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Planning Commission forwards ADU ordinance overhaul to City Council, removes mandatory ADU parking and clarifies discretionary review
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Summary
The Planning Commission on Dec. 9 recommended City Council adopt comprehensive ADU ordinance updates to conform with HCD guidance and state law, eliminate mandatory off-street ADU parking citywide, and retain a limited discretionary-review path for atypical cases; commissioners also requested appeals remain to Planning Commission.
The San Mateo Planning Commission voted Dec. 9 to forward a comprehensive update to the city's accessory dwelling unit (ADU) ordinance to the City Council, incorporating California Department of Housing and Community Development (HCD) comments and local clarifications.
Associate planner Liz Gagliardi told the commission the draft contains two categories of changes: (1) amendments required to meet HCD and state law, and (2) additional objective, locally determined standards intended to improve usability. Key HCD-driven changes include a new ADU definitions section (including a multifamily-dwelling-structure definition aligned with state law), clearer rules for separate sale of ADUs by qualified nonprofit developers (Gov. Code citation noted), fee clarifications (no impact fee for ADUs under 750 sq ft; larger units pay proportional fees), and alignment of JADU size to a 500-square-foot maximum per HCD guidance.
Gagliardi said state law requires allowing a specified number of ADUs on single-family lots; the draft allows up to three ADUs (two ADUs plus one junior ADU) per single-family property in line with HCD direction. For multifamily properties, staff noted the draft implements changes tied to state law that can allow additional detached ADUs depending on the number of primary units.
On parking, staff proposed eliminating mandatory off-street parking requirements for ADUs citywide, noting that many parcels are already exempt under state rules (for example, properties near transit). To reduce potential front-yard overpaving, the draft also codifies voluntary parking provisions: up to two voluntary ADU parking stalls may be provided (including tandem stalls), existing driveways and curb cuts may remain, driveways can be widened to 20 feet, and covered parking within an ADU footprint can be permitted when it meets specified dimensional limits.
The draft preserves an "ADU Doctor" discretionary-review process for proposals that do not meet objective standards, while clarifying that discretionary review cannot be used to increase the maximum allowed floor area. Commissioners asked staff to keep the discretionary path available for reasonable site-specific exceptions and to tighten the findings language so exceptions are objectively justified. Several commissioners preferred that appeals from discretionary ADU decisions continue to go to the Planning Commission (and then Council) rather than to a city-manager designee; staff agreed to retain the commission appeals route.
The commission also directed a drafting clarification so that second-story decks or balconies associated with ADUs not face adjacent residential properties; commissioners agreed the rule should allow balconies that face streets, alleys, parks or nonresidential properties.
The Planning Commission voted to forward the ordinance to City Council with a desk amendment and with the commission's agreed edits (unanimous vote). Staff indicated the ordinance package will go to the council in January 2026 for next steps toward adoption.
What this means: If Council adopts the ordinance with the changes, property owners will see clearer, state-compliant ADU rules in San Mateo, fewer local parking barriers for ADU construction, and a preserved discretionary review option for atypical sites that need an exception.
