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Permit guides
ADU Permits in Cupertino: a Homeowner's Guide
What you can build, which permits you need, and how Cupertino’s pre-approved ADU plans actually work — in plain language.
Last updated October 2026. Rules change; always confirm current requirements with the city or county before you build.
Who handles your permit
Cupertino’s ADU permits go through the Community Development Department. Building: (408) 777-3228, permitcenter@cupertino.gov; Planning: (408) 777-3008, planning@cupertino.gov. Applications are filed electronically — ProjectDox or email — per the residential plan review workbook. Know this up front: Cupertino rejects incomplete submittals at intake.
What you can build
State law sets the baseline; Cupertino’s ADU ordinance — updated in 2025 after a state housing department review — applies the local details:
1,200 sq ftMax for a detached ADU
750 sq ftADUs over 750 sq ft may owe park and school impact fees
~15 daysTypical initial Standard Review for an ADU or JADU, in business days
4 ftMinimum rear and side setbacks for detached ADUs
16 ftHeight limit for most detached ADUs
Valley FloorPre-approved ADU plans are only available in this zone
One ADU plus one JADU is allowed per single-family lot, and there is no minimum lot size under state law.
Pre-approved plans — with one big asterisk
Cupertino has offered a pre-approved ADU plan program since 2019: submit the Pre-approved Master Plan Package plus a boundary survey and a site plan (and outdoor condenser specs with the AC sound rating worksheet, if included) — the structural design is already checked. The catch is geography: pre-approved plans work only for parcels in the Valley Floor Zone. Parcels in fault rupture, slope instability, hillside, or liquefaction/inundation areas are excluded and need full site-specific review. And even with a pre-approved design, planning, fire, public works, and the local sanitary district still review the project.
What goes into the submittal
- Complete digital package: architectural plans, structural calculations stamped and signed by a licensed professional, and Title 24 energy compliance forms in the plan set.
- Geotechnical soils investigation report, stamped and signed (2 copies) — routine in Cupertino’s seismic hazard areas.
- Lot/boundary survey and/or horizontal control plan; residential CalGreen checklist; and the city’s Best Management Practices (BMP) sheet in all plan sets.
- AC condenser specs plus the AC Unit Sound Rating Worksheet, if applicable.
- Owner-Builder Disclosure (owners applying for their own permit) and the Hazardous Materials Questionnaire.
- Sewer clearance from the applicable sanitary district — Cupertino Sanitary District or Sunnyvale Sanitary District, depending on the address.
Where applications usually get stuck
- Rejected submittals. Anything incomplete is turned away — the review clock never starts.
- Seismic zone surprises. Hillside and hazard-area parcels need full geotechnical review, adding cost and time that valley-floor lots avoid.
- Second-story privacy rules. Window alignment and privacy protection requirements include planting plans with species and distances, backed by an arborist or landscape architect affidavit.
- Fees over 750 square feet. The city’s guidance says park and school fees may apply to ADUs over 750 sq ft — a real line item on larger units.
- HOA letters. The application asks for an HOA approval letter — CC&Rs can’t prohibit an ADU under state law, but chasing the letter can still slow the file.
Not sure where to start? That’s the part we do. We look at your property, map the requirements, coordinate the plans and specialists, and manage the submittal and corrections — one point of contact.