ADU vs JADU: What's the Difference? Complete 2025 Comparison Guide

If you're a California homeowner looking to add extra living space to your property, you've probably come across two terms: ADU (Accessory Dwelling Unit) and JADU (Junior Accessory Dwelling Unit). While they sound similar, these two housing options have distinct differences that could significantly impact your building plans, budget, and long-term goals.

In this guide, we'll break down everything you need to know about ADUs vs JADUs to help you make the right choice for your property.

What is an ADU?

An Accessory Dwelling Unit (ADU) is a complete, independent living space located on the same property as a primary residence. ADUs provide all the amenities needed for independent living, including:

• Full kitchen with cooking facilities
• Bathroom with shower/tub, toilet, and sink
• Sleeping area
• Living space
• Separate entrance

ADUs can be:

• Detached - A standalone structure separate from the main house
• Attached - Connected to the main house (like an addition)
• Converted - Created from existing space (garage, basement, attic)

Size: ADUs typically range from 150 to 1,200 square feet, depending on local regulations and whether they're attached or detached.

What is a JADU?

A Junior Accessory Dwelling Unit (JADU) is a smaller, more restricted type of accessory dwelling unit. JADUs are designed to be a compact living space carved out from within an existing single-family home.

Key characteristics of JADUs:

• Maximum 500 square feet
• Must be located entirely within an existing single-family home (including attached garages)
• May share bathroom facilities with the main house (or have its own)
• Requires an efficiency kitchen (small cooking area with basic appliances)
• Must have a separate entrance from the main living area

Think of a JADU as a large studio apartment created within your existing home's footprint.

Key Differences Between ADUs and JADUs

Here's a quick comparison to help you understand the main differences:

Size and Space Requirements

ADU Size Requirements

California law requires local agencies to allow ADUs of at least:

• 850 square feet minimum (or 1,000 sq ft if the ADU has more than one bedroom)
• 1,200 square feet maximum for detached ADUs (without a local ordinance)
• Up to 50% of the primary dwelling for attached ADUs

Some local jurisdictions allow even larger ADUs through more permissive local ordinances.

JADU Size Requirements

JADUs are strictly capped at 500 square feet maximum. There's no minimum size requirement, though the space must be large enough to meet building code standards for habitable space (typically at least 150 sq ft for an efficiency unit).

Location: Where Can You Build?

ADU Location Options

ADUs offer maximum flexibility:

• Detached garage conversion - Transform your existing garage into a standalone unit
• New detached structure - Build a brand-new separate building in your backyard
• Above the garage - Add a second story ADU over your existing garage
• Attached addition - Extend your home with an attached ADU
• Basement or attic conversion - Convert existing interior space
• Accessory structures - Convert sheds, workshops, or other structures

JADU Location Requirements

JADUs are much more limited:

• Must be entirely within the existing single-family home's walls
• Can be created in attached garages (these count as part of the home)
• Cannot be built in detached structures like separate garages or sheds
• Typically created by dividing existing bedrooms, converting a portion of the home, or using an attached garage

Kitchen and Bathroom Requirements

ADU Requirements

An ADU must have complete, independent living facilities:

• Full kitchen: Standard-size appliances, full sink, adequate counter space, storage cabinets
• Full bathroom: Toilet, sink, and bathtub or shower
• All utilities must be fully functional and meet building codes

JADU Requirements

JADUs have more relaxed requirements:

• Efficiency kitchen: Smaller appliances, basic food prep counter, minimal cabinet space - just enough for simple meal preparation
• Bathroom: Can either have its own full bathroom OR share facilities with the main house
• If sharing a bathroom, the JADU must have an interior connection to the main house
• If it has its own bathroom, no interior connection is required

Owner-Occupancy Requirements

ADU Owner-Occupancy

No owner-occupancy requirement. As of January 1, 2024, California eliminated all owner-occupancy requirements for ADUs. You can:

• Rent out both your main house and your ADU
• Live in the ADU and rent out your main house
• Rent out the ADU while living in your main house
• Use the ADU for family members

JADU Owner-Occupancy

Owner-occupancy is required. The property owner must live in either:

• The main house, OR
• The JADU itself

This requirement does NOT apply if the owner is a government agency, land trust, or housing organization.

Construction and Permitting

ADU Permitting Process

• Timeline: Must be approved or denied within 60 days of a complete application
• Review: Ministerial approval (no discretionary review or public hearings)
• Parking: May require up to 1 parking space (or zero spaces in certain locations)
• Setbacks: Typically 4-foot side and rear setbacks for new construction
• Building codes: Must comply with all residential building codes

JADU Permitting Process

• Timeline: Must be approved or denied within 60 days of a complete application
• Review: Ministerial approval (no discretionary review)
• Parking: No parking required (even if converting an attached garage)
• Setbacks: N/A (since it's within existing structure)
• Deed restriction: Requires a recorded deed restriction preventing separate sale

Cost Considerations

ADU Costs

Building an ADU typically costs:

• Garage conversion: $100,000 - $150,000
• Detached new construction: $150,000 - $300,000+
• Attached addition: $150,000 - $250,000

Costs include:

• Construction materials and labor
• Permits and fees
• Utility connections (may require separate connections)
• Impact fees (if over 750 sq ft, charged proportionately)

JADU Costs

Creating a JADU is generally less expensive:

• Typical cost range: $25,000 - $80,000
• Lower cost factors:
• No new structure required
• Can share utilities with main house
• No new utility connections needed
• Exempt from impact fees
• No parking requirements

JADUs are often the most affordable option for adding living space to your property.

Rental Income Potential

ADU Rental Income

ADUs offer strong rental income potential:

• Can be rented as a completely independent unit
• Typically command higher rents (full kitchen and bathroom)
• More attractive to long-term tenants
• Average California ADU rent: $1,500 - $3,500/month (depending on location and size)
• Minimum rental term: 30 days or longer

JADU Rental Income

JADUs offer more modest rental income:

• Smaller size = lower rent
• May be less appealing without full kitchen/bathroom
• Best suited for students, single professionals, or elderly family members
• Average California JADU rent: $800 - $1,800/month
• Minimum rental term: 30 days or longer

Which Should You Choose?

Choose an ADU if:

• You want maximum rental income potential
• You have available yard space for a detached structure
• You want complete independence between units
• You might want to sell the property later (ADUs can be sold separately in some cases)
• You're converting a detached garage or building new construction
• You have the budget for a larger project

Choose a JADU if:

• You have limited outdoor space
• You want a more affordable option
• You're comfortable with owner-occupancy requirements
• You want to keep family members close while maintaining some privacy
• You have existing interior space you can convert
• You want to minimize construction complexity
• You primarily want the unit for family use rather than maximum rental income

Can You Have Both?

Yes! California law allows you to build both an ADU and a JADU on the same single-family property. For example, you could:

• Create a JADU within your main house (up to 500 sq ft)
• Build a detached ADU in your backyard (up to 1,200 sq ft)
• Convert your garage into an ADU
• Build an attached ADU addition

This combination gives you maximum flexibility and income potential while utilizing different parts of your property.

Common Misconceptions

Myth: JADUs are just small ADUs

Reality: JADUs have unique requirements (owner-occupancy, must be within the main house, can share bathrooms) that make them fundamentally different from ADUs.

Myth: You need a large lot for an ADU

Reality: Even small lots can accommodate ADUs through garage conversions or attached additions. There are no minimum lot size requirements.

Myth: You can't build an ADU if you have HOA restrictions

Reality: California law (Civil Code § 4751) makes HOA restrictions that prohibit ADUs void and unenforceable. HOAs can only impose reasonable design standards.

Myth: JADUs don't need permits

Reality: All JADUs require building permits and must meet building codes, just like ADUs.

Recent Law Changes (2025 Update)

California continues to make it easier to build both ADUs and JADUs:

• No owner-occupancy requirement for ADUs (eliminated January 1, 2024)
• Separate sale allowed for ADUs under certain conditions with local ordinance
• Unpermitted ADU amnesty extended to units built before January 1, 2020
• Pre-approved ADU plans required by local agencies as of January 1, 2025
• 60-day approval timeline strictly enforced for both ADUs and JADUs

Next Steps

Ready to move forward? Here's what to do:

1. Assess your property - Determine what space you have available 2. Check local requirements - Contact your city or county planning department 3. Set your budget - Determine how much you can invest 4. Define your goals - Rental income, family use, or increasing property value? 5. Consult with professionals - Architects, contractors, and ADU specialists 6. Submit your application - Work with your local permitting agency

Both ADUs and JADUs offer valuable opportunities to add housing and generate income on your California property. The right choice depends on your specific property, budget, and goals.

Frequently Asked Questions

*This article reflects California ADU and JADU laws as of January 2025. Laws and local requirements may vary by jurisdiction. Always consult with your local planning department and relevant professionals before beginning any construction project.*