Do Local ADU Rules Override California State Law?

Local Rules vs. State Law: Who Wins on ADU Regulations?

One of the most confusing aspects of building an ADU in California is figuring out which rules actually apply to your project. Your city has its own ADU ordinance. The state has its own ADU laws. And sometimes, these two sets of rules conflict. When they do, which one wins?

The short answer is that California state law generally preempts (overrides) local ordinances when local rules are more restrictive than state standards. But the full answer is more nuanced, and understanding this nuance is critical if you want to protect your rights and avoid unnecessary obstacles during your ADU project.

In this comprehensive guide, we will break down the legal framework governing the relationship between state and local ADU regulations, identify the areas where state law clearly preempts local rules, highlight the areas where cities retain local authority, and explain what to do when you encounter a conflict between local and state requirements.

The California State ADU Legal Framework

California's ADU laws are primarily codified in Government Code Section 65852.2 (for ADUs) and Section 65852.22 (for Junior ADUs). These sections have been amended numerous times since the original ADU legislation passed in 2016, with major updates in 2017, 2019, 2020, 2022, and 2024.

The key principle underlying California's ADU legislation is that ADUs are a critical part of the state's strategy to address the housing crisis. The legislature has explicitly stated that local regulations that create unreasonable barriers to ADU construction are contrary to state policy. This policy direction is reflected in the preemption provisions built into the law.

Areas Where State Law Clearly Preempts Local Rules

The following requirements are set by state law, and cities cannot impose more restrictive standards:

Requirement	State Standard	Local Authority
Maximum rear/side setback	4 feet for detached ADU	Cannot require more than 4 ft
Minimum ADU size	Must allow at least 800 sq ft	Cannot require less than 150 sq ft
Maximum height	16 ft (detached), 18 ft (2-story)	Cannot be lower than state limits
Parking	Prohibited near transit, in many cases	Cannot require in exempted cases
Impact fees (under 750 sq ft)	Prohibited	Cannot charge any impact fees
Owner occupancy	Not required (since Jan 1, 2025)	Cannot require for new permits
Lot coverage/FAR	Must allow 800 sq ft regardless	Cannot deny based on coverage/FAR alone
Permit processing time	60 days from complete application	Cannot take longer without justification

Areas Where Cities Retain Local Authority

While state law sets the floor for ADU standards, cities do retain authority in certain areas. Understanding where local rules still apply is important for designing your ADU correctly:

Building Code Compliance

ADUs must comply with the California Building Code (CBC), California Residential Code (CRC), and all other applicable building codes. Cities can adopt local amendments to these codes (through a formal process), and ADUs must comply with those local amendments just like any other construction project.

Objective Design Standards

Cities can impose "objective" design standards on ADUs, meaning standards that can be applied without personal or subjective judgment. Examples include maximum roof pitch requirements, exterior material specifications (such as requiring stucco or wood siding), window placement rules based on measurable criteria, and color palette requirements. However, cities cannot impose subjective standards such as "architecturally compatible" or "neighborhood character" requirements, as these involve personal judgment and create unreasonable barriers.

Utility Connection Requirements

Cities and utility providers can establish requirements for how ADUs connect to water, sewer, gas, and electrical systems. These requirements must be reasonable and cannot be used as a de facto denial mechanism. However, connection fees and capacity requirements are within local authority, subject to the impact fee restrictions discussed above.

Fire and Life Safety

Local fire departments retain authority over fire safety requirements, including sprinkler systems, fire access, smoke and carbon monoxide detectors, and fire-rated construction requirements. These requirements must be based on the California Fire Code and cannot exceed what is required by state law for the type of construction proposed.

Common Conflicts Between Local and State ADU Rules

Based on our experience working with homeowners across California, here are the most common conflicts we see between local and state ADU regulations:

Conflict 1: Lot Coverage and Floor Area Ratio (FAR)

Many cities have lot coverage and FAR limits that would prevent adding an ADU. However, California law (Government Code Section 65852.2(c)(2)(C)) states that cities must allow at least an 800-square-foot ADU regardless of lot coverage and FAR limits. If your city is denying your ADU because it would exceed lot coverage or FAR limits, and your ADU is 800 square feet or less, state law protects your right to build. For ADUs larger than 800 square feet, lot coverage and FAR limits may apply.

Conflict 2: Rental Restrictions and Short-Term Rental Bans

Some cities have attempted to restrict how ADUs can be rented, including banning short-term rentals (less than 30 days). California law (Government Code Section 65852.2(e)(4)) specifically allows cities to prohibit short-term rental of ADUs. This is one area where local authority is explicitly preserved in the state law. However, cities cannot prohibit long-term rental of ADUs.

Conflict 3: Design Review Requirements

Some cities require ADU projects to go through a design review process before a building permit can be issued. Under California law, design review cannot be used to impose subjective design standards or to delay the permit process beyond the 60-day statutory timeline. If design review adds unreasonable time or imposes subjective requirements, it may violate state law.

Conflict 4: Conditional Use Permits and Variances

California law prohibits cities from requiring a conditional use permit (CUP) or variance for an ADU that complies with state standards. If your city is requiring a CUP or variance for a compliant ADU, this is a clear violation of state law. File a complaint with HCD if this occurs.

Conflict 5: Setback Requirements Beyond State Limits

Some cities still have ADU ordinances that require more than 4 feet of rear or side setback. This directly conflicts with Government Code Section 65852.2(a)(1)(D)(vii), which sets the 4-foot maximum. If your city is requiring greater setbacks, state law controls, and you have strong grounds for challenging the requirement. Be aware of how roof overhangs affect setback measurements in your jurisdiction.

HCD Enforcement of State ADU Law

The California Department of Housing and Community Development (HCD) plays a critical role in ensuring that local jurisdictions comply with state ADU law. HCD's enforcement powers include:

• Ordinance review: HCD reviews local ADU ordinances for compliance with state law and issues findings when ordinances are non-compliant
• Complaint investigation: Homeowners can file complaints with HCD when they believe a local jurisdiction is violating state ADU law
• Technical assistance: HCD publishes guidance memos and technical assistance documents to help cities interpret and implement state ADU law
• Referral to Attorney General: In cases of systematic non-compliance, HCD can refer matters to the California Attorney General for enforcement action

HCD has become increasingly active in enforcement. In recent years, HCD has reviewed and found non-compliance with dozens of local ADU ordinances, resulting in revisions to bring them into alignment with state law. The HCD ADU webpage provides valuable resources for homeowners navigating local vs. state requirements.

What to Do When Your City Violates State ADU Law

If you believe your city is applying local rules that conflict with state ADU law, here is a step-by-step approach:

1. Document everything: Keep copies of all communications, correction letters, and denial notices from the city
2. Research the law: Compare the city's requirement to the specific provision of Government Code Section 65852.2 that you believe it conflicts with
3. Request a meeting: Ask to meet with the supervising plan checker or planning manager to discuss the conflict. Sometimes, education resolves the issue
4. Cite HCD guidance: Reference HCD's published guidance memos and technical assistance documents to support your position
5. File a complaint with HCD: If the city does not resolve the issue, file a formal complaint with HCD
6. Consult an attorney: For significant disputes, retain a land use attorney who specializes in California ADU law. Learn more in our guide about what happens when a city denies your ADU application

Frequently Asked Questions

If my city has not updated its ADU ordinance since 2019, do the newer state laws still apply?

Yes. California state ADU law applies regardless of whether a city has updated its local ordinance. If the city's ordinance conflicts with current state law, state law controls. Cities are required to update their ordinances to comply with state law, and HCD actively monitors compliance. However, if your city has not updated its ordinance, you may need to educate city staff about the current state requirements.

Can my city require my ADU to match the architectural style of my main home?

Cities can impose "objective" design standards but not "subjective" ones. A requirement to "match" or be "compatible with" the main home is generally considered subjective and may violate state law. However, a requirement to use specific materials (such as stucco) or to meet specific dimensional standards (such as a maximum roof pitch) may be considered objective and enforceable. The distinction depends on whether the standard can be verified without personal judgment.

Does state law override HOA restrictions on ADUs?

Yes. California Civil Code Section 4751 (effective January 1, 2020) prohibits HOAs from imposing restrictions that effectively ban ADUs. While HOAs can impose reasonable architectural guidelines, they cannot prohibit ADUs or make construction infeasible through excessive restrictions. This applies to both existing CC&Rs and new rules adopted by the HOA.

Can my city require a public hearing before approving my ADU?

No. California law specifically prohibits cities from requiring a public hearing, neighborhood notification, or discretionary review for ADU applications that meet state standards. The ADU permit process must be ministerial (non-discretionary), meaning the city must approve applications that comply with objective standards without subjective evaluation or public input.

What if my city says my lot is too small for an ADU?

California state law does not impose a minimum lot size for ADUs on lots with an existing or proposed single-family dwelling. If your city has a minimum lot size requirement for ADUs, this may conflict with state law. Cities must allow ADUs on any lot with an existing or proposed residential use, regardless of lot size. However, the ADU itself must still meet setback, height, and building code requirements, which may practically limit ADU construction on very small lots.

Can a city charge me for a pre-application review of my ADU plans?

Cities can charge reasonable fees for pre-application consultations, but these fees should be modest (typically $50 to $200) and the pre-application process should not be mandatory. If a city requires an expensive pre-application review as a prerequisite to submitting an ADU application, this could be considered an unreasonable barrier to ADU construction under state law.

Recent Case Studies: When State Law Overrides Local ADU Rules

Understanding how California state preemption works in practice helps homeowners navigate conflicts between local and state ADU regulations. Here are several real-world examples that illustrate how the state has stepped in to enforce its ADU-friendly policies.

Case Study 1: Los Angeles Parking Requirements

In 2020, the City of Los Angeles attempted to require off-street parking for ADUs located within half a mile of public transit. California's AB 68 and SB 13 explicitly prohibit parking requirements for ADUs meeting certain criteria, including proximity to transit. After the state Department of Housing and Community Development (HCD) issued a notice of violation, Los Angeles revised its local ordinance to comply with state law. This case reinforced that cities cannot impose parking mandates that conflict with state exemptions.

Case Study 2: San Jose Lot Size Minimums

San Jose previously required a minimum lot size of 5,445 square feet for ADU construction. However, California Government Code Section 65852.2 does not allow cities to impose minimum lot size requirements for ADUs built on residentially zoned parcels. After HCD intervention, San Jose updated its rules to allow ADUs on any lot with an existing or proposed single-family home, regardless of lot size. This opened up ADU opportunities for thousands of homeowners on smaller parcels.

Case Study 3: Pasadena Design Standards

Pasadena enforced strict architectural design standards for ADUs, requiring specific roof pitches, exterior materials, and window placements that matched the primary dwelling. While cities can impose objective design standards, California law limits these standards to those that do not unreasonably increase the cost of construction. HCD found several of Pasadena's requirements went beyond what was reasonable, and the city was required to revise its design review process for ADU applications.

Case Study 4: Orange County Setback Disputes

Several Orange County cities attempted to maintain side and rear setback requirements of 10 feet or more for detached ADUs. Under state law, the maximum allowable setback for ADUs is 4 feet from the side and rear property lines. Cities that enforced larger setbacks received formal notices from HCD and were compelled to align their ordinances with the state standard. For homeowners in these areas, this change significantly increased buildable space on their properties. Learn more about setback requirements in our guide on setback rules for ADU roof overhangs.

Frequently Asked Questions

Can my city completely ban ADU construction?

No. Under California state law, cities cannot prohibit ADUs on residentially zoned lots with existing or proposed single-family or multifamily dwellings. If a city attempts to ban ADUs, the state can intervene through HCD to enforce compliance with Government Code Section 65852.2.

What happens if my city's ADU rules conflict with state law?

State law takes precedence over local ordinances when there is a direct conflict. If your city imposes restrictions that exceed what state law allows, such as larger setbacks, additional parking, or minimum lot sizes, you can file a complaint with HCD. The state agency will review the local rules and can compel the city to revise its ordinance. For more on the approval process, see our article on over-the-counter vs. plan check ADU approval.

Does state preemption apply to Junior ADUs (JADUs)?

Yes. California state law also preempts local regulations for Junior ADUs. Under Government Code Section 65852.22, cities must allow at least one JADU on any single-family lot, provided the JADU meets state criteria such as a maximum size of 500 square feet and being located within the existing primary dwelling or an attached structure.

Can my city impose special fees on ADU construction?

Cities are limited in what fees they can charge for ADUs under 750 square feet. For ADUs under 750 square feet, impact fees are generally prohibited. For larger ADUs, fees must be proportional to the size of the unit relative to the primary dwelling. Some cities still attempt to charge school impact fees or other assessments, so check our guide on school impact fees for ADUs in California.

How do I know if my city's ADU ordinance complies with state law?

You can check HCD's website for a list of cities that have submitted their ADU ordinances for review. HCD maintains records of which cities are in compliance and which have received notices of violation. You can also consult with an ADU specialist or builder who stays current on both state and local regulations.

What is the timeline for state enforcement against non-compliant cities?

After HCD identifies a non-compliant local ordinance, the city typically has 30 days to respond and outline a plan for coming into compliance. If the city fails to act, HCD can refer the matter to the Attorney General's office for further enforcement action. In practice, most cities revise their ordinances within 60 to 90 days of receiving an HCD notice.