California accessory dwelling unit (ADU) laws have undergone significant changes, creating new opportunities for homeowners, developers, and investors. Recent legislative updates have boosted ADU popularity; understanding California ADU laws allows stakeholders to benefit from the state’s evolving housing landscape.
Overview of California ADU laws
An accessory dwelling unit is a second residence that can be built on the same lot as the primary residence. In California, ADUs have been gaining in popularity as the demand for housing in the state continues to grow. ADUs can provide additional housing units in existing residential neighborhoods, which can help address the housing shortage in California. Homeowners, developers, and investors can benefit from ADUs in a number of ways, including (1) increasing property value by adding additional living space to the property, (2) allowing for multigenerational living where families live together but maintain their independence, and (3) providing rental income by renting either the ADU or the main residence, or both.
The legal framework for ADUs in California continues to evolve. A number of new laws took effect in 2024 to encourage their development, and the legislature has continued passing significant ADU legislation nearly every year since, with more laws taking effect in 2025 and 2026. The California Department of Housing and Community Development (HCD) maintains an ADU Handbook and serves as the state’s lead authority on local ADU ordinances.
Key considerations of California’s new ADU laws
AB1033: Separate Sale of ADUs. Assembly Bill 1033 (AB 1033) is a significant first step in allowing for the sale of ADUs in California because it removes the state-level restriction on selling ADUs. Previously, an ADU could only be sold separately from the main residence in very limited circumstances, such as if it was developed by a qualified nonprofit. AB 1033 creates the legal framework that authorizes local governments to allow for the separate sale of any ADUs as condominium units, as set forth in Section 66342 of the California Government Code.
San Jose was the first city to implement AB 1033, adopting its own ordinance in June 2024. Since then, a small but growing number of jurisdictions have followed suit, including Santa Monica, the City of San Diego, unincorporated San Diego County, the City of Santa Cruz, Berkeley, San Pablo, Sebastopol, and San Francisco.
For Homeowners Associations (HOAs), new ADUs in existing associations must comply with HOA governing documents, the Davis-Stirling Act, and the Subdivision Map Act. Lien holder consent is required, and HOAs must approve the creation of condos if local ordinances are met. Local agencies must notify ADU applicants of these requirements.
This is an area that homeowners, HOAs, developers, and investors interested in ADUs should continue to watch, as there will be the opportunity to sell ADUs once other cities implement AB 1033.
AB 976: No Owner-Occupancy Requirements. Property owners may continue to build rental ADUs in California because Assembly Bill 976 (AB 976) permanently extended the rental unit provisions set to expire in 2025. Previously Assembly Bill 881, which was passed in 2020, prohibited local governments from imposing owner-occupancy requirements on properties where ADUs are built until 2025. The new AB 976 removes the sunset provision and permanently allows owners to build rental ADUs on their properties, which promotes the construction of additional rental housing in California.
AB 1332: Pre-Approved ADU Plans. As of January 1, 2025, all cities and municipalities in California were required to have a program in place for the preapproval of ADU plans, pursuant to Assembly Bill 1332 (AB 1332). Preapproved ADU plans are posted on each local agency’s website, and the local agency must approve or deny an application within thirty (30) days from the date it receives a completed application for an ADU containing preapproved plans. Senate Bill 543 (SB 543), effective January 1, 2026, layered additional, more prescriptive timelines onto this process, including a 15-business-day initial completeness review for ADU and junior accessory dwelling unit (JADU) applications generally. A JADU is a smaller unit of up to 500 square feet, carved out of existing single-family home space. The pace of ADU legislation shows no signs of slowing. Governor Newsom signed three ADU bills in 2024 and four more in 2025, Nixon Peabody will continue to monitor how SB 543 and other 2026 ADU laws are implemented at the local level.
Additional ADU laws effective in 2025 and 2026
Beyond the 2024 laws described above, the California Legislature has continued to pass significant ADU legislation. Key additions include:
- AB 2533: Legalizing pre-2020 unpermitted ADUs. Effective January 1, 2025, AB 2533 generally prohibits local agencies from denying a permit to legalize an existing ADU or JADU built before January 1, 2020, based solely on building standard violations, unless the violation presents a genuine health or safety risk.
- SB 1211: More ADUs on multifamily properties. Effective January 1, 2025, SB 1211 increases the number of detached ADUs allowed on a lot with an existing multifamily dwelling from two to eight, provided the number of new ADUs does not exceed the number of existing units, and removes certain parking-replacement requirements.
- SB 543: Standardized permitting timelines. Effective January 1, 2026, SB 543 codifies a 15-business-day initial completeness review for ADU and JADU applications, reinforces the existing 60-day ministerial approval requirement, and clarifies consistent treatment of JADUs alongside ADUs statewide.
The legislature has also continued to pass narrower ADU-related bills nearly every session. For example, AB 462 (2025) allows an ADU to receive a certificate of occupancy before the primary dwelling is rebuilt, where the primary dwelling was destroyed or substantially damaged in a governor-declared state of emergency.
Given the pace of change, homeowners, developers, and investors should consult legal counsel to confirm which provisions apply to their specific project.
Impacts of California’s new ADU laws on homeowners and developers
Homeowners, developers, and investors may now build ADUs for rental housing without any owner-occupancy requirements, as set forth in Section 66315 of the California Government Code. Preapproved ADU plans under AB 1332, together with the additional timelines added by SB 543, help streamline the development of ADUs. And looking forward, as local governments implement AB 1033, homeowners, developers, and investors will also be able to turn ADUs into condominiums and sell them separately from the main residence. Owners of unpermitted pre-2020 ADUs now have a clearer path to legalization under AB 2533, and owners of qualifying multifamily properties can pursue significantly more ADUs under SB 1211.
Navigating local regulations and legal considerations
The State of California is encouraging the development of ADUs, though most implementation happens at the local level. So, it is necessary to understand the local ADU rules for the particular cities and counties where the project is located. As always, working with knowledgeable professionals (licensed architects and legal experts) is important when navigating the complexities of local regulations for developing projects, whether large multi-family housing complexes or small ADUs.
Conclusion
The legal framework for ADUs in California continues to evolve. The new ADU laws effective in 2024, together with additional laws effective in 2025 and 2026, will help streamline the approval process, allow property owners to develop ADUs for rental properties, and once implemented locally allow for the sale of ADUs. The development of ADUs is a great way to add additional housing to existing residential neighborhoods and address the housing shortage in California. Homeowners, developers, and investors should stay informed about local regulations and obtain professional advice when planning an ADU project, including legal advisors and licensed architects, to help navigate the planning, designing, and permitting process.
Frequently Asked Questions
Can I sell my ADU separately from my main home in California?
In cities that have adopted an implementing ordinance under AB 1033, yes: an ADU can be sold separately as a condominium unit. As of 2026, a small number of California jurisdictions, including San Jose, Santa Monica, and unincorporated San Diego County, among others, have adopted such ordinances, so this option is not yet available statewide.
Can I legalize an unpermitted ADU built before 2020?
In most cases, yes. Under AB 2533, effective January 1, 2025, local agencies generally cannot deny a permit to legalize an existing ADU or JADU built before January 1, 2020, solely because it violates a building standard, unless the violation poses a genuine health or safety risk. Local implementation can vary, and a real estate attorney can help assess whether a specific unpermitted unit qualifies and how to navigate the process.
How many ADUs can I build on a multifamily property in California?
Under SB 1211, effective January 1, 2025, a lot with an existing multifamily dwelling may have up to eight detached ADUs, provided the number of new ADUs does not exceed the number of existing units on the property.