What changed in California’s ADU rules — the section-by-section change log

Why a change log, rather than another summary of the law

Almost every page about California ADU law is a description of the rules as somebody understood them on the day they wrote it. Almost none of them tell you when that day was, and none of them tell you what moved afterwards.

That is a specific and expensive failure. A homeowner reading a 2023 article about Government Code § 65852.2 is reading about a section that no longer exists. A designer citing § 66332 in a permit narrative is citing a number that was retired on 1 January 2026.

A city planner who last checked the fee rules under § 66324 is looking for a section the code will not return.

In every one of those cases the substance of the rule may be entirely unchanged — the fee exemptions in what is now § 66311.5 still turn on the same 750 and 500 square foot thresholds — but the citation is dead, and a dead citation is what an official uses to send an application back.

So this page does the boring thing properly. It records, for every section in the chapter, which bill last touched it, which section of that bill did the touching, and the date the current text took effect.

It records the numbers that no longer resolve and what replaced them. And it records how each of those facts was established, because a change log whose provenance you cannot check is just another article with a date on it.

HyreADU method. Every row below was obtained by requesting that section individually from the Legislative Counsel’s codes_displaySection service and reading the enactment line the service prints at the foot of the section.

Where a section number returned no code text, that is recorded as an absence rather than inferred. Bill chaptering dates come from the Chaptered Date field on each bill’s own status page.

Nothing on this page was carried over from an existing page on this site without being re-requested, and nothing was written from memory.

The shape of the chapter today

California’s accessory dwelling unit law lives in Government Code Chapter 13, sections 66310 to 66342, in four articles. The chapter itself is only two and a half years old.

Article 1, General Provisions (§§ 66310–66313.5), holds the legislative findings, the charter-city rule, the definitions, the fee section and the protection for unpermitted units built before 2020.

Article 2, Accessory Dwelling Unit Approvals (§§ 66314–66331), is the working half of the chapter: what an ordinance may contain, the size and height floors, the parking exemptions, ministerial approval, the preemption machinery and HCD review.

Article 3, Junior Accessory Dwelling Units (§§ 66333–66339.5), is the JADU equivalent. Article 4, Separate Sale or Conveyance (§§ 66340–66342), is the narrow route by which an ADU can be sold apart from the house.

HyreADU calculation. Of the 36 sections, 18 still show "Added by Stats. 2024, Ch. 7, Sec. 20. (SB 477)" and nothing else. 18 show a later bill.

Of those 18, 17 were touched by one of the four bills chaptered on 10 October 2025, and the remaining one was touched by AB 1170, a maintenance-of-the-codes bill chaptered on 28 July 2025.

The distribution is uneven in a way that is worth noticing. Article 4, on separate conveyance, is untouched — three sections, all still original.

Article 3, on junior units, is the opposite: SB 543 amended one section, created three, and AB 1154 amended a fourth, so the JADU article grew from seven sections to ten in a single legislative year.

If you had to guess where the drafting attention went in 2025, the section counts would tell you before the bill text did.

SB 543 did more than renumber

SB 543 (McNerney), Stats. 2025, Ch. 520, is the bill everyone remembers for the renumbering. Reading its thirteen code sections together shows something else.

Three of its thirteen sections are the renumberings. Three more create sections that did not exist before. Seven amend sections in place. Set the three new sections beside the ADU article and the pattern is immediate.

New § 66333.5 requires a local agency to submit its JADU ordinance to HCD within 60 days of adoption, lets HCD issue written findings of non-compliance, and gives the agency no more than 30 days to respond. That is, clause for clause, the machinery § 66326 already applied to ADU ordinances.

New § 66335.5 provides that where a local agency has not adopted a JADU ordinance and receives an application, it must approve or disapprove ministerially. That is what § 66320 already did for ADUs.

New § 66339.5 provides that the JADU article supersedes a conflicting local ordinance, and that agencies remain free to be less restrictive. That is § 66325, word pattern and all.

HyreADU analysis. The most defensible reading is that SB 543 was a parity exercise: the junior unit article had the substantive rules but not the enforcement and default machinery, and the bill gave it all three of the mechanisms that make the ADU article self-executing.

The practical consequence, for a homeowner, is that the three arguments that already worked for an ADU — your city has no ordinance so the state rule applies; your city’s ordinance conflicts so it is superseded; HCD reviews your city’s ordinance and can find it non-compliant — now have JADU equivalents with their own section numbers.

We describe this as our reading of the amended text, not as a statement of legislative intent, which we did not attempt to establish.

SB 543 also tightened the front of the ADU process. As amended, § 66317 requires a permitting agency to determine whether an application is complete and give the applicant written notice within 15 business days, with a list of the incomplete items and a description of how to cure them.

Section 66335, as amended by the same bill, imposes the identical 15-business-day completeness rule on junior units. That is a deadline that did not previously sit in front of the 60-day decision clock.

The bill that did not wait for January

California bills passed in the ordinary course take effect on 1 January of the following year. AB 462 took effect on 10 October 2025, the day it was chaptered, and it is the only 2025 ADU bill that did.

What AB 462 changed is § 66328, the rule that a local agency may not issue a certificate of occupancy for an ADU before it issues one for the primary dwelling. The general rule survives.

The bill added an exception: in a county subject to a proclamation of a state of emergency made by the Governor on or after 1 February 2025, an agency shall issue a certificate of occupancy for an ADU even though the primary dwelling has none, provided the primary dwelling was substantially damaged or destroyed by an event referenced in the proclamation and the ADU has been permitted and has passed all required inspections.

The exception does not apply to an ADU attached to the primary dwelling.

HyreADU analysis. The 1 February 2025 cut-off and the immediate effective date point the same way.

The provision is written for households whose main house is gone and whose backyard unit is finished — a family that could move back onto their own lot months earlier if the certificate were not withheld.

Making it operative in October rather than January is what you would do if you wanted it available during a rebuild that was already under way.

We are reading the structure of the amendment, not asserting a legislative motive we did not verify.

AB 462 also amended § 66329, the section governing the chapter’s relationship to the California Coastal Act, on the same date.

The practical point for anyone reading a rebuild timeline. If you are working from a summary of California ADU law written between January and October 2025, the certificate-of-occupancy sequencing rule in that summary is the unqualified version, and for a disaster-area rebuild it is now wrong in the direction that costs the household months.

Where the retired numbers are still in circulation

Stale ADU section numbers are not a hypothetical problem, and they are not confined to blogs. Official material carries the old numbers too.

The clearest instance this desk has recorded is the City of Oakland’s own page on legalizing an unpermitted accessory or junior accessory dwelling unit, which cites Government Code § 66332 as the legal basis for its amnesty tracks.

Section 66332 was renumbered to § 66311.7 with effect from 1 January 2026. When this desk retrieved that page on 5 September 2026 for the legalization study, the old number was still there.

We say this without any suggestion of fault. A renumbering carried out in October and operative in January leaves every municipal handout, permit checklist, plan-set narrative and standard-conditions template in the state pointing at an address that has moved.

Nothing about Oakland’s program is affected: § 66311.7 carries the same operative text, barring denial of a permit for a pre-2020 unpermitted unit on building-standard or ordinance-compliance grounds, and forbidding impact fees except in the narrow circumstances the section names. The rule is intact. The pointer is stale.

HyreADU analysis. The failure mode worth planning for is asymmetric. A stale citation in a city’s favor is usually caught, because an applicant reads it closely.

A stale citation in an applicant’s favor is usually not caught at all, because the person who would benefit from correcting it is the one who wrote it.

That is the argument for carrying the current number and the retired one together in any document you submit — “Government Code § 66311.7 (formerly § 66332)” costs four words and removes the whole exchange.

It is also the argument for this page having a date on every row rather than a date at the top.

What this page does not tell you

Four limits, stated plainly, because a register that overstates its own coverage is worse than no register.

It is a record of state statute, not of local ordinances. Every California jurisdiction is amending its own ADU code against a floor that moved twice in twenty-two months, and those local changes are not in this register.

The ordinance tracker is where that work sits, and it is honest about how few jurisdictions it has been able to read.

It records that a section changed, not everything that changed inside it. An amendment can add a subdivision, delete one, or move a comma.

Where this page describes what an amendment did — SB 543’s new JADU sections, AB 462’s disaster exception, the 15-business-day completeness notice — it is describing the operative text we retrieved and read.

For the sections we list without describing, the register tells you the text moved and gives you the section to read; it does not summarize a change we have not characterized.

It reaches no compliance conclusion about anybody. Whether a particular local ordinance complies with the chapter is a finding for the Department of Housing and Community Development under § 66326, and a preemption conclusion is a court’s. This page names no jurisdiction as non-compliant.

It is current to one date. Everything here was retrieved on 2026-09-07. The chapter has been amended by six bills in two and a half years; assuming it will stay still is the mistake this page exists to make harder.