full second homes; and - Use setbacks, window-location rules and zero-setback criteria (no openings on the lot-line) to protect privacy.

Commissioners repeatedly emphasized that clear, simple standards reduce enforcement burden and limit opportunities to circumvent intent. Several commissioners suggested treating detached accessory structures and external ADUs differently because livable units have distinct fire, egress and privacy implications; others favored a consistent approach but with additional livability limitations for ADUs.

No formal motion or vote was taken; staff said they would refine code language and return with proposed definitions and alternative standards (for example: definitive flat/pitched roof language, removal of half story allowances for flat roofs, and options for capping livable square footage or restricting basements).