San Mateo County committee advances draft design‑review ordinance; debates ADU rules, rooftop decks and slope limits

Camille, a county planning staff member, told the San Mateo County Design Review Committee on Oct. 9 that planning staff will circulate a revised draft of the county's design review ordinance update and present that draft to the Planning Commission at a meeting scheduled for Oct. 22.

"I'm posting it. I'm sending it to the FCC to post on their website for the 10/22 meeting," Camille said, adding she would also send the draft to committee members ahead of the Planning Commission hearing.

Why it matters: The draft ordinance would create objective design standards meant to apply across design review districts and to both ministerial projects and discretionary projects in the coastal zone. Committee members spent most of the meeting reviewing discrete design standards for ADUs, privacy and windows, rooftop decks, materials and finish, grading and hardscape limits, and slope-sensitive rules for garages and site excavation.

Key outcomes and discussion points

Process and next steps: Camille said staff will prepare a revised, digital copy of the ordinance update one week before the Planning Commission meeting so it can be posted for public review. The committee's recommendations are advisory; the Planning Commission and Board of Supervisors will consider final action.

ADU setbacks, rooftop decks and sill heights: Committee members agreed to retain a prohibition on rooftop decks where an ADU has a nonconforming side setback and to require a minimum sill (window) height intended to protect privacy. The sill height discussed was 6 feet 6 inches. The committee discussed exceptions for egress windows and agreed that, where an egress window must be lower than the sill standard, the window should be opaque to protect privacy.

Building pads and prefabricated ADUs: The draft included a…