Understanding Accessory Dwelling Units (ADUs)

Did You Know?

Government Code 65852.150:

The Legislature finds and declares all of the following:

1. Accessory dwelling units are a valuable form of housing in California.

2. Accessory dwelling units provide housing for family members, students, the elderly, in-home health care providers, the disabled, and others, at below-market prices within existing neighborhoods.

3. Homeowners who create accessory dwelling units benefit from added income, and an increased sense of security.

4. Allowing accessory dwelling units in single-family or multifamily residential zones provides additional rental housing stock in California.

5. California faces a severe housing crisis.

6. The state is falling far short of meeting current and future housing demand with serious consequences for the state’s economy, our ability to build green infill consistent with state greenhouse gas reduction goals, and the well-being of our citizens, particularly lower and middle-income earners.

7. Accessory dwelling units offer lower-cost housing to meet the needs of existing and future residents within existing neighborhoods while respecting architectural character.

8. Accessory dwelling units are, therefore, an essential component of California’s housing supply.

What is an ADU?

An ADU is an accessory dwelling unit with complete independent living facilities for one or more persons and has a few variations:

• Detached: The unit is separated from the primary structure.

• Attached: The unit is attached to the primary structure.

• Converted Existing Space: Space (e.g., master bedroom, attached garage, storage area, or similar use, or an accessory structure) on the lot of the primary residence that is converted into an independent living unit.

• Junior Accessory Dwelling Unit (JADU): A specific type of conversion of existing space that is contained entirely within an existing or proposed single-family residence.

ADUs tend to be significantly less expensive to build and offer benefits that address common development barriers such as affordability and environmental quality. Because ADUs must be built on lots with existing or proposed housing, they do not require paying for new land, dedicated parking, or other costly infrastructure required to build a new single-family home. Because they are contained inside existing single-family homes, JADUs require relatively modest renovations and are much more affordable to complete. ADUs are often built with cost-effective one or two-story wood frames, which are also cheaper than other new homes. ADUs can provide as much living space as apartments and condominiums and work well for couples, small families, friends, young people, and seniors. ADUs also give homeowners the flexibility to share independent living areas with family members and others, allowing seniors to age in place as they require more care, thus helping extended families stay together while maintaining privacy.