Home/ADU Construction/Junior ADU (JADU)
Junior ADUs · San Diego County
A junior accessory dwelling unit turns up to 500 square feet of your existing house into a separate living space, with its own entrance and an efficiency kitchen. We design and build JADUs to state law and your city’s rules, from the first measurement through final inspection.
A JADU is the smallest type of ADU under California law. Instead of building a new structure in the yard, it carves a self-contained space out of rooms you already have: a spare bedroom suite, part of a larger floor plan, or an attached garage. Because the walls, roof and foundation are already there, the work is mostly interior.
State law defines the rules in Government Code §66333, and the City of San Diego applies them through Information Bulletin 400. Other cities in the county, and the County itself for unincorporated areas, run their own permit offices and can add local requirements. Sheiner Construction (CSLB License #1083621) confirms which rules apply to your address before any design work starts.
These are the requirements we design around on every JADU. Each one shapes the floor plan, so we settle them first.
No more than 500 square feet of interior living space under state law. The City of San Diego sets the range at 150 to 500 square feet.
The unit must sit within the walls of the existing or proposed single-family home. California counts an attached garage as part of the house for this purpose.
A JADU needs its own exterior entry. If it doesn’t have its own bathroom, state law also requires interior access to the main house.
A cooking facility with appliances, a food preparation counter and storage cabinets, sized to the space rather than a full kitchen.
The JADU can have its own bathroom or share one with the main house. That choice affects owner-occupancy rules and the plumbing scope.
State law requires a recorded deed restriction so the JADU can’t be sold separately from the house, and the City of San Diego requires a Junior Unit Agreement before the permit is issued.
The City of San Diego is stricter than state law in one important way: an owner must live on the property wherever a JADU exists, in the main house, an ADU or the JADU itself, with limited exemptions for agencies and housing organizations. State law only requires that when the JADU shares a bathroom with the main house.
The City allows a single-dwelling lot to have a primary home, one attached or detached ADU, one converted ADU and one JADU. A JADU needs fire sprinklers only if the primary home already has them; where it doesn’t, a fire-rated wall may be required between the units. State law calls for JADU rentals to be longer than 30 days; we confirm how your city applies that.
Fees are part of the planning too. The City’s Information Bulletin 400 lists school fees and the General Plan Maintenance Fee as applying to ADUs and JADUs. We confirm the current fee picture for your parcel at plan check rather than estimating it up front.
Rules change with each code cycle and local ordinance update. The 2025 California Building Standards Code took effect on January 1, 2026. We confirm current requirements with your building department before design decisions are locked.
Most JADU work happens inside an existing shell, so the sequence is about planning the space and the systems.
We measure the space, confirm it can stay within the size limit, and check the electrical panel, plumbing routes and entry location. We also confirm your jurisdiction’s owner-occupancy and fee rules.
Interior design and construction drawings are developed together, including the kitchen layout, bathroom choice, fire separation and energy compliance. We submit the permit package and prepare the Junior Unit Agreement and deed restriction where required.
Framing, rough plumbing, electrical and mechanical work are inspected before walls close. Finishes follow, and the final inspection closes the permit, creating the legal record of the new unit.
We’ll look at the space, the entry options and your local rules, and tell you what a JADU in your home would involve before drawings are ordered.
Sheiner Construction · CSLB License #1083621, Class B General Building · San Diego, California
We build JADUs, ADUs and conversions across San Diego County, in the City of San Diego and in East County, South Bay and North County cities, each under its own building department’s rules.
