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Accessory Dwelling Units (“ADU”) have been known by many names over the years: granny flats, second units, in-law units, backyard cottages, and more. ADUs are an innovative, affordable, and effective option for adding much-needed housing in California.

ADUs provide independent living quarters for one household on the same lot as the primary single-family dwelling. The ADU provides full facilities for sleeping, eating, cooking, and sanitation. The ADU may be detached, attached, or a converted structure located within the living areas of the primary dwelling unit on the lot.

  • Detached: the ADU structure is detached from the primary dwelling unit.
  • Attached: the ADU structure is attached to the primary dwelling unit.
  • Converted: the ADU within the existing primary dwelling unit or the ADU was established through the conversion of an accessory structure, for example, a garage or pool house.
  • Junior ADU: the ADU is within the existing walls of the single-family residence, and there is a size limit of 500 square-feet.
ADU Types

Knowing what type of ADU you want to build is important because there are different requirements and development standards for the various types of ADUs and these standards vary from city to city. Here are some links to city websites that have more  ADU information specific to the city. 

Click the City Links below To Learn More: 


In the past couple years there have been grant programs through the California Department of Housing and Community Development to help build ADUs but tas of the writing of this, that program has ended. There may be others in the future so keep checking. Read more about the requirements in your city buy searching the city's ordinances. If your city has none, then your city uses current California state law.

California Department of Housing and Community Development ADU Handbook

SB 477 added a new Chapter 13 to Division 1 of Title 7 of the Government Code. The new Chapter 13 is divided into four articles, and each article is further divided into various sections as follows:

Article 1 – General Provisions. Now provided in Gov. Code sections 66310, 66311, 66312, and 66313. 
Article 2 – ADU Approvals. Now provided in Gov. Code sections 66314 through 66332.
Article 3 – Junior ADUs. Now provided in Gov. Code sections 66333 through 66339.
Article 4 – ADU Sales. Now provided in Gov. Code sections 66341 and 66342.