Accessory Dwelling Units (ADUs)

ADUWhat is an ADU?

Commonly known as a second unit, granny flat, or in-law unit, an Accessory Dwelling Unit (ADU) is defined as "an attached or a detached residential dwelling unit which provides complete independent living facilities for one or more persons." By definition, an ADU includes permanent provisions for living, sleeping, eating, cooking, and sanitation.

What is an JADU?

An Junior Accessory Dwelling Unit (JADU) is defined in California Government Code Section 65852.22 as a unit that is no more than 500 square feet in size and contained entirely within a single-family residence. A junior accessory dwelling unit may include separate sanitation facilities, or may share sanitation facilities with the existing structure. 

What does it mean to be "streamlined"?

A streamlined ADU enables a property owner to submit an application without providing an additional parking space. In many cases of non-streamlined ADUs, the additional parking space of 9'x19' can be shown to fit in the existing driveway, or within a three-car garage.

↪ It is important to note that streamlined ADUs may not be used for short term rentals. This includes most detached ADUs below 800 square feet and attached ADUs/JADUs that are comprised of converted existing space. See below for regulations.

↪ Streamlined ADUs are processed ministerially, as are non-streamlined ADUs. There is no difference in the processing time for these two categories, although impact fees will not apply to ADUs below 750 square feet (see Fees below).

Current Regulations 

The current ADU ordinance, effective June 18, 2020, sets the following regulations below for ADUs. ADU's that the meet the standards listed below will be processed as a ministerial building permit and is not subject to any discretionary review. See Orinda Municipal Code Section 17.3.4 for the entire ADU code section.

Streamlined ADUs

  1. Within Existing Space (Single-Family) - ADUs and JADUs
    • The property contains an existing or proposed single-family dwelling.
    • Allowed one ADU and one JADU.
    • The ADU/ JADU has exterior access independent from the existing residence.
    • The existing structure has side and rear setbacks sufficient for fire and safety. If the existing structure complies with the City’s setback requirements, this standard is automatically met.
    • Small (<150 square-feet) addition allowed to accommodate ingress/egress.
    • If a JADU is proposed, it complies with the requirements of Government Code Section 65852.22.
  2. Detached, New Construction (Single-Family) - ADU
    • The property contains an existing or proposed single-family dwelling.
    • The property does not contain another ADU, but may contain an JADU.
    • The ADU is detached from the single-family dwelling.
    • The ADU is new construction.
    • The ADU maintains a minimum 4’ side and rear yard setback, is under 800 square-feet in size, and does not exceed 16’ in height.
  3. Within Existing Space (Multifamily) - ADUs
    • The property contains an existing multifamily dwelling.
    • The ADU is located within a portion of the multifamily dwelling structure that is not used as livable space.
    • The total number of ADUs within the dwelling structure does not exceed 25% of the existing number of primary dwelling units within the structure, provided that all multifamily dwelling structures are permitted to have one ADU.
  4. Detached, New Construction (Multifamily) - ADU
    • The property contains an existing multifamily dwelling.
    • The ADU is detached from the multifamily dwelling.
    • The ADU maintains a minimum 4’ side and rear yard setback and does not exceed 16’ in height.
    • No more than 2 ADUs per lot.

All Streamlined ADUs

  • Parking: No parking space required.
  • Short-term Rental: No short-term rental allowed in streamlined ADUs.

Standard ADUs

All other ADUs that do not meet the standards for streamlined ADUs shall meet the following development standards:

  • Passageways: To the extent required by California Government Code Section 65852.2, no passageway is required in conjunction with construction of an ADU.
  • Setbacks: 
    • No setback required for an ADU located within existing living area or an existing accessory structure, or an ADU that replaces an existing structure and is located in the same location and to the same dimensions as the structure being replaced.
    • All other ADUs - Minimum 4’ side and rear yard setback.
  • Height: 
    • Attached ADU - In the area between the setback applicable to the primary dwelling and the setbacks applicable to the ADU, the ADU is limited to a maximum 16’ height. Otherwise, the height limits applicable to the primary dwelling apply.
    • Detached ADU - Maximum 16’ height. Detached ADUs located wholly or partially above a garage is limited to 16’ in height in the area between the setbacks applicable to the primary dwelling the setbacks applicable to the ADU and otherwise the height limits applicable to the primary dwelling apply.
  • Size: Maximum of 850 square-feet for a studio or one-bedroom. Maximum of 1,000 square-feet for more than one bedroom.  
  • Parking: Required 1 parking space per ADU, except for units located within 1/2 mile walking distance from transit, that are part of a new single-family residence, or meet other state-specified conditions. No replacement parking required when an existing garage is converted into an ADU. The required parking space may be provided as a tandem space is an existing driveway or in the required setbacks.


No impact fees are assessed for ADUs smaller than 750 square-feet. Impact fees for ADUs 750 square-feet and larger are assessed proportionally in relation to the square-footage of the primary dwelling unit. Plan check fees are due for all ADUs.

↪ Estimate your impact fees here.

ADU applications that meet the regulations listed above shall be submitted as a building permit application. See the Building Permits page for more detail on obtaining a building permit for an ADU. 

Frequently Asked Questions

  • Where are ADUs allowed in Orinda? An ADU may be constructed on any property zoned for residential use. 
  • How many ADUs can I build on my property? Properties zoned for single-family use are permitted one ADU and one JADU.
  • Can my ADU be prefabricated/modular/manufactured construction? Yes, the zoning code does not limit the type of construction. Please contact the Building Department for building code requirements pertaining to manufactured homes.
  • Is my ADU required to have fire sprinklers? The ADU is not required to have fire sprinklers if fire sprinklers are not required for the primary dwelling.
  • Can my ADU have a separate address? Yes, please contact the Moraga-Orinda Fire District for a new address assignment. 
  • Do I have to construct a new garage/carport if I convert my existing one into an ADU? No, when a private garage, carport, or covered parking structure is demolished or converted in conjunction with an ADU, the parking spaces do not need to be replaced.
  • What if I want to build an ADU combined with another project on my property? For combination proposals, applicants can elect to have the ADU processed independent of the other proposal(s) or as a combined review. If the applicant decides on a combined review, they are voluntarily foregoing the ADU streamlining deadlines. 
  • What if I want to build an ADU that does not meet one or more of the requirements? Approval of an Variance is required for a ADU that does not meet the regulations. One example would be not meeting setback requirements.
  • My neighbor is building an ADU. Why wasn’t I notified? If an ADU meets the regulations listed above, the application is processed ministerially and there is no neighbor notification requirement.

Still have questions?

Fill out the below form to request more information. You can also schedule a 30-minute appointment to discuss your questions with the Planning Department here.