Governor Newsom Signs Four New Accessory Dwelling Unit Bills

Few legislative changes in California have become more predictable than the Legislature’s annual revisions to the laws governing accessory dwelling units (ADUs) and junior accessory dwelling units (JADUs). Recent examples of past legislation include requiring ministerial approval of applications within 60 days, allowing ADUs to be sold separately from the primary dwelling in certain situations, allowing property owners to legalize unpermitted ADUs and JADUs (with limited exceptions), and increasing the quantity of detached ADUs that can be built on a lot with an existing multifamily dwelling. (For more information, see prior BBK ADU legal alerts covering SB 477, AB 345, AB 2533, and SB 1211).

2025 was no different, with Governor Newsom signing four more ADU bills into law last month: AB 462, AB 1154, SB 9, and SB 543. AB 462 was enacted as an urgency measure and took immediate effect when signed on October 10, 2025. AB 1154, SB 9, and SB 543 were enacted on the same day but as non-urgency measures, so they take effect on January 1, 2026. These latest changes are wide-ranging, but largely technical and clarifying in nature. Nonetheless, local ordinances must be updated as soon as possible to avoid becoming null and void in their entirety because of nonconformities with state law.

Noteworthy features from each bill are summarized below.

AB 462 – Coastal Development Permits; Disaster-Affected Areas

Existing law requires certain ADUs proposed in coastal areas to obtain a coastal development permit (CDP) in addition to other local ADU-permit requirements. Historically, the CDP for an ADU was not subject to state ADU law’s 60-day shot clock to approve or deny a complete ADU application. Additionally, local permitting decisions on a CDP for an ADU could be appealed to the California Coastal Commission if the underlying property was subject to the Coastal Commission’s appeals jurisdiction (as set forth in Pub. Resources Code, § 30603).

AB 462 alters the CDP status quo on numerous fronts. Most notably, local agencies with a certified local coastal program (LCP) must now approve or deny a completed CDP application for an ADU within 60 days. AB 462 also eliminates the ability to appeal a CDP for an ADU to the Coastal Commission. (Gov. Code, § 66329(c), as amended.) If a local agency does not have a certified LCP, then it must “immediately notify” the Coastal Commission when an ADU application is submitted. And subject to limited exceptions, the Coastal Commission’s review of the CDP application is also subject to a 60-day shot clock. (Id., at (b)(1)–(5).)

Beyond the CDP changes, AB 462 relaxes the rules governing the issuance of a certificate of occupancy (CofO) for an ADU in disaster-affected areas. Historically, state law prohibited a local agency from issuing a CofO for an ADU before one was issued for the primary dwelling. AB 462 creates a narrow exception for detached ADUs when all of the following conditions are satisfied: (1) the Governor has declared a state of emergency for the county on or after February 1, 2025; (2) the primary dwelling was substantially damaged or destroyed by an event referenced in the state of emergency proclamation; and (3) the ADU has been issued construction permits and passed all required inspections. (Gov. Code, § 66328(b), as amended.) If these conditions are satisfied, a detached ADU can now receive a CofO before the primary dwelling. In all other scenarios, the existing prohibition continues to apply.

AB 1154 – JADU Owner-Occupancy; Short-Term Rental

Existing state law requires a property owner to reside in the JADU or the remaining portion of the single-family structure. 

AB 1154 narrows this requirement to now only apply when the JADU shares sanitation facilities (bathroom) with the single-family dwelling. If the JADU has its own bathroom, then the property owner does not have to reside on the property. (Gov. Code, § 66333(b), as amended.)

This bill also prohibits JADUs from being used as short-term rentals (i.e., less than 30 days). Now, every JADU, ADU approved under Government Code section 66323, and (if the local agency so chooses) ADU created under Government Code section 66314 through 66322 must be rented for a term longer than 30 days. (See amended Gov. Code, § 66333(g); existing Gov. Code, §§ 66315, 66323(e).)

SB 9; SB 543 – Ordinance Submittal to HCD; Approval

Under existing law, local agencies must submit a copy of their ADU ordinance to the California Department of Housing and Community Development (HCD) within 60 days of adoption. 

This year’s SB 9 and SB 543 add a penalty for failing to do so by rendering null and void any local ADU ordinance that is not submitted to HCD within 60 days of adoption. (Gov. Code, § 66326(d), as amended; new Gov. Code, § 66333.5(d).) The bills further specify that a local ADU ordinance is null and void if HCD issues findings that the ordinance does not comply with state law and the local agency fails to respond to HCD within 30 days. (Ibid.) Collectively, these changes highlight the importance of timely submitting an ADU ordinance to HCD and responding to any adverse findings.

SB 543 – ADU Size; Number of ADUs; Impact Fees; Permitting Timeline

SB 543 makes numerous changes and clarifications to state ADU law, the most notable of which are summarized below. 

ADU & JADU Size

Existing law limits the maximum size of a JADU to 500 square feet and prohibits local ADU ordinances from imposing certain development standards that would prevent an ADU created under Government Code sections 66314 through 66322 from being at least 800 square feet.

SB 543 amends state law to specify that statutory references to the allowable square footage of an ADU or JADU refer to square footage of “interior livable space.” (Gov. Code, §§ 66313(d); 66321(b)(2), as amended.)

Impact Fees

Existing law exempts ADUs that are 750 square feet or smaller from development impact fees (DIFs).

SB 543 clarifies that DIFs may not be imposed on an ADU that has 750 or fewer square feet of interior livable space or on a JADU with 500 or fewer square feet of interior livable space. The bill also exempts an ADU or JADU with 500 or fewer square feet of interior livable space from school impact fees. (Gov. Code, § 66311.5, as amended.)

Quantity of ADUs Created Under Government Code section 66323

Existing state law creates four categories of ADUs that must be approved by a building permit only if they comply with the standards provided in Government Code section 66323(a)(1)–(4). These are:

1. A converted ADU and a JADU created on a lot with a proposed or existing single-family dwelling (Gov. Code, § 66323(a)(1));
2. A detached ADU created on a lot with a proposed or existing single-family dwelling (Gov. Code, § 66323(a)(2));
3. A converted ADU or ADUs in an existing multifamily dwelling (Gov. Code, § 66323(a)(3)); and 
4. Detached ADUs on a lot with a proposed or existing multifamily dwelling (Gov. Code, § 66323(a)(4).) 

For some time, there has been uncertainty as to whether ADUs created under Government Code section 66323 could be combined (e.g., if a lot with a single-family dwelling could have a detached ADU, a converted ADU, and a JADU). SB 543 resolves that uncertainty in the affirmative: Combinations are permitted. Consequently, a lot with a multifamily dwelling can combine converted ADUs and detached ADUs (created under section 66323 (a)(3) and (a)(4), respectively). And a lot with a single-family dwelling can combine a converted ADU and a JADU with a detached ADU (created under section 66323(a)(1) and (a)(2), respectively). (Gov. Code, § 66323(a), as amended.) 

ADU Permitting Process

Existing law has long required local agencies to approve or deny an ADU application within 60 days of receiving a complete application. State law was silent, however, with respect to application-incompleteness determinations, subsequent resubmittals, and appealing local decisions on ADU applications. 

SB 543 requires local agencies to: 

1. Determine whether an ADU application is complete within 15 business days of submittal; 
2. If the application is incomplete, within the same 15 days, provide the applicant with a list of incomplete items and an explanation on how to address them; 
3. Review a resubmitted application for completeness within 15 business days; 
4. Provide the applicant with a “written appeal” process for any incompleteness determination or denial (to the Planning Commission or City Council, or both); and 
5. Provide a final written determination on the appeal within 60 business days of receiving the appeal. (Gov. Code, §§ 66317 [ADUs], 66335 [JADUs]; as amended.) 

To further understand these changes and their implications for cities and how they must process ADU and JADU applications, consult your BBK attorney or the authors of this legal alert.

Disclaimer: BBK Legal Alerts are not intended as legal advice. Additional facts, facts specific to your situation, or future developments may affect subjects contained herein. Seek the advice of an attorney before acting or relying upon any information herein.