JADU vs ADU in California: Size, Rules, Cost and Which to Build

California recognizes two kinds of backyard and in-home units. The accessory dwelling unit (ADU) and the junior accessory dwelling unit (JADU) sound similar, but they follow different rules on size, location, bathrooms, owner occupancy and fees. Choosing the right one can save you tens of thousands of dollars.

This guide is based on the California Department of Housing and Community Development's ADU Handbook (March 2026) and Government Code sections 66313 and 66333. Local ordinances add their own details, so always confirm with your city.

The quick comparison

• Size: a JADU is no more than 500 sq ft of interior living space. An ADU can be much larger. Local rules must allow at least 850 sq ft (1,000 sq ft for more than one bedroom), and state default limits reach 1,200 sq ft for a detached unit.
• Location: a JADU must sit entirely within the walls of a single-family home, which includes an attached garage. An ADU can be detached, attached, or converted from the house or an accessory structure.
• Kitchen: a JADU needs at least an efficiency kitchen, meaning a cooking appliance, a prep counter and storage. An ADU has a full kitchen.
• Bathroom: a JADU may share a bathroom with the main house or have its own. An ADU has its own.
• Property type: JADUs are for single-family homes. ADUs can also go on multifamily lots.
• Deed restriction: a JADU requires a recorded deed restriction that bars selling it separately and limits its size and attributes.
• Rentals: both must be rented for more than 30 days if rented at all, so short-term rentals are out.

Owner occupancy changed in 2026

This is the biggest recent change. Under AB 1154, effective January 1, 2026, a local agency may require owner occupancy for a JADU only if the JADU shares sanitation facilities (a bathroom) with the main home. The owner can live in either part.

If the JADU has its own bathroom, cities cannot require owner occupancy. HCD's March 2026 Handbook addendum confirms this, along with the ban on JADU rentals of 30 days or less.

For regular ADUs, Government Code section 66315 already bars owner-occupancy requirements. The one exception is the narrow case of ADUs sold separately under section 66341.

Entrances

A JADU needs a separate entrance from the main entrance of the home. If it doesn't have its own bathroom, it must also have an interior door to the main living area, so the occupant can reach the shared bathroom.

Fees and utilities

JADUs are cheap on fees:

• No impact fees for JADUs of 500 sq ft or less.
• No separate utility connection or capacity charge.
• No required parking.

ADUs of 750 sq ft or less also avoid impact fees.

Cost: why JADUs are the budget option

A JADU reuses your existing roof, foundation and walls, usually a spare bedroom, a primary suite or an attached garage. Typical SoCal projects run $50,000–$150,000. The big variable is whether you add a full bathroom and how much electrical and plumbing work you need.

A garage-conversion ADU usually costs more, and a new detached ADU often costs $200,000 or more. See our cost guide and estimator.

Can you have both?

Yes. State law allows, on a single-family lot:

• one ADU (detached, attached or converted), plus
• one JADU, plus
• in many cases, one additional detached new-construction ADU of up to 800 sq ft (a "66323 unit").

HCD's Handbook explains these combinations. Owners in Los Angeles, San Diego and the Inland Empire are increasingly building a JADU for family members and a detached ADU for rental income.

When a JADU makes sense

• You want a space for an aging parent or an adult child, with privacy and a small kitchen, but you don't need a separate structure.
• Your budget is under about $150,000.
• You live in the house and are fine sharing a bathroom (remember, owner occupancy applies when sanitation is shared).
• Your lot has no room for a detached unit, or it's steep.

When a full ADU makes sense

• You want the best rental income or resale value.
• You want full separation for privacy.
• You may move out and rent both the house and the unit. An ADU never requires owner occupancy, and a JADU with its own bathroom no longer does either.
• You want more than 500 sq ft or a second bedroom.

The conversion path

Some owners start with a JADU and later expand. Because a JADU must stay within the walls of the home, growing past 500 sq ft generally means re-permitting it as an attached ADU. Talk to your builder about planning the electrical, plumbing and fire separation for that future.

Find a builder

Many builders in our directory do both JADUs and conversions. Look for an active CSLB license (our badge shows a confident match to a current CSLB record), recent reviews that mention ADU or conversion work, and clear written bids. Browse ADU builders by city.

Frequently asked questions

This page is general information, not legal, tax or financial advice. Costs vary by property and builder. Images are AI-generated illustrations. Last updated November 2026.