California ADU rules · Santa Clara County
Can I Build an ADU in Cupertino?
Yes — you can build an ADU in Cupertino. California's statewide ADU law requires every city, including Cupertino, to approve a qualifying accessory dwelling unit by right, plus a junior ADU (JADU) on a single-family lot. What varies city to city are the local specifics below.
Can you build one?
ADUs allowed
CA state lawYes — by right
ADUs and JADUs are allowed by right in all residential and mixed-use zones; ministerial approval, no hearing.
Units on a single-family lot
Local ruleUp to three units in any combination of: 1 attached ADU, 1 detached ADU, 1 conversion ADU, and/or 1 JADU; no more than three total per lot
Allows up to three total units per single-family lot, exceeding state baseline.
Units on a multifamily lot
Local ruleConversions: at least one or up to 25% of existing units; Detached: up to 2 for proposed multifamily, up to 8 for existing multifamily, not to exceed number of existing units
Detached ADUs capped at 2 (proposed) or 8 (existing) per multifamily lot.
Junior ADU (JADU)
CA state lawAllowed
Up to 500 sq ft, within the walls of an existing single-family home (single-family lots only).
Size & height
Max detached ADU size
Local rule1,000 sq ft
Detached ADUs: 850 sq ft (studio/1-bed), 1,000 sq ft (2+ beds); 800 sq ft for streamlined ADUs.
Max attached ADU size
Local rule50% of primary, >=850 (studio/1-bed), >=1,000 (2+ beds)
Attached ADUs: up to 50% of primary dwelling, but not less than 850/1,000 sq ft.
Guaranteed minimum size
CA state law800 sq ft
An 800 sq ft ADU must be allowed regardless of FAR/lot-coverage caps; a city also cannot cap an attached ADU below 850 sq ft (1,000 for 2+ bedrooms).
Max JADU size
CA state law500 sq ft
Max height
Local rule18 ft
Detached ADU: 18 ft base; up to 20 ft near transit; attached ADU: 25 ft or primary dwelling height, whichever is lower.
Setbacks
Side setback
CA state law4 ft
A city cannot require more than 4 ft side or rear setback; conversions of existing structures are exempt.
Rear setback
CA state law4 ft
Front setback
Local ruleNo explicit minimum for ADUs ≤800 sq ft; otherwise, per underlying zoning district
ADUs ≤800 sq ft exempt from front setback minimum.
Separation from main house
Local ruleNone required
No specific minimum separation required for detached ADUs.
Parking
Parking required
Local ruleNone
No parking required for streamlined ADUs; non-streamlined may require 1 space if primary does not meet minimum.
Transit parking exemption
CA state lawYes — no parking required near transit & for conversions
No parking may be required within ½ mi walking distance of transit, in a historic district, for an ADU within an existing structure, within one block of car-share, or in certain permit-parking areas.
Garage-conversion replacement parking
Local ruleNot required
No replacement parking required for garage/carport conversions.
Approval, timeline & cost
Approval path
CA state lawMinisterial (by right)
No public hearing or discretionary design review for a qualifying ADU.
Approval timeline
CA state law60 days
The agency must act within 60 days of a complete application — and the ADU is deemed approved if it does not.
Owner-occupancy
Local ruleOnly for a JADU
Owner-occupancy required for JADUs only.
Impact-fee waiver
Local ruleWaived under 750 sq ft
Impact fees waived for ADUs/JADUs <750 sq ft.
Permits required
Local ruleBuilding permit
Building permit required for all ADUs/JADUs; legalization allowed for pre-2020 units.
Cupertino-specific factors that can change the answer
State law sets the floor, but these local conditions often decide whether a specific parcel works.
Residential Hillside (RHS) and special districts
Design standards apply to ADUs in hillside and special zoning districts.
Cupertino allows up to three ADU/JADU units per single-family lot and sets local maximum sizes for detached and attached ADUs above the state minimum. Hillside areas have additional design standards.
Frequently asked questions
Can I build an ADU in Cupertino?
Yes. California's statewide ADU law requires Cupertino to approve a qualifying accessory dwelling unit ministerial (by right), plus a junior ADU (JADU) on a single-family lot.
How big can an ADU be in Cupertino?
A detached ADU of at least 1,000 sq ft must be allowed, and an ADU of 800 sq ft can never be zoned out by floor-area or lot-coverage limits. A JADU can be up to 500 sq ft.
What are the setback requirements for an ADU in Cupertino?
Side and rear setbacks are limited to 4 ft. No explicit minimum for ADUs ≤800 sq ft; otherwise, per underlying zoning district.
Is parking required for an ADU in Cupertino?
None. No parking can be required within ½ mile of transit, for conversions, or for units inside the primary home. When a garage is converted, replacement parking is not required.
How long does ADU approval take in Cupertino?
A complete application must be acted on within 60 days, with ministerial (by right) — no public hearing or discretionary design review for a qualifying ADU.
Do I have to live on the property to build an ADU in Cupertino?
Owner-occupancy: only for a jadu. ADUs under 750 sq ft are also exempt from impact fees.
Sources
- Cupertino Municipal Code Chapter 19.112 (Ord. 25-2274, effective 2025)
- Table 19.112.030A
- Table 19.112.040
- §19.112.040
- Cal. Gov. Code §§ 66310–66342 (ADU Law)
- HCD 2025 Accessory Dwelling Unit Handbook
- Cal. Gov. Code § 66317 (ministerial approval, 60-day deadline)
- Cal. Gov. Code § 66333 (junior ADUs)
- Cal. Gov. Code § 66321 (size minimums & height)
- Cal. Gov. Code § 66323 (by-right ADU/JADU, 800 sq ft, 4-ft setbacks)
- Cal. Gov. Code § 66322 (ADU parking; § 66334 covers JADU parking)
Last updated 2026-06-25. This is an AI-assisted summary of Cupertino's ADU rules, drawn from its published ordinance and California ADU law — general information, not legal advice, and it may be incomplete or out of date. Verify the controlling rule for your specific parcel with Cupertino Planning before relying on it.
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