The statewide ADU framework
California Government Code Section 65852.2 is the primary state law that governs ADUs. This statute creates a statewide baseline that applies to all cities and counties in California, regardless of local preferences or existing policies.
The law is designed to remove barriers to ADU construction by establishing clear, objective standards that local agencies must follow. Because it is a statewide law, local governments cannot impose more restrictive requirements than what the state allows.
The Housing and Community Development Department (HCD) publishes the ADU Handbook to provide official guidance on how to interpret and apply the statewide law. This handbook serves as the authoritative resource for both homeowners and local planning departments.
What state law requires
California state law establishes specific requirements that cities must follow:
Ministerial approval process
ADU applications must be processed ministerially, meaning without discretionary review. Cities cannot hold public hearings, ask for design review, or apply subjective judgment to approve or deny ADU permits.
Processing timelines
State law requires cities to process ADU applications on a specific timeline. For most ADU applications, the city must respond within 60 days or the application is deemed approved.
Basic size and setback standards
State law sets baseline standards for ADU size, setbacks from property lines, and other dimensional requirements. These standards are objective, not subjective.
Restrictions on local requirements
Cities cannot impose certain types of requirements, such as on-site parking in some cases, owner-occupancy in all units, or impact fees on small ADUs. These restrictions help reduce the cost and complexity of building ADUs.
What cities can still regulate
While state law removes many barriers, cities retain authority over certain aspects of ADU development:
- Application checklists and submittal formatting requirements
- Department workflow and permit processing procedures
- Local objective standards (such as setbacks or heights) that are no more restrictive than state law
- Design standards that are objective rather than subjective
- Inspection procedures and code compliance verification
- Building and electrical permits and final inspections
The key distinction is that local standards must be objective and applied consistently, not subjective or discretionary.
Key California ADU law changes
California ADU law has evolved significantly over the past few years. These are the major bills that shaped the current framework:
AB 68
Expanded ADU eligibility and reduced local restrictions on ADU approvals.
AB 881
Introduced the junior ADU (JADU) option, allowing smaller units in existing structures.
SB 13
Further clarified ministerial approval and set stricter limitations on what cities can regulate.
AB 2221
Expanded ADU opportunities and removed additional local barriers to ADU projects.
SB 897
Made changes to owner-occupancy rules and clarified JADU requirements.
2026 HCD Addendum
HCD published updates covering new changes and clarifications effective in 2026.
Owner occupancy rules
Owner-occupancy requirements for ADUs have changed significantly over the past few years as state law has evolved.
Historically, some earlier versions of ADU law included owner-occupancy requirements. As of the most recent updates, state law generally does not require an owner to occupy either the primary home or the ADU.
However, JADUs (junior ADUs) do have owner-occupancy requirements. For a JADU, at least one of the units—either the primary home or the JADU—must be owner-occupied.
Local policies may also impose additional owner-occupancy rules where state law allows. Always check your local planning department's ADU guidelines to understand what rules apply in your city or county.
Impact fees and ADUs
State law places strict limits on what impact fees cities can charge for ADU projects.
For ADUs smaller than 750 square feet, state law prohibits cities from charging impact fees entirely. This is a significant cost savings for most ADU projects.
For ADUs 750 square feet or larger, cities can charge impact fees, but only on a proportional basis. The fee must be proportional to the square footage of the ADU compared to the primary residence. For example, if an ADU is half the size of the primary home, the city can only charge half of the impact fee.
Some fees may still apply, such as sewer connection fees or other utility charges. Your local planning department can provide a complete list of what fees apply to your specific project.
How HCD enforces ADU law
The California Housing and Community Development Department (HCD) plays an important role in ensuring that local agencies follow state ADU law.
HCD provides technical assistance to local planning departments and publishes guidance documents like the ADU Handbook. HCD also reviews local ADU ordinances to ensure they comply with state law.
Local agencies are required to submit their ADU ordinances to HCD for review. If HCD determines that a local ordinance does not comply with state law, it can work with the local agency to bring the ordinance into compliance.
If you believe your local planning department is not following state ADU law, you can contact HCD or consult with a qualified attorney familiar with ADU regulations.
Common mistakes homeowners make
Here are the most frequent mistakes we see:
Assuming all cities have the same rules
Each city implements state law differently. Rules in one city do not apply to another. Always check your specific local planning department.
Not checking the local planning page first
Most cities publish ADU guidelines on their planning department website. This is the fastest way to understand what your city requires.
Treating SB 9 and ADU law as the same thing
SB 9 allows property splits and is separate from ADU law. They serve different purposes and have different requirements.
Ignoring Title 24 and Energy Code
ADUs must comply with California's Energy Code (Title 24). This affects insulation, windows, HVAC, and other systems. Budget for these costs early.
Starting design before understanding local requirements
Meet with your local planning department first, understand the rules, and then start design. This saves time and money down the line.
Recommended next steps
Once you understand state law, explore these related topics:
This page is for general educational purposes only. California ADU law, city implementation, and code requirements can change. Always verify project-specific requirements with the relevant planning department, building department, and qualified professionals.