ADDENDUM TO ACCESSORY DWELLING UNIT HANDBOOK

Over the years, State Accessory Dwelling Unit (ADU) Law has been revised to improve its effectiveness in creating more housing units. Changes to State ADU Law further reduced barriers to the development of ADUs and junior accessory dwelling units (JADUs). Within this context, the Department of Housing and Community Development (HCD) developed – and continues to update – the ADU Handbook to assist local governments, homeowners, attorneys, architects, builders, and the public in understanding and applying the requirements of state law. This document

serves as an addendum to the 2025 ADU Handbook to summarize and account for

recent legislation that amended State ADU Law.

AB 1154 (Chapter 507, Statutes of 2025) made various changes to State ADU Law (Gov. Code, § 66333) regarding JADUs and goes into effect on January 1, 2026. This bill:

Specifies 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)).

Requires that 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)).

SB 9 (Chapter 510 Statutes of 2025) made various changes to State ADU Law (Gov. Code, § 66326) regarding requirements for local jurisdictions when submitting ordinances to HCD and goes into effect on January 1, 2026. This bill:

Clarifies 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)).

(Chapter 520, Statutes of 2025) made various changes to State ADU Law (Gov. Code, §§ 66311, 66313, 66317, 66320, 66323; 66324; 66327; 66325; 66332 and added

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sections 6633.5;66335.5; and 66339.5) regarding requirements for local jurisdictions when submitting ordinances to HCD and goes into effect on January 1, 2026. This bill:

Revises the definition of a “junior accessory dwelling unit” to require the size of a JADU to be no more than 500 square feet of interior livable space (Gov. Code, § 66313, subd. (d)).

Expands HCD’s authority over Chapter 13 of Division 1 of Title 7 of the Government Code, including but not limited to review, adopt, amend, or repeal guidelines to additionally grant that authority with respect to terms, references, and standards for JADUs (Gov. Code, § 66311).

Revises the limitations on impact fees to, instead, prohibit impact fees upon the development of an ADU that has 750 square feet of interior livable space or less or 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, subds. (a) – (d)).

Requires a permitting agency to determine whether an application for an ADU or JADU is complete and provide written notice of the determination not later than 15 business days after the permitting agency received the application (Gov. Code, § 66317, subd. (a)(2)(A)).

Requires the permitting agency to provide the applicant with a list of incomplete items and a description of how the application can be made complete in the written notice if it is determined that an application is incomplete (Gov. Code, § 66317, subd. (a)(2)(B)).

Requires the permitting agency to provide a process for an application to be deemed complete and for applicants to appeal an incompleteness determination or denial, as provided, and requires the permitting agency to provide a final written determination by not later than 60 business days after receipt of the written appeal if a permit application is determined to be incomplete or is denied (Gov. Code, § 66317, subd. (d)(1)).

Specifies that an ADU or JADU that contains less than 500 square feet of interior livable space does not increase assessable space (Gov. Code, § 66311, subds. (d)). This is important to the calculation and imposition of school fees.

Revises size limitations to be based on the square footage of interior living space of the ADU (Gov. Code, § 66321, subds. (b)(2)(A), (b)(2)(B), and (b)(3)).

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

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)).

Adds section 66333.5, 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

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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.

(Chapter 491, Statutes of 2025) made various changes to State ADU Law (Gov. Code, §§ 66328 and 66329) regarding requirements for the issuance of a certificate of occupancy during a declared state of emergency and creating an exception in coastal jurisdictions. This bill went into effect on October 10, 2025, as an urgency bill. This bill:

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).

Clarifies application processing when in a 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)).

(Chapter 22, Statutes of 2025) made changes to the Civil Code and State ADU Law (Gov. Code, § 66323) regarding ADUs and went into effect on June 30, 2025. This bill:

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)).

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.

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