HCD ADU Handbook 2026 Update

The California Department of Housing and Community Development (HCD) has released an updated edition of its Accessory Dwelling Unit (ADU) Handbook, reflecting recent changes to State ADU Law effective January 1, 2026.

The updated Handbook is your comprehensive guide to understanding ADU and Junior ADU (JADU) regulations in California, and is intended for homeowners, developers, local agencies, advocates, and legal professionals navigating the permitting process.

Access the Updated ADU Handbook here.

Key topics includes the following changes to state ADU law (effective June 30, 2025, October 10, 2025, and January 1, 2026):

AB 1154 (Chapter 507, Statutes of 2025), SB 9 (Chapter 510, Statutes of 2025), SB 543 (Chapter 520, Statutes of 2025), AB 462 (Chapter 491, Statutes of 2025), and AB 130 (Chapter 22, Statutes of 2025) made various changes to State ADU Law.

• Updated and Added Government Code Sections. Government Code sections related to ADU and JADU Law were updated from 66324, 66327, and 66332 to sections 66311.5, 66313.5, and 66311.7, respectively. Additionally, Government Code section 66333.5 was added.  

• JADU Owner Occupancy. Clarified that if a JADU has shared sanitation facilities with the primary structure, owner-occupancy will be required. If the JADU does not have shared sanitation facilities, owner occupancy will not be required (Gov. Code, § 66333, subd. (b)). Additionally, made changes that stipulate JADUs can no longer be used as short-term rentals and, if rented, must now be rented for longer than 30 days (Gov. Code, § 66333, subd. (g)).

• Local Ordinance Requirements. Clarified that if a local agency fails to submit an adopted ADU ordinance to HCD within the 60-day timeline or fails to respond to HCD’s findings regarding its ordinance within the 30-day timeline, that ordinance is null and void and the local agency must only apply State ADU Law when permitting ADUs (Gov. Code, § 66326, subd. (d)). Additionally, section 66333.5 was added, which specifies that if a local agency fails to submit an adopted JADU ordinance to HCD within the 60-day timeline or fails to respond to HCD’s findings regarding their ordinance within the 30-day timeline, that ordinance is null and void and the local agency must only apply State ADU Law when processing applications for JADUs.  

• Application Requirements. Required a permitting agency to determine whether an application for an ADU or JADU is complete and provide written notice of the determination no later than 15 business days after the permitting agency received the application (Gov. Code, § 66317, subd. (a)(2)(A)). If an application is determined to be incomplete, the permitting agency must provide the applicant with a list of incomplete items and a description of how the application can be made complete in the written notice (Gov. Code, § 66317, subd. (a)(2)(B)). If a permit application is determined to be incomplete or is denied, the permitting agency must provide a process for an applicant to appeal the incompleteness determination or denial and the permitting agency must provide a final written determination no later than 60 business days after receipt of the written appeal (Gov. Code, § 66317, subd. (d)(1)).

• Applications in the Coastal Zone. Clarified application processing when in the coastal zone by requiring a local government or the Coastal Commission, as specified, to either approve or deny a coastal development permit application for an ADU within 60 days of receiving a completed application (Gov. Code, § 66329, subd. (a)).

• Size Limitations. Revised size limitations to be based on the square footage of interior living space of an ADU or JADU (Gov. Code, §§ 66321, subds. (b)(2) and (b)(3); 66313, subd. (d)).

• Fees. Specified that an ADU or JADU that contains less than 500 square feet of interior livable space does not increase assessable space. Revised the limitations on impact fees to prohibit impact fees on the development of an ADU that has 750 square feet of interior livable space or less or a JADU that has 500 square feet of interior livable space or less, and to require that any impact fee on an ADU that has more than 750 square feet of interior livable space be charged proportionately in relation to the square footage of the primary dwelling unit (Gov. Code, § 66311.5, subd. (c)).

• Expanded HCD Authority. Expanded HCD’s authority over Chapter 13 of Division 1 of Title 7 of the Government Code, to review, adopt, amend, or repeal guidelines to additionally grant that authority with respect to terms, references, and standards for JADUs (Gov. Code, § 66313.5).

• JADUs and Fire Sprinklers. Clarifies that fire sprinklers are not required for a JADU if the primary residence does not have fire sprinklers and that the addition of a JADU cannot trigger the requirement for fire sprinklers (Gov. Code, § 66323, subd. (d)).

• Unit Combinations. Specifies the number of allowable ADUs described under Government Code section 66323 per lot (Gov. Code, § 66323, subd. (a)).

• Certificate of Occupancy. Requires a local agency to issue a certificate of occupancy for an ADU constructed in a county that is subject to a proclamation of a state of emergency made by the Governor on or after February 1, 2025, even if the primary dwelling has not yet been issued a certificate of occupancy, if certain requirements are met, including that the primary dwelling was substantially damaged or destroyed by an event referenced in the state of emergency proclamation (Gov. Code, § 66328).

• Reasonable Restrictions. Specifies that reasonable restrictions in covenants, restrictions, and conditions, as described in the Civil Code, shall not include any fees or other financial requirements (Civil Code, § 714.3, subd. (b)).

• Objective Standards. Removes Government Code section 66323, subdivision (g), which allowed the imposition of objective standards on ADUs in multifamily dwelling structures if the local agency had adopted an ADU ordinance by July 1, 2018.

For questions or to request technical assistance, please visit HCD's ADU Portal.