ADU Builder in Orinda, CA
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Why an Orinda ADU Is a Hillside Project
Orinda lots are bigger than most in the Bay Area, but they are steep, wooded and inside a wildfire district. A backyard ADU here usually means planning around slope, oaks, drainage, fire-resistant construction and sometimes a septic system. Axiom Renovation (CA Lic. #1105006) designs, permits and builds detached ADUs, attached ADUs, garage conversions and junior ADUs across Lamorinda.
Our ADU Work
What Orinda Allows
- One ADU plus one junior ADU on a single-family lot. A detached new-construction ADU is allowed.
- Junior ADU: up to 500 sq ft inside the home.
- Standard ADU: up to 850 sq ft for a studio or one bedroom, 1,000 sq ft for more than one bedroom. A streamlined detached ADU is under 800 sq ft.
- 4-foot side and rear setbacks, and generally 16 feet of height for a detached ADU.
- Conversions need no added setback and may add up to 150 sq ft for entry or exit.
- No replacement parking for garage conversions. Streamlined ADUs need no parking; standard ADUs generally need one space, with exemptions such as being within half a mile of transit.
- Ministerial review with no neighbor notice, and a decision within 60 days of a complete application. Impact fees do not apply under 750 sq ft.
The Orinda ADU Permit Path
Orinda City Hall, Planning Department
22 Orinda Way, Orinda, CA 94563 · (925) 253-4200
Planning applications and building permit authorizations are filed online through the City’s Cloudpermit portal.
- Zoning check at City Hall. Orinda Planning confirms setbacks, height, floor area, and whether your project needs design review.
- City planning review in Cloudpermit. Orinda reviews the project before the County will issue anything. ADUs are reviewed ministerially, so there is no design review hearing for a compliant ADU.
- Fire district review by the Moraga-Orinda Fire District (MOFD) where the project requires it.
- County plan check through ePermits, with the City-approved plans.
- County inspections through construction, then final sign-off.
Contra Costa County Department of Conservation and Development
30 Muir Road, Martinez, CA 94553 · Permit Center (925) 655-2700
Submittals are digital through the County ePermits Center. The County’s Lamorinda field office closed in March 2023. Inspections are requested through ePermits or the County inspection line, (925) 646-4108.
Site Questions We Answer First
- Wildfire: The Moraga-Orinda Fire District treats its whole district as a Wildland-Urban Interface community, so new construction must meet California’s wildfire building standards, now the California Wildland-Urban Interface Code that replaced CBC Chapter 7A in the 2025 code cycle.
- Slope and soils: hillside pads often need a soils report, engineered foundation and drainage plan.
- Oaks: listed native oaks 12 inches or more in diameter are protected on developed lots, which can decide where the ADU sits.
- Sewer or septic: EBMUD supplies water, but some Orinda parcels are on septic rather than sewer, which affects the new bathroom.
- Sprinklers: an ADU needs fire sprinklers only if the main house is required to have them.
- Creeks: work inside a creek setback needs an exception permit.
Keep Exploring
More Axiom services in Orinda: Bathroom Remodeling · Kitchen Remodeling · Home Additions · New Home Construction · Orinda overview
Nearby: Lafayette · Moraga · Walnut Creek · All service areas
Read how to build an ADU in your backyard and see our Los Altos ADU project.
Orinda ADU FAQ
Who approves an ADU in Orinda?
The City of Orinda Planning Department reviews the ADU first through its Cloudpermit portal. Contra Costa County then issues the building permit and inspects the work.
Can I build an ADU on a sloped Orinda lot?
Usually, yes. Expect a soils report, an engineered foundation and a drainage plan on steeper pads.
Does an Orinda ADU need fire-resistant construction?
Yes. MOFD treats its district as a Wildland-Urban Interface community, so new construction must meet California’s wildfire building standards.
Can I rent out an ADU in Orinda?
Yes. State law does not allow owner-occupancy requirements for ADUs. A junior ADU still requires the owner to live on the property.