Two Detached ADUs in Sunnyvale (AB 956, 2027)
Plan Two ADUs in Sunnyvale: Free Site Assessment
Sunnyvale ADU rules today (2026)
From January 1, 2027, state law (AB 956) requires the City of Sunnyvale to approve up to two detached ADUs on a lot with a single-family home. Sunnyvale already has a streamlined path for new ADUs up to 800 sq ft that needs only a building permit. Here is how the new law and the city’s current ADU rules fit together.
Sunnyvale’s ADU rules are in Municipal Code Chapter 19.79 (Ord. 3240-25, April 2025, amended by Ord. 3258-26 in July 2026).
- Units allowed now: the city’s ADU code allows one conversion ADU, one new-construction ADU and one JADU on a single-family lot, with only one attached-type unit.
- Size: new construction from 150 to 1,000 sq ft; streamlined units up to 800 sq ft. A JADU may be up to 500 sq ft.
- Height: 16 ft detached, or 18 ft within a half mile of transit, plus 2 ft for roof pitch. Two stories maximum.
- Setbacks and separation: 4 ft side and rear. Non-streamlined detached units stay 5 ft from the main house and other accessory buildings.
- Parking: none required, and no replacement for removed covered spaces.
- Process: streamlined units need only a building permit; larger units add a ministerial Miscellaneous Plan Permit. The city’s handout says typical review is 2 to 4 weeks.
- Plan gallery: pre-approved designs are listed in the city’s ADU Plan Gallery.
State review of Sunnyvale's ADU rules
In December 2022, the state housing department (HCD) found Sunnyvale’s 2021 ordinance out of compliance. It flagged a one-ADU limit, entry rules, a front-setback ban, an 800 sq ft minimum and JADU rules. New ordinances followed in 2023, 2025 and 2026. 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. Sunnyvale’s streamlined 800 sq ft unit already matches the size the city may set for two units. The July 2026 amendment touched the unit-count and timeline sections, and the city will need to update Chapter 19.79 again for AB 956. The 5 ft separation and front setbacks for larger units will matter when placing two buildings. We confirm current rules as the city acts.
Planning two detached ADUs on a Sunnyvale lot
- Protected trees: a streamlined ADU needs no separate tree removal permit; trees are reviewed with the building permit. Larger units need a replacement tree for each protected tree removed.
- Sprinklers: required if the main house has them. A detached unit beyond 150 ft of hose reach also needs them.
- Second-story windows: within 20 ft of the rear line or 7 ft of a side line, windows need 5 ft sills or opaque glass.
- Fire separation: detached units must meet building-code fire separation between structures.
- Electrical: two units usually need a load calculation and often a service upgrade.
Building ADUs in Sunnyvale with Axiom
See our Sunnyvale ADU guide and Sunnyvale service area, read the AB 956 overview, or compare neighboring Mountain View and Cupertino.
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.
Sunnyvale Two-ADU FAQ
Can I build two detached ADUs in Sunnyvale?
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. Until then, the city’s code allows one conversion ADU, one new-construction ADU and one JADU.
How large can each ADU be in Sunnyvale?
New construction can be 150 to 1,000 sq ft today, and streamlined units up to 800 sq ft. 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 Sunnyvale?
16 ft, or 18 ft within a half mile of transit, plus 2 ft for roof pitch. Two-story units have window and balcony limits.
How long does ADU review take in Sunnyvale?
The city’s handout says typical review is 2 to 4 weeks. By code, completeness is checked within 15 business days and a decision made within 60 days.
Does my Sunnyvale ADU need fire sprinklers?
Only if the main house is sprinklered, or if a detached unit is more than 150 ft of hose reach from fire access.
Who builds two-ADU projects in Sunnyvale?
Axiom Renovation designs, permits and builds ADUs in Sunnyvale 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.