Accessory Dwelling Units (ADUs)


What 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.

Why are ADUs a big deal?

On October 8, 2017, Governor Brown signed two separate bills, SB 229 and AB 494, amending yet again the state statutes pertaining to ADUs. These two bills aim to clarify and improve various provisions of the ADU Statute to further promote the development of ADUs. Unfortunately, the amendments also introduce new ambiguities, and further amendments are expected. Notable changes to the 2018 ADU Statute include:

  1. Expanding areas where ADUs can be built to include all zoning districts that allow single-family uses;
  2. Applying streamlined approval to an ADU proposed to be built concurrently with a single-family dwelling unit;
  3. Allowing zero setback (subject to fire safety) for ADUs that are converts of legally-constructed garages; and
  4. Reducing parking requirements to a maximum of one (1) parking space per ADU*.

How is Orinda dealing with ADUs?

The ADU Statute states that non-compliant municipal ordinances are null and void. Sections of the existing City ordinance were inconsistent with the ADU Statute amendments effective January 1, 2018. Rather than continue to rely on the ADU Statute, the City adopted a new ADU ordinance (18-02) in compliance with State law. Ordinance 18-02 restores some additional local control over ADU applications and provides clarity regarding the standards that apply to the City’s review of such applications. The Ordinance also repeals the City’s existing ADU regulations and incorporates the changes required by State law. 

New Regulations

Similar to the 2017 state regulations, the 2018 changes in state laws contain specific requirements for the City’s review of ADUs. These requirements differ depending on whether a unit creates new square footage. In addition to the state’s ADU classification and to better facilitate review, Ordinance 18-02 categorizes the review of ADUs based on the following:

  1. Category 1: No New Square Footage. 
  2. Category 2: New Square Footage.

For more on the new ADU regulations, please see the February 20, 2018 City Council Staff Report and accompanying attachments here: 2018 ADU Amendments

More Information

For additional information or questions regarding ADUs, please contact Senior Planner, Mayank Patel, via email at or by phone at (925) 253 - 4212.