What is a JADU?
A JADU, or junior accessory dwelling unit, is a smaller secondary home created within the existing walls of your primary residence. Unlike a full ADU, a JADU does not expand the footprint of your home—it must fit inside the structure that already exists.
A JADU has a maximum of 500 square feet of interior livable space as of January 1, 2026. This is measured as interior livable space, not total footprint. The unit must have a separate entrance from the primary home, accessible from the exterior.
JADUs may share a bathroom with the primary home in some cases, depending on local requirements. However, the JADU must have its own kitchen or efficiency kitchen (a smaller cooking and food preparation area).
JADUs are designed to create flexible housing for family members, provide rental income, or make better use of existing residential space without the cost and complexity of a full ADU project.
JADU vs full ADU
JADUs and full ADUs serve similar purposes but have key differences in design, rules, and requirements:
Size
JADU
Max 500 sq ft interior livable space
Full ADU
Larger; fewer strict size restrictions
Location
JADU
Must be within existing walls of primary home
Full ADU
Can be detached, attached, or converted anywhere on lot
Kitchen
JADU
Efficiency kitchen allowed (smaller, reduced counter/storage)
Full ADU
Full, independent kitchen required
Bathroom
JADU
May share bathroom with primary home in some cases
Full ADU
Must have independent bathroom
Owner occupancy
JADU
Required: owner must occupy either primary home or JADU
Full ADU
Generally not required (varies by local law)
Cost
JADU
Often cheaper since it uses existing structure
Full ADU
May be more expensive depending on type
Size limits
As of January 1, 2026, a JADU is limited to a maximum of 500 square feet of interior livable space. This definition was revised by the California Housing and Community Development (HCD) Department in their 2026 addendum to the ADU Handbook.
The key measurement is interior livable space, not total footprint. This means you measure the usable living area inside the unit, not including exterior walls, mechanical spaces, or non-livable areas.
Because a JADU must fit within existing walls, the 500-square-foot limit is the binding constraint. You cannot expand the primary home to create a larger JADU.
Owner occupancy requirements
One of the most important differences between a JADU and a full ADU is the owner occupancy requirement. JADUs require owner occupancy in either the primary home or the JADU itself.
This means that if you rent out both the primary home and the JADU to separate tenants, you may not comply with state and local JADU rules. At least one of the two units must be owned and occupied by the property owner.
In practice, this requirement is enforced through a deed restriction, which is typically recorded at the county assessor or county recorder's office. The deed restriction formalizes the owner-occupancy requirement and remains with the property.
Before moving forward with a JADU, make sure you understand whether this requirement aligns with your long-term housing plans. If you anticipate renting out both units to different tenants in the future, a full ADU may be a better fit for your property.
Kitchen requirements
JADUs are allowed to have an efficiency kitchen, which is smaller and simpler than a full kitchen required for a standard ADU. An efficiency kitchen may include:
- Small cooking facilities (electric or gas cooktop, microwave, or compact range)
- Sink with hot and cold water supply
- Food preparation counter space
- Limited cabinet or storage space
The efficiency kitchen approach is one reason JADUs are often more affordable to build than full ADUs—the smaller kitchen takes up less space and is less expensive to install.
As always, check your local building codes and your city's JADU guidelines to confirm what kitchen equipment and configuration your jurisdiction will permit.
When a JADU makes sense
A JADU may be the right choice for your property if:
- You have unused interior space (bonus room, large bedroom, wing of the home)
- You want lower construction costs compared to a detached ADU
- You are comfortable with the owner-occupancy requirement
- You don't need a full-sized second unit—500 square feet is sufficient for your needs
- You want to create flexible housing for a family member
- Your lot size or zoning makes a separate ADU structure difficult or impossible
- You want to preserve backyard or sideyard space
Conversely, if you need a larger unit, want to rent out both homes to different tenants, or lack usable interior space, a full ADU may be a better fit.
Common JADU paths
Most homeowners explore one of these conversion approaches when building a JADU:
Converting a bedroom or bonus room
Adding walls, plumbing, and kitchen facilities to an existing bedroom or bonus room. This is often the most straightforward path.
Converting part of a garage
Using the space above or within an existing garage structure (within existing walls). Requires adding living facilities while meeting fire safety and egress requirements.
Converting a master suite or home wing
Separating and enclosing a portion of the main home, such as a master suite or entire wing with multiple rooms. Requires careful attention to utilities, entrances, and separation.
All JADU conversions require a separate entrance that is accessible from the exterior. This is a key requirement and often shapes the design approach.
What to check with your city
Before starting a JADU project, verify these items with your local planning and building departments:
Local JADU implementation
Does your city permit JADUs? Some cities may not yet have local JADU rules, or may have specific requirements that differ from state law.
Fire safety requirements
Fire codes may require specific egress windows, fire-rated walls, or sprinkler systems depending on the size and location of the JADU.
Plumbing and mechanical separation
Check if the JADU must have completely separate mechanical systems from the primary home, or if systems can be shared.
Recording requirements for deed restriction
Understand how and where the owner-occupancy deed restriction must be recorded, and what language your city requires.
Parking requirements
Some cities may impose parking requirements for JADUs; others may waive them. Clarify this early.
Local design or architectural standards
Some jurisdictions have additional local standards for exterior appearance, window treatments, or other design features.
Recommended next steps
If you are considering a JADU for your property, here are the resources to explore next:
This page is for general educational purposes only. California JADU law, city implementation, and code requirements can change. Always verify project-specific requirements with the relevant planning department, building department, and qualified professionals.