Two Detached ADUs in Campbell (AB 956, 2027)
Plan Two ADUs in Campbell: Free Site Assessment
Campbell ADU rules today (2026)
From January 1, 2027, state law (AB 956) requires cities, including Campbell, to approve up to two detached ADUs on a lot with a single-family home. Campbell updated its ADU rules in 2025 with an urgency ordinance that already exempts many 800 sq ft units from lot coverage and floor area limits. Here is how the new law and the current local ADU rules fit together.
- Units allowed now: the city’s ADU code (Municipal Code Ch. 21.23) allows one standard ADU, one statewide-exemption ADU and one JADU on a single-family lot.
- Detached ADU size: up to 1,200 sq ft. An attached ADU can be 50% of the main home, with at least 1,000 sq ft allowed (Ord. No. 2322, February 18, 2025).
- Height: 20 ft for a detached ADU under Ord. 2322.
- 800 sq ft units: an ADU of 800 sq ft or less with 4 ft side and rear setbacks is exempt from lot coverage, floor area ratio, open space and building separation rules, and may go in the front setback if no other location works.
- Setbacks: the city’s ADU code allows 4 ft side and rear setbacks for detached ADUs.
- Parking: no parking may be required, including no replacement parking.
- Process: ministerial review under state law, with a 60-day decision clock. Ord. 2322 was adopted as an interim urgency measure, so we confirm with Campbell Planning which version is in effect.
State review of Campbell's ADU rules
On June 30, 2023, HCD sent Campbell findings on its ADU ordinance (Ord. 2291). HCD listed 16 issues. Among them: the city must allow the converted, detached and JADU combination of three units; side and rear setbacks can be no more than 4 ft; a 10 ft building separation cannot apply to statewide-exemption units; floor area and coverage rules cannot block an 800 sq ft ADU; and a sprinkler requirement tied to the main home had to be removed. 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 Campbell to approve up to two detached, new-construction ADUs on a lot with a single-family home. Each of the two may be limited to 800 sq ft of living space, local height limits can still apply, and side and rear setbacks can be no more than 4 ft. Where two detached ADUs are built, a JADU on the same lot does not have to be approved. Owners in HOAs also gain protections.
Campbell already allows a standard ADU plus a statewide-exemption ADU, but the second detached unit is tied to the state 800 sq ft route. AB 956 makes two detached new-construction units the rule. Because Campbell already exempts 800 sq ft units with 4 ft setbacks from coverage and separation limits, two such units fit many lots. Campbell will need to update its ordinance, and we confirm current rules as it does.
Planning two detached ADUs on a Campbell lot
- Trees: Campbell’s tree protection rules do not apply where a protected tree’s root zone falls inside the footprint of a statewide-exemption ADU. Otherwise tree protection still applies.
- Sprinklers: the city’s ADU code does not require sprinklers in an ADU if they are not required in the main home.
- Separation: larger ADUs follow the main-structure separation standard, while 800 sq ft units with 4 ft setbacks are exempt.
- Electrical: two units plus the main home usually need a load calculation and often a service upgrade.
Building ADUs in Campbell with Axiom
Axiom Renovation designs, permits and builds ADUs in Campbell. Read our Campbell ADU guide, see our Campbell service area, or start with the AB 956 overview. Neighbors can read the guides for Los Gatos and San Jose.
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.
Campbell Two-ADU FAQ
Can I build two detached ADUs in Campbell?
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. Today Campbell allows a standard ADU, a statewide-exemption ADU and a JADU.
How large can each ADU be in Campbell?
Campbell currently allows a detached ADU of up to 1,200 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 Campbell?
Campbell’s 2025 ordinance sets a 20 ft height limit for detached ADUs. We confirm the current limit with the city for each project.
Does an 800 sq ft ADU count toward lot coverage in Campbell?
No. An ADU of 800 sq ft or less with 4 ft side and rear setbacks is exempt from lot coverage, floor area ratio, open space and building separation limits.
Will a tree stop my ADU in Campbell?
Not always. Campbell’s tree protection rules do not apply where a protected tree’s root zone falls inside the footprint of a statewide-exemption ADU, but they do apply in other cases.
Who builds two-ADU projects in Campbell?
Axiom Renovation designs, permits and builds ADUs in Campbell 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.