Most homeowners have heard of an ADU. Far fewer have heard of its smaller sibling, the junior accessory dwelling unit, even though for some households it is the better answer. A JADU is a unit of no more than 500 square feet carved out of the existing house, with its own entrance and a small kitchen, that can be rented or used by family. It does not need a new foundation, a new roof or a trench for utilities, and that is why it is the least expensive permitted unit California allows.
This guide explains what a JADU is, what the 2026 rules require, what drives its cost, and when it makes more sense than a full ADU. It is written from the point of view of a design-build team that builds both, so we will be direct about the trade-offs.
What a JADU is, in plain terms
California defines a junior accessory dwelling unit as "a unit that is no more than 500 square feet of interior livable space in size and contained entirely within a single-family residence." (Government Code section 66313) Three words in that definition do most of the work.
- Within. A JADU is built inside the walls of the existing or proposed house. An attached garage counts as part of the house for this purpose, so a JADU can be carved out of it. A detached garage or a new backyard structure cannot be a JADU; those are ADUs.
- 500 square feet. That is the ceiling on interior livable space. A JADU is a studio or a one-bedroom, not a family home.
- Junior. It is a category of its own, with its own rules on kitchens, entrances, bathrooms and owner-occupancy, and with one important advantage: state law lets a single-family lot have one ADU and one JADU, so a JADU can be added on top of an ADU rather than instead of one.
The typical JADU in Los Angeles is a converted bedroom with an adjacent bath, a section of an attached garage, or a wing of the house with its own door to the side yard.
The 2026 rules, in one place
The JADU rules were renumbered in 2024 and changed again for 2026. Here is what applies now, with the statute so you can read it yourself.
| Rule | What the law says |
|---|---|
| Size | No more than 500 sq ft of interior livable space |
| Location | Entirely within the single-family residence; an attached garage counts as within |
| How many | One JADU per lot; may be combined with one ADU on the same lot |
| Entrance | A separate entrance from the main entrance of the house |
| Kitchen | An efficiency kitchen: a cooking appliance, a food-preparation counter and storage cabinets of reasonable size |
| Bathroom | May be its own, or shared with the main house |
| Owner-occupancy | Required only if the JADU shares a bathroom with the main house; not required if the JADU has its own bathroom, or if the owner is a government agency, land trust or housing organization |
| Parking | No additional parking may be required |
| Sale | Cannot be sold separately from the house; a deed restriction is recorded |
| Rental term | Longer than 30 days |
| Review | Ministerial, no hearing; approved or denied within 60 days of a complete application |
| Impact fees | Exempt for a JADU of 500 sq ft or less, under state law effective 2026 |
| Fire sprinklers | Not required if the main house does not require them |
The owner-occupancy line is the one that changed. Until this year, an owner had to live on the property to have a JADU at all. Under AB 1154, chaptered in October 2025, the requirement now applies only when the JADU shares sanitation facilities with the main house. Give the unit its own bathroom and the owner-occupancy requirement falls away. (Government Code section 66333) For an owner who may move out and rent the whole property one day, that single design decision matters.
What drives the cost
We scope every JADU individually and we do not publish a JADU price range, because the spread between a bedroom that already has a bathroom next door and a garage bay that has nothing is too wide for one number to be honest. What we can tell you is where the money goes, in rough order.
The bathroom
If the JADU can use an existing bathroom, either its own or one shared with the house, the project is mostly finish work. If a bathroom has to be added, the plumbing, waterproofing and tile make it the largest single cost, the same as any bathroom remodel in Los Angeles. Given the owner-occupancy rule above, a private bathroom is also what makes the unit fully rentable without you living there, so it is usually worth it when the plumbing is reachable.
The efficiency kitchen
State law requires a cooking appliance, a counter for food preparation and storage cabinets of reasonable size. It does not require a full range or a dishwasher. A compact induction cooktop, a counter-depth refrigerator, a sink and a run of cabinets meet the standard and keep the electrical and plumbing modest. The sink and the cooktop still need water, drain and circuits, which is where a JADU in a garage bay costs more than one in a bedroom.
The entrance
A separate entrance from the main entrance means a new exterior door, sometimes a short path and a light. In a bedroom on a side yard this is a door where a window was. In an attached garage it usually means removing or partly removing the garage door and framing a wall with a door in it.
Electrical and comfort
Enough circuits for the kitchen, a dedicated heating and cooling solution, often a mini-split, and sound insulation in the wall shared with the house. Some older homes need panel work before any of this.
Design and permits
Drawings, energy-code compliance, plan check and inspections. A JADU is reviewed ministerially within 60 days of a complete application, and it is exempt from impact fees, so the permit path is usually the simplest of any unit type.
Where it gets expensive
A JADU carved from an attached garage that has a thin, sloped slab, no insulation and no plumbing is the costly version: it needs much of the work described in our garage conversion versus detached ADU comparison, minus the separate utilities. A JADU made from a bedroom and bath in a home with a reasonable panel is the inexpensive version. The site visit tells us which one you have.
How long it takes
Because the structure, roof and usually the bathroom already exist, a JADU carved from existing space often runs six to ten weeks of construction, in line with our other conversions of existing space. Adding a bathroom or reworking a garage bay adds to that. The design phase, in which every material is chosen before work starts, comes before it, and the city's 60-day review clock runs from a complete application.
When a JADU makes sense
- You need a home for a family member, close but separate. A parent who wants a door of their own, an adult child, a caregiver. The JADU keeps them within the house without turning the house into a shared apartment.
- You want rental income from a small unit without a large project. A studio with its own bathroom and entrance rents to one person and costs a fraction of a detached ADU.
- Your lot has no room for an ADU, or the setbacks, slope or utilities make a detached unit impractical.
- You already have or plan an ADU and want a second unit. State law allows one of each on a single-family lot; many owners build the ADU for income and the JADU for family, or the reverse.
- You want the lowest-cost permitted unit with the simplest review. No impact fees, no parking requirement, no hearing.
When it does not
- You want full independence for a tenant. A JADU shares a roof and usually a wall with your home. A detached ADU rents like a small house and earns accordingly.
- The house is small. Taking 500 square feet out of a 1,200-square-foot home leaves a 700-square-foot home.
- You plan to move out and the unit would share your bathroom. That triggers owner-occupancy. Give it a bathroom or build an ADU instead.
- Privacy and noise matter more than cost. The shared wall can be insulated; it cannot be removed.
Common mistakes
- Calling a bedroom with a hot plate a JADU. Without the permit, the deed restriction, the separate entrance and a compliant efficiency kitchen, it is not a JADU. It cannot be legally rented and it complicates insurance and resale.
- Skipping the bathroom decision. Whether the unit has its own bathroom decides both the cost and whether you must live on the property. Decide it in design.
- Forgetting egress and ventilation. A sleeping area needs a compliant egress window or door and proper ventilation; the kitchen needs an exhaust path. These are inspection items, not options.
- Ignoring the shared wall. Sound insulation and a solid-core door are inexpensive during construction and disruptive afterward.
- Assuming the JADU rules are the ADU rules. They overlap but they are not the same. The 500 sq ft cap, the location inside the house, the deed restriction and the owner-occupancy rule are JADU-specific.
How we approach a JADU
- Discovery. A site visit to look at where the unit could sit, where the plumbing is, what the panel can carry, and whether the lot could also take a full ADU now or later.
- Design. A layout that meets the size, entrance, kitchen and egress rules, a decision on the bathroom, and every material selected before construction.
- Permits. The JADU application, the deed restriction, and energy-code compliance, handled with the city.
- Construction. Typically weeks, not months, with a dedicated project manager.
- Walkthrough. A permitted, inspected unit with the paperwork that makes it legal to rent.
Our ADU page covers all four unit types, our ADU cost guide explains what is inside the numbers for the larger units, and our guide to financing an ADU covers how families pay for them. Finished units are in our ADU projects.
A realistic next step
If you are wondering whether a corner of your house could become a legal, rentable unit, the answer is on a site visit, not in an article. Request a consultation and we will walk the house with you, tell you whether a JADU, an ADU or both fit, and give you a preliminary range for the version that makes sense.