Two Detached ADUs in Danville (AB 956, 2027)
Plan Two ADUs in Danville: Free Site Assessment
Danville ADU rules today (2026)
From January 1, 2027, state law (AB 956) requires the Town of Danville to approve up to two detached ADUs on a lot with a single-family home. Danville already allows up to three units on a single-family lot and larger ADUs on lots over 40,000 sq ft, so many lots here have room for a two-unit plan.
- Code: Town ADU Ordinance No. 2021-01 (adopted March 2, 2021), explained in the town’s ADU handout updated November 2025.
- Units allowed now: up to three on a single-family lot: one attached ADU (new or converted), one JADU and one detached ADU of 800 sq ft or less.
- ADU size: up to 1,200 sq ft on lots under 40,000 sq ft and up to 2,000 sq ft on larger lots. An 800 sq ft ADU is always allowed. JADUs are up to 500 sq ft.
- Height: 16 ft for a detached ADU with reduced setbacks, or 24 ft if it meets the main-house setbacks. Attached ADUs: 25 ft.
- Setbacks: 4 ft side and rear. A survey is required if setbacks are under 5 ft.
- Parking: one space unless exempt, for example within half a mile of transit.
- Process: ministerial staff review. Permit-ready Garden Cottage Program plans get expedited review.
State review of Danville's ADU rules
On April 25, 2023, HCD sent Danville six findings on Ordinance No. 2021-01. They covered ministerial review and the 60-day timeline, front setbacks, JADU combinations and 16 ft heights. The town’s November 2025 handout appears to address the unit combinations. 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 raises the number of detached, new-construction ADUs the town must approve from one to two. The town 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 are built, the town need not approve a JADU. HOA protections also apply.
Danville allows one detached ADU today, and only at 800 sq ft or less when combined with an attached ADU and a JADU. AB 956 makes room for a second detached unit. Because the town may keep height limits, its 24 ft option will matter on larger lots. Danville will need to update its ordinance, and we confirm with the town how the two-unit option combines with its attached-ADU and JADU rules as it does.
Planning two detached ADUs on a Danville lot
- Trees: the town’s tree code protects native oaks and several other species at 10 inches or more in diameter, and any tree of 36 inches or more. Removing one for an ADU requires showing no reasonable design alternative.
- Separation: Danville has no distance rule between buildings, but building code requires 1-hour construction or sprinklers when an ADU is 5 ft or less from another structure. That matters when two units sit close together.
- Slopes: the Engineering Division reviews ADUs on a slope or with grading.
- Fire: San Ramon Valley Fire Protection District. An ADU needs sprinklers only if the main home requires them.
- Utilities: Central San serves Danville for sewer. Two units usually need a load calculation and often an electrical service upgrade, plus sign-off from your water provider.
Building ADUs in Danville with Axiom
Axiom Renovation designs, permits and builds ADUs. For two units we start with a site study of fit, utilities and review path. See our Danville ADU builder page, our Danville service area page, the AB 956 overview, and guides for nearby Alamo and San Ramon.
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.
Danville Two-ADU FAQ
Can I build two detached ADUs in Danville?
From January 1, 2027, AB 956 requires the town to approve up to two detached, new-construction ADUs on a lot with a single-family home, if the project meets objective standards. Today Danville allows one detached ADU along with an attached ADU and a JADU.
How large can each ADU be in Danville?
Today an ADU can be up to 1,200 sq ft on lots under 40,000 sq ft and up to 2,000 sq ft on larger lots. Under AB 956, the town may limit each of two detached ADUs to 800 sq ft of living space.
Can a detached ADU in Danville be taller than 16 ft?
Yes. A detached ADU can be 24 ft high if it meets the setbacks required for the main house. With reduced 4 ft setbacks, the limit is 16 ft.
Is ADU review in Danville discretionary?
No. Danville reviews ADUs ministerially at staff level. Permit-ready Garden Cottage Program plans get expedited review.
Can I remove an oak tree to build an ADU in Danville?
Only if you show there is no reasonable design alternative. Native oaks and several other species of 10 inches or more in diameter are protected, and driplines must be fenced during work.
Who builds two-ADU projects in Danville?
Axiom Renovation designs, permits and builds ADUs in Danville 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 town for every project.