Junior ADU (JADU) Rules and Costs in California 2026

A junior ADU, or JADU, is a small unit of up to 500 square feet built inside a single-family home. It can sit in an attached garage, too. It needs only a small kitchen and its own entrance, and it can share the main house’s bathroom. As of January 1, 2026, California also dropped the owner-occupancy rule for any junior ADU with its own bathroom. That change makes a JADU much more useful for Los Angeles homeowners who want a small rental or a private space for family.

This guide covers the current state rules, what a junior ADU costs in Los Angeles, how it compares with a full ADU, and how to keep the price down.

What counts as a junior ADU in California

First, state law defines a JADU narrowly. To qualify, the unit must meet all of these rules:

No more than 500 square feet of interior livable space. In 2025, SB 543 made clear that the limit is measured as interior livable space.
Fully inside a new or existing single-family home. An attached garage counts as part of the house. A detached garage, however, does not, so a unit there would be a regular ADU.
At least an efficiency kitchen. That means a cooking appliance, a prep counter and storage cabinets sized for the unit. Cities cannot ask for more.
Its own outside entrance. If the JADU shares a bathroom with the main house, it also needs an inside door to the main living area.
One per lot. A property can have only one junior ADU.

These rules live in California Government Code sections 66333 to 66339. In March 2026, the state housing department updated its ADU Handbook to match the latest changes.

What changed for junior ADUs in 2026

Owner occupancy now depends on the bathroom

Before this year, the owner had to live in either the JADU or the main house. AB 1154 took effect on January 1, 2026. Now the rule applies only when the junior ADU shares a bathroom with the main home. So if the JADU has its own bathroom, the owner does not have to live on site. Meanwhile, government agencies, land trusts and housing groups stay exempt either way.

In practice, the bathroom is now the biggest design decision in any JADU. A private bath costs more up front. However, it removes a rule that would otherwise follow the property.

Rentals must be longer than 30 days

AB 1154 also requires JADU rentals to run more than 30 days. In other words, a junior ADU is housing, not a short-term rental.

Deed restriction

Cities may require you to record a deed restriction. Under state law, it can cover only two things. First, the JADU cannot be sold apart from the house. Second, its size and features must follow state law.

Junior ADU versus ADU

Compare	Junior ADU	ADU
Maximum size	500 sq ft inside	Up to 1,200 sq ft detached
Location	Inside the house or attached garage	Detached, attached or converted space
Kitchen	Efficiency kitchen at minimum	Full kitchen
Bathroom	Can share with the main house	Must have its own
Owner on site	Only if the bathroom is shared	Not required
Separate utility hookup	Not required for conversions	Often required for new detached units
Impact fees	None	None under 750 sq ft
Typical cost in LA	Priced by scope; the lowest-cost way to add a unit	About $220,000 – $350,000 detached

Also, the two are not either-or. On most single-family lots in California, you can add a junior ADU inside the house and a detached ADU in the yard. For a wider comparison, see ADU versus home addition.

How much a junior ADU costs in Los Angeles

A JADU reuses existing walls, roof and foundation. For that reason, it is the lowest-cost way to create a separate unit. Still, the price varies widely, because the starting space varies so much. Instead of a single number, it helps to know which version you are building and what each one involves.

Bedroom conversion with a shared bath

Typically, the simplest version turns a bedroom or two next to a hall bath into a unit. The work usually includes an outside door, a small kitchen on one wall, an inside connecting door, new circuits, finishes and permits. Because the bath is shared, the owner must live on site.

Conversion with a private bathroom

A private bath removes the owner rule. However, it adds plumbing, waterproofing, tile and a fan, and it usually costs more than any other single part of the conversion. The price depends on how far the new bath sits from the existing drain lines. Our bathroom cost tiers for Woodland Hills and Calabasas show how finishes move that line.

Attached garage conversion

An attached garage is the most common junior ADU space in Valley ranch homes. To convert it, the crew insulates walls and ceiling and levels the slab. Then they replace the garage door with a wall, windows and an entry door, and add the kitchen, bath and circuits. A two-car garage is often bigger than 500 square feet. So the design may keep part of it as storage or give the extra space to the main house. Our garage conversion cost guide breaks down the shell work by garage size.

An attached garage JADU involves much of the same work as a full garage ADU conversion, which typically runs $140,000 to $200,000, so plan your budget closer to that range than to a simple bedroom conversion. Hillside sites, big structural changes, timing, material choices and selections can push the price higher.

What drives the cost of a junior ADU

Shared or private bath. This is now the biggest cost choice and the biggest rule choice.
Plumbing distance. A kitchen and bath near existing lines cost far less than ones that need a trench across a slab.
Electrical capacity. A 240-volt range, a mini-split and a water heater can push an older 100-amp service over its limit. On the other hand, a two-burner induction cooktop or a 120-volt heat pump water heater can avoid an upgrade.
Garage slab and insulation. Garage floors usually slope toward the door and sit below the house floor. So leveling, moisture control and insulation are real costs.
Fire safety and exits. Sleeping rooms need an escape window. In addition, the wall between a garage JADU and the rest of the garage needs fire-rated drywall.
Sound control. It is not always required. Even so, insulation in shared walls and a solid door make the unit much better for both households.

Permits for a junior ADU in Los Angeles

State law gives cities 60 days to approve or deny a complete JADU application. The review is ministerial, so there is no public hearing. In the City of Los Angeles, junior ADUs fall under LAMC Section 12.22 A.33 and go through LADBS. Similarly, cities in Ventura County and the San Fernando Valley follow the same state rules with their own forms.

A few state rules also help keep costs down:

No impact fees for a junior ADU.
No new utility hookup for a JADU inside an existing home. Also, connection fees cannot treat it as a new home.
No new parking. Some cities may ask about replacement parking when a JADU takes an attached garage, so check local rules before design.

Our ADU permitting process guide walks through plan submittal and corrections. The same steps apply to a JADU.

Is a junior ADU the right choice?

A JADU fits best when you have unused space inside the house. Good examples include a guest wing, a bedroom suite on an outside wall or an attached garage you no longer park in. It also fits families who want a parent, grown child or caregiver close by, without building a new structure.

By contrast, a full ADU is better if you want more than 500 square feet or a fully separate building. If rental income is the goal, run the numbers both ways. A junior ADU costs less, but a detached ADU usually rents for more. Our post on ADU rental profit covers what tenants pay for here.

Then start with a walkthrough of the space. The drain lines, the panel size and whether a private bath fits will show your cost tier before any drawings exist. You can also compare options on our ADU design and construction services page.

FAQ

Frequently Asked Questions

How big can a junior ADU be in California?

A junior ADU can have no more than 500 square feet of interior livable space. It must be fully contained inside a single-family home, which includes an attached garage.

Do I have to live on the property if I build a JADU?

Only if the JADU shares a bathroom with the main house. Since January 1, 2026, a junior ADU with its own bathroom no longer carries an owner-occupancy requirement in California.

Can I rent out a junior ADU on Airbnb?

No. California now requires JADU rentals to be longer than 30 days, so short-term rentals are not allowed.

Can I have a junior ADU and a regular ADU on the same lot?

On most single-family lots, yes. State law generally allows one JADU inside the house plus a detached ADU in the yard.

How much does a junior ADU cost in Los Angeles?

A junior ADU is priced by scope rather than by a single range. A bedroom conversion with a shared bath is the simplest version. A private bathroom adds plumbing and waterproofing, and an attached garage conversion involves much of the same work as a full garage ADU, which typically runs $140,000 to $200,000. Timing, materials and selections can push any version higher.

Planning a Junior ADU in Los Angeles?

Show us the space you want to convert, whether it is a bedroom suite or an attached garage. We will check the plumbing, the panel and the layout, and tell you which JADU option fits your home and budget.

Ready to start your project?

Schedule a consultation meeting today and get your project on the go!

We are glad to address any inquiries you may have. Please write us a few words about your project and we’ll set up a meeting with one of our project managers.