Two Detached ADUs in Orinda (AB 956, 2027)
Plan Two ADUs in Orinda: Free Site Assessment
Orinda ADU rules today (2026)
From January 1, 2027, state law (AB 956) requires the City of Orinda to approve up to two detached ADUs on a lot with a single-family home. Orinda’s hillside lots and fire hazard zones make site planning the first step, and the draft Lamorinda pre-approved plans give owners a set of units already sized under 800 sq ft.
- Code: Orinda Municipal Code § 17.3.4, last amended by Ordinance No. 25-02 (May 20, 2025), as published in code libraries.
- Units allowed now: the city’s ADU code allows one ADU plus one JADU on a single-family lot under streamlined rules, or one ADU under general standards.
- Size: up to 850 sq ft for a studio or one bedroom and 1,000 sq ft for two or more. A streamlined detached new-construction ADU is 800 sq ft or less.
- Height: 16 ft for a detached ADU, 18 ft near transit (plus 2 ft for roof pitch).
- Setbacks: 4 ft side and rear; none for existing structures or same-footprint rebuilds.
- Parking: one space (tandem allowed) for an ADU with a bedroom, exempt within half a mile of BART or a bus stop.
- Process: ministerial approval by the Planning Director within 60 days of a complete application. Contra Costa County issues the building permit.
- Pre-approved plans: the county Pre-Approved ADU program, with an Orinda-specific checklist, and the draft Lamorinda prototypes of 495 to 796 sq ft.
What changes on January 1, 2027
AB 956 raises the number of detached, new-construction ADUs the city must approve from one to two. 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 are built, the city need not approve a JADU. HOA protections also apply.
Orinda’s code allows one ADU plus a JADU today, so a second detached unit is new. Its streamlined detached ADU (800 sq ft, 16 ft, 4 ft setbacks) already matches the AB 956 size, and all four draft Lamorinda prototypes are under 800 sq ft. Orinda will need to update its ordinance, and we confirm current rules with the city as it does.
Recent Axiom work
Professional photos from a recent Axiom Renovation full remodel and addition in Los Gatos.
Planning two detached ADUs on an Orinda lot
- Fire: 2025 state maps give Orinda the largest Very High fire hazard area in Contra Costa County. Moraga-Orinda Fire District defensible-space zones apply: Zone 0 (0 to 5 ft), Zone 1 (5 to 30 ft) and Zone 2 (30 to 100 ft). An ADU needs sprinklers only if the main home requires them.
- Slopes: the county’s Orinda pre-approved ADU checklist requires a geotechnical report when the slope is over 5% or there is 1 ft of grade change across the ADU.
- Close placement: the same checklist requires a 1-hour rated wall and eave detail when an ADU is under 5 ft from a property line or under 10 ft from another building. That matters when two units share a backyard.
- Septic: some Orinda lots are on septic and need a percolation test from the last five years (ten if recertified). Central San serves the rest of the city for sewer.
- Utilities: two units usually need a load calculation and often an electrical service upgrade, plus sign-off from your water provider.
Building ADUs in Orinda 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 Orinda ADU builder page, our Orinda service area page, the AB 956 overview, and guides for nearby Moraga and Lafayette.
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.
Orinda Two-ADU FAQ
Can I build two detached ADUs in Orinda?
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 Orinda’s code allows one ADU plus a JADU.
How large can each ADU be in Orinda?
Today Orinda’s code allows up to 850 sq ft for a studio or one bedroom and 1,000 sq ft for two or more. 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 Orinda?
16 ft, or 18 ft near transit with 2 more feet allowed for roof pitch.
How long does ADU approval take in Orinda?
The Planning Director approves ADUs ministerially within 60 days of a complete application. Contra Costa County then issues the building permit.
Do I need a geotechnical report for an ADU in Orinda?
For a county pre-approved ADU, yes when the slope is over 5% or there is 1 ft of grade change across the unit.
Who builds two-ADU projects in Orinda?
Axiom Renovation designs, permits and builds ADUs in Orinda 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.