California ADU Laws Explained: The Full Statute Stack

Why the "Statute Stack" Matters

Before 2020, whether you could build an ADU in California depended heavily on which city you lived in. Discretionary review, parking mandates, oversized setbacks, and owner-occupancy deed restrictions gave local governments plenty of tools to slow or stop projects. The legislature responded with a series of bills that set a statewide floor. Cities can be more permissive than state law, but they generally cannot be more restrictive on the points the statutes cover.

Understanding the stack matters for one practical reason: when a plan checker or a neighbor tells you something is not allowed, you need to know whether that is a real local rule or a leftover policy the state has already overridden. The laws below are presented in the order they took effect.

The 2020 Foundation: AB 68, AB 881, and SB 13

The modern ADU era begins with three bills that took effect in 2020 and rewired the approval process from the ground up. Together they made five changes that still define most ADU projects today:

1. Ministerial 60-day approval. ADU applications must be reviewed ministerially, meaning against objective checklists rather than discretionary hearings, and decided within 60 days. No design review boards, no public hearings, no neighbor vetoes.
2. A guaranteed 850 square feet. Homeowners are guaranteed the right to build an ADU of at least 850 square feet. Local size caps cannot cut below that floor.
3. Owner-occupancy requirements eliminated. Cities could no longer require the owner to live in either the main house or the ADU, which opened the door for investor-owned and fully rented properties.
4. Setbacks capped at 4 feet. Side and rear setbacks for ADUs were capped at 4 feet, which made narrow urban lots buildable for the first time in decades.
5. No replacement parking for garage conversions. When a garage is converted to an ADU, cities can no longer demand that the lost parking spaces be replaced elsewhere on the lot. This single change made the garage conversion the most cost-effective entry point into ADU ownership for many households.

In practice, these three bills turned the ADU from a permission you requested into an entitlement you exercised, provided your plans met the objective standards.

2023 Refinements: SB 897 and AB 976

AB 1033 (2024): Selling an ADU as a Condo

AB 1033 is the first law in the stack that changes what an ADU is rather than how it gets approved. It gives local governments the option to allow ADUs to be sold separately from the primary residence as condominiums. This is opt-in, not automatic, so the map matters: as of this writing, San Jose, Santa Monica, and both the city and county of San Diego have adopted it.

Where adopted, AB 1033 effectively lets a homeowner subdivide ownership of a single-family lot into two sellable homes. That reframes the ADU from a rental income play into a potential equity event, and it raises the stakes on design quality. A unit built to be sold gets appraised, inspected, and marketed like any other home, so floor plans, light, storage, and privacy separation from the main house all carry more weight than they would in a simple backyard rental.

If your city has not opted in, the traditional rule still applies: the ADU generally transfers with the main house. Check your local ordinance before building a pro forma around a separate sale.

AB 2533 (2025): Amnesty for Unpermitted ADUs

California has a large inventory of garage conversions and backyard units that were built without permits, often decades ago. AB 2533 created a legalization and amnesty path for unpermitted ADUs constructed before 2020 and placed limits on the penalty fees agencies can charge along the way.

For owners, the practical sequence usually starts with documentation: someone has to measure and draw the unit as it actually exists, then compare it against the standards it needs to meet. That is exactly what an as-built drawing set is for. Inspection requirements and the specifics of each amnesty program vary by jurisdiction, so treat AB 2533 as the door and your local building department as the hallway behind it. Our permit-ready drawings and as-builts service exists for precisely this situation.

SB 543 (2026): The Deemed-Approved Clock

The 60-day approval requirement has been on the books since 2020, but enforcement was the weak link. Some cities stretched the clock by sitting on applications or issuing slow, piecemeal completeness comments. SB 543 closes both gaps with two mechanisms:

• A 15-business-day completeness review. The agency must tell you whether your application is complete within 15 business days, which stops the tactic of letting submittals sit in a queue before the 60-day clock ever starts.
• Automatic deemed-approved status. If a city misses the 60-day clock on a complete application, the ADU application is deemed approved automatically. The remedy is no longer a complaint letter; it is the approval itself.

The homeowner's job under SB 543 is procedural discipline: submit a genuinely complete package, keep dated records of every submission and response, and know where you stand on the calendar. A drawing set with gaps invites a legitimate incompleteness finding and resets your leverage, so completeness is now a strategy, not just a courtesy.

What to Verify Locally Despite the State Floor

The statute stack sets minimums, not a complete rulebook. Before finalizing a design, confirm the local layer:

For a broader look at how California compares to other large states, see our companion guide, ADU Laws by State: TX, FL, NY, and CA.

Frequently Asked Questions

The Bottom Line

California's statute stack has steadily converted the ADU from a discretionary favor into a documented right: guaranteed size and setbacks in 2020, objective-standards-only review and permanent investor eligibility in 2023, a path to separate condo sales in 2024, amnesty for old unpermitted units in 2025, and an enforceable approval clock in 2026. The common thread across all of it is that the drawings now do the arguing. A complete, objective-standards-compliant plan set is what starts the clock, survives completeness review, and gets deemed approved if the city stalls.

This article is general information, not legal advice, and local requirements vary by jurisdiction. Apex Drafting Services prepares ADU plans and design packages for homeowners across California, working 100 percent remotely. Call us at (435) 668-1095 or start online.