On single-family lots in Cupertino, you can build one ADU (attached or detached) and one JADU. Single-family zones promote additional housing without altering neighborhood character.

Duplex and multifamily properties can add ADUs by converting non-livable space. Up to 25% of existing units may be converted. Detached ADUs may also be permitted depending on lot configuration.

Yes, Cupertino allows Junior ADUs up to 500 square feet. A JADU must be within the existing single-family residence and requires a separate entrance and efficiency kitchen. Owner-occupancy is required for properties with JADUs.

Cupertino does not have a separate guest quarters classification. Any secondary living space with kitchen facilities is classified as an ADU.

Detached ADUs up to 800 square feet qualify for streamlined ministerial approval ("Streamlined Units" or "66323 Units"). Larger ADUs up to 850 square feet (one bedroom) or 1,000 square feet (two+ bedrooms) are allowed but must comply with the Accessory Structure Ordinance and architectural matching requirements.

Attached ADUs are limited to 850 square feet for one-bedroom units or 1,000 square feet for two or more bedrooms. They cannot exceed 50% of the existing primary dwelling's floor area and must meet FAR and lot coverage requirements.

Yes. "Streamlined Units" (800 square feet or less with 4-foot setbacks and 18-foot height) are exempt from lot coverage, FAR, and open space requirements per state law.

Streamlined ADUs (800 square feet or less) can reach 18 feet in height. Larger detached ADUs may have different height limits depending on zoning. Attached ADUs follow the primary dwelling's height regulations.

Detached two-story ADUs are generally not permitted in Cupertino. Single-story designs within the 18-foot height limit are standard. Attached ADUs may have different configurations depending on the primary dwelling.

Detached ADUs and attached ADUs less than 800 square feet require minimum 4-foot rear and side setbacks. Front setbacks follow the underlying zoning. On corner lots, street-side setbacks are modified to 4 feet, but ADUs cannot encroach into required corner triangles.

Building separation requirements follow underlying zoning and California Building Code standards for fire safety and access.

Cupertino processes ADU permits within 60 days as required by state law. Streamlined Units meeting all criteria receive ministerial approval without design review. Overall, expect 2-4 months from application to permit issuance.

Permit costs vary based on project scope and construction valuation. ADUs under 750 square feet qualify for reduced or waived impact fees. Use the Santa Clara County ADU Calculator to estimate costs.

Cupertino does not routinely require soils reports or building surveys for standard ADU projects. Properties in special zones or with unusual conditions may require additional documentation.

Cupertino requires one parking space per detached ADU in most cases. However, parking can be waived if the property is within half a mile of public transit or in a historic district. Conversion ADUs and JADUs never require parking.

If converting a garage to an ADU, replacement off-street parking must be provided unless you qualify for a transit exemption. This is more restrictive than some neighboring cities.

If parking is required, off-street parking can be arranged in tandem or within property setbacks as long as access remains safe. Driveways may qualify depending on configuration.