San Mateo Advances ADU Reforms: No Parking Mandate, Faster Appeals

SAN MATEO, CA — San Mateo is poised to streamline construction of accessory dwelling units with changes that eliminate parking mandates, clarify height rules and reroute appeals away from the City Council.

At its Jan. 26 meeting, the council introduced an updated ADU ordinance to align with state law and respond to local experiences since the city’s last major update in 2022.

Associate Planner Elizabeth Gagliardi reported that San Mateo has issued about 380 ADU permits under the current rules, which she said is more than any other jurisdiction in San Mateo County, and expects similar production to continue.

One of the most significant changes is on parking. A map presented to the council showed that nearly all of San Mateo already falls under state rules that prohibit cities from requiring off‑street parking for ADUs near transit.

“To ensure equitable application of parking standards,” Gagliardi said, the updated ordinance would eliminate all parking requirements for ADUs but allow owners to add up to two voluntary spaces with more flexible designs, including tandem parking and slightly wider driveways.

Councilmember Rob Newsom supported the reforms but raised a related concern about on‑street congestion in permit zones. He suggested that as the city revisits its residential parking permit program they should make sure that an ADU counts as the accessibility of having more permits so households adding units are not locked out of street parking.

The ordinance also adjusts height limits for detached ADUs. Current local rules cap height at 16 feet to the top plate and 24 feet to the roof peak. The new standard keeps the 24‑foot peak but allows an 18‑foot plate height so that standard two‑story ADUs can be approved ministerially.

On appeals, the council declined a Planning Commission suggestion to route discretionary ADU decisions to the commission and then to the council. Instead, they kept the staff's proposal for appeals to go to the city manager or a hearing officer.

“I don’t want to do anything to slow down the process of building more ADUs and building more housing,” Newsom said, citing concerns that council appeals could take many months.

Councilmember Lisa Diaz Nash agreed that complex technical appeals are better handled administratively. She said she did not believe this body is the right body to do appeals on ADUs.

The council also adopted two planning commission recommendations refining language on when discretionary ADU review applies and tightening privacy rules so small second‑story decks approved without hearings cannot face adjacent residential properties.

The updated ADU ordinance will return for a second reading and final adoption at a future meeting.