Accessory Dwelling Units (ADUs)

What are ADUs?

photo of house

Accessory Dwelling Units (ADUs) are known by many names: granny flats, in-law units, backyard cottages, secondary units and more. No matter what you call them, ADUs are an innovative, affordable, effective option for adding much-needed housing in California.

What are the benefits of ADUs?

New laws effective January 1, 2018

Recent state legislation provides clarification and fee assistance for the creation of ADUs. Governor Brown signed two separate bills on October 8, 2017: SB 229 (Wieckowski) and AB 494 (Bloom).

These bills, effective January 1, 2018, clarify and improve various provisions of the law to promote the development of ADUs, including allowing ADUs to be built concurrently with a single-family home, opening areas where ADUs can be built to include all zoning districts that allow single-family uses, modifying fees from utilities, such as special districts and water corporations, and reducing parking requirements. Please see the HCD Technical Assistance Memorandum: Accessory Dwelling Unit Legislation (SB 229 & AB 494) (PDF), dated May 29, 2018, for further information.

Recent updates to state laws for ADUs

State legislation that took effect January 1, 2017 gave California cities more flexibility and latitude for allowing homeowners to build ADUs. Three separate bills were introduced and signed by Governor Brown; SB 1069 (Wieckowski), AB 2299 (Bloom), and AB 2406 (Thurmond). Each of these land use bills make it easier than ever for homeowners to take advantage of this attractive opportunity.

Webinar : Recent Legislation "Nuts and Bolts"


Technical Assistance Booklet

Download entire booklet (PDF)

Information for cities, counties, other local government bodies, and homeowners interested in adding an accessory dwelling unit to their property.

Download the entire booklet (PDF) or select one of the following excerpts:

New!  Updated ADU booklet coming soon!


City and county ADU ordinances and HCD review letters

Cities and counties are not required to create ordinances for ADUs; however, any city/county that does adopt an ADU ordinance, must submit the ordinance to HCD within 60 days.

Sample materials from cities and counties

Additional guidance

External websites

You'll find additional resources at the following websites, which are hosted by partners who contributed to HCD's Technical Assistance Booklet.