California AB 1154 Explained - New Rules Make Junior ADUs Easier to Build

California's AB 1154, signed into law by Governor Newsom in October 2025, is a game-changer for homeowners looking to build Junior Accessory Dwelling Units (JADUs) and small ADUs. The new law simplifies confusing rules, creates unified standards, and removes barriers that previously slowed down or blocked legally valid projects.

Here's what you need to know about AB 1154 and how it can help you add affordable housing to your property.

What Is AB 1154?

AB 1154, authored by Assemblymember Juan Carrillo and sponsored by California YIMBY, addresses a long-standing problem in California's ADU laws: the overlapping and sometimes contradictory rules governing small ADUs and Junior ADUs.

Before AB 1154, homeowners and local planning departments often struggled with:

• Confusing definitions of what qualified as a JADU vs. a small ADU
• Inconsistent standards across different code sections
• Slower approvals due to uncertainty about which rules applied
• Occasional denials of projects that should have been approved

AB 1154 fixes these issues by creating a more unified set of standards for ADUs under 500 square feet, giving homeowners clearer guidance and faster approvals.

What Is a Junior ADU (JADU)?

A Junior Accessory Dwelling Unit (JADU) is a small living space created within the walls of an existing single-family home, including attached garages. JADUs are an attractive option for many homeowners because they:

• Require less construction: Built within existing space rather than new construction.
• Cost less: Typically $50,000-$150,000 compared to $150,000-$400,000+ for detached ADUs.
• Have faster permitting: Simpler projects mean quicker approvals.
• Can share facilities: May share a bathroom with the main home, reducing costs.
• Avoid setback issues: No new building footprint means no setback concerns.

Under California law, JADUs must:

• Be no more than 500 square feet
• Be built within an existing or proposed single-family residence (including attached garages)
• Have a separate entrance from the main home
• Include an efficiency kitchen with cooking facilities, food prep counter, and storage cabinets

Key Changes Under AB 1154

1. Clarified Definitions

AB 1154 eliminates confusion between JADUs and small ADUs by creating clearer distinctions and ensuring that similar-sized units receive consistent treatment. Homeowners now have a more predictable path to approval regardless of whether they're building a JADU or a small attached ADU.

2. Unified Standards for Units Under 500 Square Feet

Previously, a 450-square-foot unit might face different requirements depending on how it was classified. AB 1154 creates more consistent standards for all small units, reducing the arbitrary differences that led to project delays and denials.

3. Reduced Owner-Occupancy Restrictions

Under AB 1154, owner-occupancy requirements are more limited:

• If your JADU has its own separate bathroom, owner-occupancy cannot be required
• Owner-occupancy may only be required when the JADU shares sanitation facilities with the main home
• Even when required, the owner can live in either the main home OR the JADU

This change provides significantly more flexibility for property owners who may want to rent out both units or live elsewhere.

4. Streamlined Permitting

By eliminating ambiguity in the rules, AB 1154 helps local agencies process JADU and small ADU applications more efficiently. When rules are clear, permit reviewers can make faster decisions with greater confidence.

Why JADUs Matter for California's Housing Crisis

California needs approximately 2.5 million new housing units to address its housing shortage. JADUs are a critical part of the solution because they:

Create Affordable Housing Naturally

JADUs typically rent for less than larger ADUs or apartments because they're smaller. This creates naturally affordable housing without requiring subsidies or income restrictions.

Work on Properties Where Detached ADUs Can't

Many California lots are too small or have setback issues that prevent construction of a detached ADU. JADUs, built within existing structures, avoid these constraints.

Require Lower Investment

The lower cost of JADU construction makes them accessible to more homeowners, including those who couldn't afford a $300,000+ detached ADU project.

Add Housing Without Changing Neighborhoods

Because JADUs are contained within existing structures, they add housing without visually changing the character of single-family neighborhoods—addressing a common concern about ADU construction.

Who Benefits from AB 1154?

Homeowners with Attached Garages

Converting an attached garage to a JADU is one of the most cost-effective ways to add rental income to your property. AB 1154 makes this process clearer and faster.

Homeowners with Unused Interior Space

Large homes with underutilized rooms, basements, or bonus spaces are prime candidates for JADU conversion. The new law ensures these projects won't get caught up in regulatory confusion.

Property Investors

The relaxed owner-occupancy requirements make JADUs more attractive for investment properties. Owners can now rent both the main home and the JADU in more circumstances.

Family Housing Situations

JADUs are perfect for multigenerational living—creating space for aging parents, adult children, or other family members while maintaining privacy and independence.

JADU vs. ADU: Which Is Right for You?

Feature	JADU	Detached ADU
Maximum Size	500 sq ft	800-1,200 sq ft
Location	Within existing home	Separate structure
Typical Cost	$50,000-$150,000	$150,000-$400,000+
Construction Time	2-4 months	6-12 months
Permit Timeline	30-60 days	60-90 days
Rental Income	$1,000-$2,000/mo	$2,000-$3,500/mo
Separate Bathroom	Optional	Required
Separate Entrance	Required	Required

Choose a JADU if:

• You want to minimize cost and construction time
• You have suitable space within your existing home
• You want to add modest rental income
• Your property has setback or lot coverage constraints

Choose a detached ADU if:

• You want to maximize rental income
• You prefer complete separation between units
• You have adequate lot space
• You want a larger unit for long-term rental or family use

How to Get Started with a JADU

1. Assess Your Space

Walk through your home and attached garage to identify potential JADU locations. Look for spaces that:

• Have or can have exterior access
• Are at least 220 square feet (minimum for efficiency units)
• Can accommodate an efficiency kitchen
• Have or can have adequate natural light and ventilation

2. Check Local Requirements

While state law sets minimum standards, your city may have additional requirements. Contact your local planning department to understand:

• Local JADU ordinances
• Permit fees and processing times
• Any design standards that apply
• Whether pre-approved plans are available

3. Plan Your Budget

Budget for:

• Architectural/design fees: $2,000-$8,000
• Permit fees: $500-$3,000
• Construction costs: $40,000-$120,000
• Kitchen installation: $5,000-$20,000
• Bathroom (if adding separate): $10,000-$25,000

4. Work with Experienced Professionals

JADUs may seem simple, but proper design and construction are essential for:

• Meeting building codes
• Maximizing the usable space
• Creating an appealing rental unit
• Ensuring long-term durability

The Bottom Line

AB 1154 represents California's continued commitment to making ADU and JADU construction easier for homeowners. By clarifying rules and removing unnecessary barriers, the law helps property owners create much-needed housing while generating rental income.

Whether you're looking to house a family member, generate passive income, or simply make better use of your property, a JADU may be the perfect solution—and AB 1154 makes it easier than ever to build one.

How LADU Can Help

At LADU, we specialize in helping California homeowners navigate the ADU and JADU construction process. Our team can help you:

• Evaluate whether a JADU or ADU is right for your property
• Design a unit that maximizes space and rental potential
• Navigate the permit process efficiently
• Construct a high-quality unit that meets all code requirements