Two Detached ADUs in Cupertino (AB 956, 2027)
Plan Two ADUs in Cupertino: Free Site Assessment
Cupertino ADU rules today (2026)
From January 1, 2027, state law (AB 956) requires the City of Cupertino to approve up to two detached ADUs on a lot with a single-family home. Cupertino offers pre-approved detached ADU plans for lots on the Valley Floor, most of them under 800 sq ft. Here is how the new law and the city’s current ADU rules fit together.
Cupertino’s ADU rules are in Municipal Code Chapter 19.112, most recently amended by Ord. 25-2274 in 2025.
- Units allowed now: under its streamlined rules, the city’s ADU code allows up to three ADUs per single-family lot in combinations of attached, conversion, detached and JADU units. Confirm with the city which combinations apply to your lot. Non-streamlined projects allow one of each type.
- Size: streamlined new construction up to 800 sq ft. Non-streamlined units may be 850 sq ft (studio or one bedroom) or 1,000 sq ft (two or more). ADUs of 800 sq ft or less are exempt from lot coverage, floor area and open space.
- JADU: up to 500 sq ft, within the home’s habitable space, not a garage.
- Height: 18 ft for a streamlined detached ADU, or 20 ft within a half mile of transit for roof pitch. Two-story ADUs are allowed only by converting existing second-story space.
- Setbacks: 4 ft side and rear for ADUs of 800 sq ft or less.
- Parking: none for streamlined units.
- Pre-approved plans: detached models of 476, 495, 499, 674, 749 and 991 sq ft, for Valley Floor Zone parcels only.
State review of Cupertino's ADU rules
On April 24, 2025, the state housing department (HCD) issued findings on Cupertino’s 2024 ordinance. It said the code had not been updated for newer state laws on multifamily and unpermitted ADUs and kept a subjective “compatible” design standard. Where local rules are stricter than state law, state law applies.
Recent Axiom work
Professional photos from a recent Axiom Renovation full remodel and addition in Los Gatos.
What changes on January 1, 2027
AB 956 requires the city to approve up to two detached new-construction ADUs on a single-family lot. The city may cap each at 800 sq ft of living space and apply height limits; side and rear setbacks can be no more than 4 ft. Where two detached ADUs are built, a JADU need not be approved, and HOA rules cannot block or unreasonably restrict the units. Cupertino’s streamlined rules already allow up to three ADUs in combinations, so check with the city how AB 956 will be written into Chapter 19.112. Five of the six pre-approved plans are under 800 sq ft, which fits the size the city may set for two detached units. We confirm current rules as the city updates its code.
Planning two detached ADUs on a Cupertino lot
- Hillside and hazards: pre-approved plans are not available in hillside, fault-rupture, slope-instability or liquefaction areas. The city’s property lookup tool shows whether a lot is in the Valley Floor Zone.
- Neighborhood design: non-streamlined units follow added design standards in R1-e (Eichler), Monta Vista, RHS and R1-a areas.
- Equipment noise: an AC condenser sound worksheet is required.
- Fire: Santa Clara County Fire reviews ADU plans.
- Electrical: two units usually need a load calculation and often a service upgrade.
Building ADUs in Cupertino with Axiom
See our Cupertino ADU guide and Cupertino service area, read the AB 956 overview, or compare neighboring Sunnyvale and Saratoga.
Process
Our ADU Process
Step 1
Initial Consultation
We begin with a thorough initial consultation to understand your needs, assess your space, and discuss your vision, budget, and timeline.
Step 2
Planning and Design
At Axiom Renovation, we understand that the planning and design phase of an ADU project is crucial to its success. Our dedicated project managers will work closely with you to understand your goals, design ideas and budget for the project.
Step 3
Material Selection
We guide you through selecting high-quality materials that fit your design and budget, ensuring durability and aesthetic appeal.
Step 4
Demolition and Preparation
Careful demolition and preparation work are performed to ready the space for construction, minimizing disruptions and ensuring a clean work environment.
Step 5
Construction and Installation
Our skilled craftsmen handle the construction phase, including obtaining permits, scheduling appointments, and the actual construction and installation with precision, building the new space according to the approved design.
Step 6
Electrical and Plumbing Work
Licensed professionals conduct all electrical and plumbing work, ensuring everything is up to code and seamlessly integrated into the new ADU.
Step 7
Painting and Finishing
We pay close attention to detail during the painting and finishing stage, ensuring all surfaces are properly prepared and beautifully finished.
Step 8
Fixture and Appliance Installation
We expertly install all fixtures and appliances, ensuring they function correctly and fit perfectly with the overall design.
Step 9
Final Touches and Clean-Up
Final touches are added, and a thorough clean-up is performed, leaving your new space pristine and ready for use.
Step 10
Final Walkthrough and Client Satisfaction
We conduct a final walkthrough with you to ensure every detail meets your expectations and address any remaining concerns, ensuring your complete satisfaction.
Cupertino Two-ADU FAQ
Can I build two detached ADUs in Cupertino?
From January 1, 2027, AB 956 requires the city to approve up to two detached, new-construction ADUs on a lot with a single-family home, if the project meets objective standards. Cupertino’s streamlined rules already allow up to three ADUs in combinations; confirm with the city which combinations apply before 2027.
How large can each ADU be in Cupertino?
Streamlined new construction can be up to 800 sq ft, and units of that size are exempt from lot coverage and floor area. Under AB 956, the city may limit each of two detached ADUs to 800 sq ft of living space.
How tall can a detached ADU be in Cupertino?
18 ft for a streamlined detached ADU, or 20 ft within a half mile of transit. A two-story ADU is allowed only by converting existing second-story space.
Does Cupertino have pre-approved ADU plans?
Yes. Detached models range from 476 to 991 sq ft, for Valley Floor Zone parcels only. Hillside and geologic hazard areas are excluded.
Is there a noise rule for ADU equipment in Cupertino?
Yes. An AC condenser sound worksheet is part of the ADU submittal.
Who builds two-ADU projects in Cupertino?
Axiom Renovation designs, permits and builds ADUs in Cupertino and is planning two-unit projects for 2027. Call 408-702-2022, Monday to Friday, 9 am to 5 pm.
Sources: AB 956 (Quirk-Silva), signed September 29, 2026, effective January 1, 2027, as summarized by Brownstein Hyatt Farber Schreck and California YIMBY. This page is general information, not legal advice. Local rules change; we confirm current requirements with the city for every project.