California ADU Laws Going Into 2026: What Homeowners Need to Know

It’s a new year, which means a new round of ADU laws hitting California. By now, this pattern should feel familiar. Since 2017, California has passed new ADU legislation nearly every year to make it easier, faster, and more affordable for homeowners to build.

And there’s a reason for that: ADUs work.

After designing and building over 100 ADUs, I’ve seen firsthand how life‑changing these units can be for homeowners, renters, and families trying to stay in place while creating long‑term value. That’s why I’m back with another breakdown of the most important ADU laws you need to know as we head into 2026.

Before we dive in, a quick introduction. My name is Joseph Peretz, and I’ve spent the last seven years working exclusively in the ADU space, designing and building ADUs, and helping homeowners understand the process so they can avoid delays, unnecessary costs, and bad information. If you still have questions after reading this, I offer free 15‑minute phone consultations to help homeowners figure out their next steps. You can sign up here.

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Now, let’s get into the laws that matter.

The 3 Most Important ADU Bills for 2026

There are quite a few bills this cycle that touch ADUs in some way, but to keep things simple, this article focuses on the three most impactful:

• SB 543

• AB 1154

• AB 462

Bill #1: SB 543 — Major Clarifications That Matter in the Real World

SB 543 is the most important bill this year because it clears up confusion that has been causing real problems on real ADU projects.

ADU and JADU Size: Interior Livable Space Clarified

Until now, state law said cities could not prevent homeowners from building at least:

• An 800 sq ft ADU, and

• A 500 sq ft JADU

But the law was vague about what “square footage” actually meant. Some less ADU‑friendly cities took advantage of that vagueness and rejected applications based on total building footprint instead of livable space.

SB 543 fixes this.

Going forward, when ADU and JADU laws refer to size, they are referring specifically to interior livable space.

That means things like:

• Wall thickness

• Exterior staircases

• Covered patios

• Roof overhangs

should not count against your maximum square footage.

For example, if your ADU structure measures 820 sq ft but the interior livable space is 800 sq ft, your project should now comply with state size limits.

And remember, small ADUs can still be incredible living spaces. Smart design matters far more than raw square footage.

Impact Fees: Another Big Clarification

Under existing law, ADUs under 750 sq ft are exempt from development and impact fees, which can easily add up to tens of thousands of dollars.

SB 543 makes it crystal clear that this exemption is also based on interior livable space, not total building footprint.

That means:

• 750 sq ft or less of interior livable space = no development or impact fees

There’s also an additional savings opportunity:

• If your ADU or JADU has 500 sq ft or less of interior livable space, it is also exempt from school impact fees

Depending on the city, this alone can save homeowners tens of thousands of dollars.

How Many ADUs Can You Build on One Lot?

This has been a long‑standing point of confusion. Under existing law, a single‑family lot can include:

• One converted ADU

• One JADU

• One detached ADU

The problem wasn’t the law. It was whether cities had to allow these in combination.

SB 543 doesn’t change the statewide limits, but it closes loopholes cities were using to slow projects down or quietly block them.

If a city has not adopted a compliant ADU or JADU ordinance, it is still required to:

• Process ADU and JADU applications ministerially

• Approve or deny applications within required timelines

SB 543 tightens enforcement around these requirements.

What “Ministerial Approval” Actually Means

A ministerial review means the city can only check your project against objective, written standards, such as:

• Setbacks

• Height limits

• Size limits

There is:

• No public hearing

• No design review board

• No subjective opinions about whether the city “likes” your project

If your plans meet the rules, the city must approve them.

New 15‑Day Completeness Deadline

This is one of the biggest procedural changes in SB 543. Once you submit an ADU or JADU application, the city now has:

• 15 business days to determine whether your application is complete

• That determination must be provided in writing

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If the city claims your application is incomplete, they must:

• List exactly what is missing

• Explain how to fix it

• Allow you to resubmit

  
  

Important clarification: this does not replace the 60‑day approval timeline. The 15‑day rule applies only to determining whether the application is complete.

If a city denies your application or unfairly claims it is incomplete, SB 543 now requires:

• A formal appeal process

• A final written decision within 60 business days of the appeal

No more endless limbo.

Two Final SB 543 Clarifications

• If your primary home does not require fire sprinklers, neither does your ADU or JADU

• Cities generally cannot require new or separate utility connections for ADUs or JADUs unless very specific exceptions apply

These rules prevent cities from quietly killing projects through unnecessary costs.

Bill #2: AB 1154 | A Big Win for JADUs

AB 1154 focuses on Junior Accessory Dwelling Units (JADUs) and fixes a rule that has limited their usefulness.

Previously, if you built a JADU, the law required owner‑occupancy of the main home. In other words, you had to live on the property.

AB 1154 partially removes that requirement.

Going forward:

• Owner‑occupancy is only required if the JADU shares a bathroom with the main house

• If the JADU has its own separate bathroom, the city cannot require owner‑occupancy

This change makes JADUs far more flexible as long‑term rental units.

Bill #3: AB 462 | Coastal ADUs (Huge for Los Angeles)

Even though ADUs are allowed statewide, properties located in the coastal zone have faced major delays due to the California Coastal Act.

Historically, homeowners needed a Coastal Development Permit (CDP) to build an ADU, adding:

• Months or even years of delays

• Additional hearings

• Significant extra costs

AB 462 changes that.

This bill exempts certain ADUs from requiring a Coastal Development Permit, specifically in:

• Los Angeles County

• Any county subject to a state of emergency declared by the Governor on or after February 1, 2025

If you qualify, you can build an ADU without going through the Coastal Commission process.

This law applies to all cities, including charter cities, and cities cannot opt out. AB 462 is an urgency statute, meaning it is already in effect.

Final Thoughts

Many of the ADU laws passed in recent years aren’t flashy. They’re about closing loopholes cities have used to slow or block ADU construction. While these changes may seem small on paper, they can make a huge difference, especially in stricter cities.

If you’re planning to build an ADU in 2026, understanding these laws can save you time, money, and frustration.

If you have questions about your property or project, feel free to sign up for a free 15‑minute phone call. I’m always happy to talk through your options and help you figure out the best path forward.

See you on the next one.