What Are ADUs and What Do They Mean for California?


ADUs are nothing new, if you have ever seen an in-law suite you have seen an ADU. Before zoning laws had restricted their construction ADUs were very popular, and there has been a large uptick in their construction in recent years.1 In 2016 ADUs became legal to build in California with the passing of S.B. 1069 and A.B. 2299, and since then around 60,000 have been permitted.1 This number reflects a 1,421 percent increase in the number of Accessory Dwelling Units in the state between 2016 and 2021.1

These numbers may simply continue to rise with the passing of A.B. 2221, which was recently signed into effect in September of this year. This bill was intended to clarify ADU laws and make it easier for homeowners to acquire permits.2 Originally ADUs could only be built as an addition to existing multi-family homes, but not pre-existing ones. Because of this developers had to complete the construction of homes before they could receive permits to construct ADUs on their property. With the passing of this new bill, developers would be able to build ADUs alongside new multi-family homes, as well as reduce the amount of pushback against their construction and ensure that permitting agencies respond to these proposals within 60 days.2

These Accessory Dwelling Units are not only convenient, they are also affordable. Of course, many ADUs are used to house family members of those living in the primary homes, but many are rented instead.1 When looking at the costs of ADU rentals, some of the most expensive areas in the state have ADUs with rental costs of around two thousand dollars. Specifically, Accessory Dwelling Units in Los Angeles County have rental costs of anywhere from 550 to 2,348 dollars.3 The construction of ADUs may be the breakthrough the state is looking for when it comes to addressing homelessness and achieving Regional Housing Needs Allocation(RNHA) requirements.

Although we do not currently have data on these residential spaces, CIRB is looking forward to providing this information in our database next year.

Molly Mellon // CIRB Journalism Intern


1 See Gray, “The Housing Revolution Is Coming”

2 See California YIMBY, “AB 2221”

3 See SCAG, “SCAG Regional Accessory Dwelling Unit Affordability Analysis”