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Permits & plan-check · San Mateo · City of San Mateo Community Development

San Mateo ADU permits — what plan-check really looks like

Every San Mateo ADU permit runs through City of San Mateo Community Development. This is the realistic, project-manager view of that process — submittal package, plan-check rounds, the comments that come back most often, fees that hit before construction, and what separates a first-pass approval from a five-month round trip.

City-specific deep dives

City of San Mateo Community Development submittal package

A clean first submittal in San Mateo includes: site plan with setbacks and FAR calculation, architectural set (floor plans, elevations, sections, roof plan), Title 24 energy compliance, structural calcs and details, MEP plans, and the ADU-specific application packet. Missing any one of these adds two to four weeks of plan-check delay — not because plan-check is slow, but because the package goes back to the design team.

First-pass comments — the predictable ones

San Mateo plan-checkers consistently flag the same items: setback dimensioning, fire-separation details where the ADU is close to the main house, parking math (or its waiver), egress window sizing, Title 24 documentation gaps, and missing structural connection details. A disciplined design set anticipates these. Most second-pass turnarounds are avoidable.

Fees, school fees, and utility connections

Plan-check fee, building permit, mechanical/electrical/plumbing permits, school district impact fee (if applicable), water capacity fee, and sewer capacity fee. In San Mateo, these collectively land between $14,000 and $28,000 depending on ADU size and existing utilities. We model this at feasibility so the homeowner sees a real total, not just construction cost.

How long it actually takes in this jurisdiction

City of San Mateo Community Development plan-check averages 3–5 months from submittal to permit issuance in 2026 — assuming a clean package and responsive comments. Hillside, coastal, HPOZ, or special review overlays add 4–10 weeks. We tell the homeowner the realistic window at feasibility, then track it weekly.

San Mateo · Permits & plan-check

Questions San Mateo homeowners ask about permits

Direct answers, San Mateo-specific.

  1. Are San Mateo ADU rents really that strong?
    Yes — Peninsula tenant demand from the biotech and tech corridors keeps 1BR ADU rents in the $2,800–$3,600 range.
  2. Do I need flood-elevation drawings?
    Only if your parcel sits in FEMA Zone AE or VE — mostly the eastern edge. We pull FEMA layers at feasibility.
  3. Does San Mateo have unique requirements that affect permits?
    Yes — City of San Mateo Community Development sets the local rules, and San Mateo has its own plan-check rhythm. The realistic numbers above reflect 2026 San Mateo conditions, not statewide averages.

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