Cupertino Zoning and ADU Guide for Homeowners

Last updated November 13, 2026. Reviewed by the Cash Home Buyers CA team.

Cupertino says an ADU of 800 square feet or less is not limited by lot coverage, floor area ratio or open space rules, and that units under 750 square feet do not pay park, storm drain or school impact fees. This guide covers the ADU and accessory-structure rules a Cupertino homeowner is most likely to run into, how ADUs relate to a home sale, and what to do if a past owner built something without approval.

Cupertino ADU rules at a glance

Streamlined ADU size	Up to 800 sq. ft. (attached or detached)
Maximum size otherwise	850 sq. ft. for a studio or one-bedroom; 1,000 sq. ft. for two or more bedrooms
JADU	Up to 500 sq. ft., inside the existing or proposed home (not a garage), with at least an efficiency kitchen
Setbacks	As close as 4 ft from the rear and side property lines if 800 sq. ft. or less
Lot coverage, FAR, open space	Not applied to ADUs of 800 sq. ft. or less; applied to larger ADUs
Garage conversion	No replacement parking required
Impact fees	ADUs under 750 sq. ft. do not pay park, storm drain or school impact fees
Address	A detached ADU must have its own address
Contacts	planning@cupertino.gov; building@cupertino.gov

How many ADUs Cupertino allows

For a single-family property, the city describes a streamlined detached ADU of up to 800 square feet plus a JADU, for a total of two.

A separate FAQ explains that you may build any combination of a JADU, an attached ADU of up to 800 square feet and a detached ADU of up to 800 square feet, with no more than three total on the property.

The two pages describe the limits differently, so confirm your combination with the Planning Department before you design.

On multifamily property, the city describes up to two detached ADUs plus conversion of non-habitable space into ADUs equal to as much as 25 percent of the existing units, with a minimum of one. ADUs in multifamily developments are not limited by lot coverage, FAR or open space.

JADU requirements

A junior accessory dwelling unit is a unit of up to 500 square feet contained entirely within an existing or proposed home, converted from habitable living space.

The city lists these conditions: it must fit within the allowed 45 percent floor area ratio, it needs at least an efficiency kitchen, and the bathroom may be shared or separate. The owner must live in either the main home or the JADU.

A deed restriction must be recorded prohibiting sale of the JADU separately from the main home and holding the unit to JADU rules. A JADU cannot be combined with an attached ADU, or with a detached ADU over 800 square feet.

Garages, patios and second stories

You can build an ADU in a garage or covered patio if the structure meets the necessary size, height and setback rules and, for the main house, the FAR and lot coverage limits (excluding the ADU living area). Converting a garage does not require replacement parking.

A two-story ADU is allowed where you are converting part of existing second-story space. For height and setbacks on fences, sheds and other detached accessory structures, the city points homeowners to its planning staff at 408-777-3208.

Permits and fees

A building permit is required to build an ADU. The city publishes an ADU information sheet and a handout called Steps to a Completed ADU, and it lists typical building review timelines of about 10 days for each ADU review round once an application is complete.

Fees beyond the exemption for units under 750 square feet still apply, and the page lists the Cupertino Union School District for school fee questions. For process detail see our Cupertino building permits guide.

State ADU law behind the local rules

California law requires cities to approve qualifying ADUs through a ministerial process, which means staff check the project against objective standards rather than holding a discretionary hearing.

State law also sets minimums cities cannot override, including allowing an ADU of at least 800 square feet with four-foot side and rear setbacks and limiting impact fees on smaller units.

Cupertino’s published rules track those minimums, which is why the 800-square-foot and 750-square-foot figures appear on the city’s pages. Rules change often, so confirm the current ordinance before you rely on a number.

Zoning, ADUs and selling a Cupertino house

Buyers and lenders look closely at accessory units. A permitted, finaled ADU can add value, while an unpermitted garage conversion or backyard unit can complicate a sale. California sellers generally disclose known unpermitted work, and our statewide guide to selling as-is with unpermitted work explains the rules.

If your Cupertino property has a unit that was never permitted, you generally can legalize it, remove it, disclose it and discount the price, or sell as-is to a cash buyer. A quick checklist:

• Confirm in the permit portal whether the ADU, garage conversion or addition was permitted and finaled.
• Check the unit has its own address if detached, and that any JADU deed restriction is recorded.
• Ask Planning whether the unit meets current size and setback rules.
• Gather plans, inspection records and utility details.
• Compare the cost of legalizing with a no-repairs cash sale.

How to sell a house in Cupertino

1. Identify any accessory unit or addition and its permit status.
2. Collect permits, final inspections and any city notices.
3. Request a no-obligation cash offer for the property as it stands.
4. Choose your closing date.
5. Close with no repairs, permit cleanup or showings required.

Our local pages cover related situations in Cupertino, including selling as-is, selling fast and the cash offer process.

Frequently asked questions

How big can an ADU be in Cupertino?

The city says a studio or one-bedroom ADU can be up to 850 square feet and an ADU with two or more bedrooms up to 1,000 square feet, while streamlined ADUs are up to 800 square feet.

Do I pay impact fees on a Cupertino ADU?

The city says ADUs under 750 square feet do not pay park, storm drain or school impact fees. Larger units still do.

Do I need replacement parking for a garage conversion?

No. The city says replacement parking is not required when a garage is converted to an ADU.

How close to the property line can an ADU be?

As close as 4 feet from the rear and side lines if the ADU is 800 square feet or less.

Does the owner have to live on site?

The city lists owner occupancy for a JADU: the owner must live in the main home or the JADU.

Can I sell a Cupertino house with an unpermitted unit?

Yes. You can disclose it and sell as-is, including to a cash buyer.

More guides

• We Buy Houses in Cupertino
• We Buy Houses in Santa Clara County
• Santa Clara County Property Tax Guide
• Cupertino Building Permits Guide
• Cupertino Code Enforcement Guide
• All California Guides

Sources

• City of Cupertino: Accessory Dwelling Units
• City of Cupertino: ADU FAQ
• City of Cupertino: Sheds, Patios and Other Structures

This guide is general information from public sources, not legal advice. Confirm current rules with the city.