What Is California ADU Law?

Key takeaways

• California ADU law now lives in Government Code Sections 66310 to 66342, called Chapter 13.
• The old Section 65852.2 was repealed on 25 March 2024. Rules it held now have new numbers.
• Some sections moved again on 1 January 2026. Fees are now in Section 66311.5.
• State law sets the outer limits. Your city can be looser, but not stricter.
• A city must approve a compliant ADU without a hearing, on a set clock.
• These rules apply in California only. Other states have their own rules, or none.

What it means, in plain English

Think of California ADU law as a rulebook the state hands to every city. It says what a city must let you build. It also says what a city is not allowed to ask of you.

A statute is a law passed by the Legislature. The ADU statutes sit in one block of the Government Code. Lawyers call that block "Chapter 13". It runs from Section 66310 to Section 66342.

Two more legal words show up a lot. A ceiling is the strictest rule a city may use. Ministerial review means a planner checks your plans against fixed rules, with no hearing and no room for opinion.

Why it matters to you

If you own a home in California, this law decides a lot before you ever talk to a designer. It limits how far back from the fence a new ADU must sit. It limits parking. It bars a rule that you must live on site to rent the ADU.

It also gives you a footing in any dispute. When a city rule looks stricter than the state rule, you can ask the city to explain it. An ordinance that breaks the state rules is void, and the state rules apply instead ⁵.

Finally, it tells you what to cite. Old guides still quote Section 65852.2. If you quote a repealed section to a planner, you lose time. Quote the current Chapter 13 number.

How the law works on a real application

1. You check your lot against the city's ADU rules and the state ceilings.
2. You file a complete ADU application with the city or county.
3. The city tells you in writing within 15 business days if anything is missing ⁶.
4. A planner checks the plans against objective rules only. No hearing is held.
5. The city approves or denies within 60 days of a complete application, where a home already exists on the lot. If it does neither, the application is deemed approved ⁶.
6. You then get the building permit and build.

The 60-day clock and the deemed-approved rule are in Section 66317. Check the current text before you rely on a date.

What the state law actually does

Most land-use rules in the United States are local. A city decides what can be built in each zone. California carved ADUs out of that system: the Legislature declared ADUs "an essential component" of the state's housing supply in Section 66310 ¹ and then wrote the limits that local rules must stay inside.

The law works in three layers. First, it lets a city or county adopt its own ADU ordinance, but only with objective standards that do not exceed the state ceilings in Section 66314 ³.

Second, Section 66315 says those standards are the maximum: no extra standards may be added, "including an owner-occupant requirement" ⁴.

Third, an ordinance that fails to comply is "null and void", and the agency must apply the state standards until it adopts a compliant one (Section 66316) ⁵.

The diagram stacks those layers in order. When a city rule seems to conflict with state law, start at the top and work down.

Section 66312 extends the whole chapter to charter cities ², so a city's charter status does not exempt it.

For the plain-language overview of every rule in force, the ADU regulations hub is the place to start.

What the state sets and what the city still decides

Sources: [3] [4] [6] [7]

Where Section 65852.2 went

How to read an older citation

City handouts, loan guidelines and blog posts written before 2024 still cite "65852.2(e)" or similar. The rule they describe usually still exists, under a new number.

A handful of mappings help: the old fee and connection rules are now in Section 66311.5 ⁷; the junior ADU ordinance rules sit in Article 3, starting at Section 66333 ⁹; HCD's authority to issue guidelines is now Section 66313.5 ⁸.

The SB 543 move of 66327 to 66313.5 is the weakest mapping to rely on: the current 66313.5 is a short section about HCD guidelines, so check that the rule an old document describes is really the one in that section before citing it.

Do not prefix-match. Sections 65852.21, 65852.23 and 65852.27 are separate, live sections with different subjects, not pieces of the old ADU section. And when a document says "SB 9", name the year: the 2021 lot-split SB 9 and SB 9 of 2025 are different bills.

How state law reaches a permit

1. Chapter 13 sets ceilings
2. local ADU ordinance adopts objective standards within them
3. HCD reviews the ordinance
4. ministerial approval of the application
5. ADU building permit

A worked example: one owner, three checks

A hypothetical California owner plans a 700 sq ft detached ADU behind an existing house. Here is how the current sections answer three common questions.

This is an example of method, not a ruling on any real lot. The planning department applies the rules.

Sources: [3] [7] [6]

Where you will see it

• City ADU handouts. Look at the section numbers they cite. Older ones still say 65852.2.
• Plan check comments. A planner may cite a Chapter 13 section when asking for a change.
• Fee letters. Impact fee and connection fee rules now cite Section 66311.5.
• Lender and appraisal notes. Some mention whether the ADU is legal under state law.
• HCD letters to cities. When the state finds an ordinance out of line, it cites the current sections.

What the state law does and does not do

State law, local ordinance and building code compared

Common misreadings

Myth "Section 65852.2 is the California ADU law."

Reality It was, until 25 March 2024. SB 477 repealed it and moved the content to Chapter 13 ⁴.

Myth "State law means my city has no say."

Reality Cities still adopt ordinances with objective standards on height, setbacks, landscaping and design. They cannot exceed the state ceilings or add discretionary review ³.

Myth "A charter city can opt out."

Reality Section 66312 applies the chapter to charter cities ².

Myth "These rules apply in every state."

Reality They are California's. Other states have their own statutes, or none.

What to ask your city

• Which version of your ADU ordinance is in force, and when was it adopted?
• Has HCD sent the city any findings about the ordinance?
• Which current Chapter 13 section supports this requirement?
• Is this rule an objective standard, or does it need a judgment call?
• When did my application become complete, and what is the decision date?
• Which fees on my estimate are impact fees, and which are connection fees?

Checklist for your project

1. Find the city's ADU ordinance and note its adoption date.
2. Read the state ceilings for size, setbacks and parking in the current sections.
3. Mark any local rule that looks stricter than the state rule.
4. Swap any old 65852.2 citation in your notes for the current section.
5. Keep a dated copy of your complete application and the city's letters.
6. Track the 15-business-day and 60-day clocks.
7. Ask the planner in writing about any rule you think conflicts with state law.

Outside California

Go deeper

• ADU statute change logEvery amendment to the chapter, dated, with the bill
• California ADU ordinance trackerHow individual city ordinances line up with state law
• California ADU enforcement recordWhat happens when a city does not comply
• ADU feasibility checkerTest a lot against the state ceilings

Related terms

Local ADU Ordinance

A local ADU ordinance is the section of a city or county's zoning code that sets the rules for accessory dwelling units in that jurisdiction: where they are allowed, how big and tall they can be, setbacks, design standards and the application process.

Ministerial Approval

Ministerial approval is a permit decision in which an official checks an application against fixed, objective standards and must approve it if they are met, with no public hearing and no discretion to deny it on judgment.

ADU Owner-Occupancy Requirement

An ADU owner-occupancy requirement is a local rule that the property owner must live in either the main house or the accessory unit, so that both units cannot be rented to other people at the same time.

ADU Parking Requirement

An ADU parking requirement is a local zoning rule that a new accessory dwelling unit must come with a set number of off-street parking spaces, usually on the driveway or elsewhere on the lot.

Junior ADU

A junior ADU (JADU) is a small home of no more than 500 square feet carved out of an existing or proposed single-family house, with its own entrance and an efficiency kitchen, and permission to share the main home’s bathroom.

ADU Permit

An ADU permit is the building permit a city or county issues to allow construction of an accessory dwelling unit, after checking the plans against local zoning standards and the building code.

ADU Size

ADU size is the floor area of an accessory dwelling unit, usually counted as interior livable square feet, and it is the number that state and local rules cap, protect and use to set fees.

Setback

A setback is the minimum distance a zoning code requires between a building and a property line, measured horizontally from the line to the nearest wall or other regulated part of the structure.

ADU Regulations

The state laws and local ordinances that decide whether, where and how big an ADU can be built.

Also referenced from: Accessory Dwelling Unit, Junior ADU, Manufactured ADU, Zoning Code, Minimum Lot Size, Planning Approval, California Building Code, Local ADU Ordinance, ADU Owner-Occupancy Requirement, ADU Parking Requirement, Short-Term Rental ADU