ADU laws in San Diego let you add one standard accessory dwelling unit of up to 1,200 square feet and one 500-square-foot junior ADU on a single-family lot, with four-foot setbacks, no parking requirement near transit, no owner-occupancy mandate for standard units, and a flat ban on renting any ADU for stays under 30 days. The rules sit at the intersection of state law and the San Diego Municipal Code, and recent changes have removed most of the discretionary hurdles that used to slow these projects.
The Three Types of ADUs and Their Size Caps
San Diego recognizes three categories. A detached ADU is a standalone building. An attached ADU shares at least one wall with the main house. A junior ADU, or JADU, is carved out of space inside an existing or proposed single-family home.
Both attached and detached ADUs are capped at 1,200 square feet under the San Diego Municipal Code.1City of San Diego. San Diego Municipal Code Chapter 14, Article 1, Division 3 – Accessory Dwelling Units and Junior Accessory Dwelling Units For attached units, state law also guarantees that the city must allow at least 800 square feet even on a small home, so the practical range is 800 to 1,200. Detached units can reach 1,200 square feet regardless of how big the main house is.
JADUs are limited to 500 square feet and must sit within the walls of an existing or proposed single-family home. A JADU can have an efficiency kitchen with a sink, cooking appliance, and counter, and it is allowed to share a bathroom with the main house instead of adding its own. Converting a bedroom or attached garage into a JADU is usually the cheapest way to add a legal rental, since you are reusing existing permitted space rather than building new.
Conversions in general carry lighter construction obligations than ground-up builds. A new detached ADU has to meet current foundation, structural, and energy codes in full. A permitted garage being converted already has a shell, which can take several code triggers off the table.
How Many Units You Can Build
On a single-family lot, the baseline is one standard ADU plus one JADU.2City of San Diego. Accessory Dwelling Units The JADU has to be inside the single-family home; the standard ADU can be attached or detached. Multifamily lots are allowed at least one ADU, with more possible depending on the number of existing apartments and whether there is non-habitable space available to convert.
If you are willing to deed-restrict units as affordable, the ADU Bonus Program lets you go further. More on that below.
Setbacks, Height, and Parking
New ADU construction gets a four-foot setback from the rear and side property lines.1City of San Diego. San Diego Municipal Code Chapter 14, Article 1, Division 3 – Accessory Dwelling Units and Junior Accessory Dwelling Units That drops to zero when you convert an existing permitted structure like a garage, or when you build a new unit that stays at or below 800 square feet and 16 feet in height. On a tight lot, that zero-setback allowance can be the difference between a buildable project and no project.
Height limits depend on where the lot sits relative to transit. Properties in Transit Priority Areas, generally within a half-mile of a major transit stop, can go taller, with state law allowing detached ADUs up to 25 feet in certain configurations. Outside those areas, caps for a detached single-story unit typically land between 16 and 18 feet. An attached ADU follows the height rules of the main house.
Parking requirements have been stripped out across most of the city. If your property is within a half-mile of a major transit stop or along a high-quality transit corridor, no ADU parking is required. Converting a garage or carport into an ADU does not trigger replacement parking even if that garage was counting toward the home’s original parking obligation. Outside transit-rich areas, the general rule is one off-street space per ADU, with some exceptions in historic districts.
When Fire Sprinklers Are Required
The baseline rule under state law is that if the primary home has no sprinklers, a standard ADU does not need them either, provided the unit meets other health and safety standards.3City of San Diego Official Website. Sprinkler Requirements for Accessory Dwelling Units If the primary home already has sprinklers, an attached ADU must have them.
That exemption disappears for affordable ADUs and bonus ADUs built under the city’s ADU Bonus Program. Those units need an automatic sprinkler system whether or not the primary home has one.3City of San Diego Official Website. Sprinkler Requirements for Accessory Dwelling Units Properties in Very High Fire Hazard Severity Zones may face additional fire-hardening requirements beyond sprinklers.
On multifamily lots, the “primary dwelling” is the entire building rather than one apartment. If the building has sprinklers, an attached ADU converted from existing space in that building will need them too.
The ADU Bonus Program
San Diego’s ADU Bonus Program lets homeowners add extra market-rate ADUs in exchange for building deed-restricted affordable units. The affordability restriction lasts 15 years and must serve very-low-, low-, or moderate-income households.2City of San Diego. Accessory Dwelling Units
Inside Transit Priority Areas, there is no cap on total units: for every affordable ADU you build, you earn one market-rate bonus ADU. Outside those areas, the program allows a single additional pair, one affordable and one market-rate, on top of the baseline units. Bonus projects get ministerial approval with no public hearings, parking is waived for the bonus units, and permitting fees are reduced.
The deed restriction follows the property through resale, and the income-restricted rent will be well below market. For a homeowner with the lot space and the appetite for the trade, the program is the fastest route to maximizing the number of rentable doors.
Applying for a Permit
The Development Services Department handles ADU permits through an online portal, and you need to create an account to submit.4City of San Diego. Development Services Your package should include a site plan showing the property with existing structures and the proposed ADU dimensions, floor plans identifying the kitchen, bathroom, and sleeping areas, and elevation drawings showing exterior appearance. The general application form collects ownership and project information.5City of San Diego Development Services. DS-3032 – General Application
Once submitted, the city routes the project through zoning, building, and utility reviews at the same time. Staff can issue correction requests, and you resubmit revised plans through the portal.
San Diego also accepts pre-approved ADU building plans that have already been vetted for code compliance.2City of San Diego. Accessory Dwelling Units Choosing a standard or permit-ready plan can cut weeks off review, since the building-design questions are already answered; you still need a site-specific application showing how the plan fits your lot.
After plan approval, the city invoices permit and impact fees. You pay through the portal, and the permit issues on payment. State law exempts ADUs under 750 square feet from most local impact fees, which can save thousands on a smaller unit.
Inspections and Final Approval
During construction, the city inspects at the foundation, framing, electrical, plumbing, and final stages. Each one has to pass before the next phase of work can start. Pushing past an inspection without sign-off risks a stop-work order and fines.
San Diego does not issue a formal Certificate of Occupancy for single-dwelling units, duplexes, or townhomes, and most ADUs fall into those categories.6City of San Diego Official Website. Certificate of Occupancy Passing the final inspection on the building permit and all associated permits is your authorization to occupy and rent. Keep a copy of the finaled permit; a future buyer, lender, or tenant may ask to see proof the ADU was legally built.
Rental and Owner-Occupancy Rules
ADUs and JADUs cannot be used as short-term vacation rentals. Under state law, any ADU permitted on or after January 1, 2020, cannot be rented for stays shorter than 30 consecutive days. San Diego enforces this alongside its broader short-term rental licensing ordinance, and violations can bring fines and permit problems.
Standard ADUs carry no owner-occupancy requirement. You do not have to live on the property to rent the ADU, and you do not have to live in the ADU to rent the main house. State law permanently eliminated that mandate for standard units.
JADUs are the exception. You have to live on the property, in either the primary home or the JADU itself, as a condition of having the unit.7California Department of Housing and Community Development. Accessory Dwelling Unit Handbook That requirement is recorded as a deed restriction, so it binds future owners too. If you sell, the next owner either lives on-site or stops renting the JADU separately. If you want to rent without living on the property, a standard ADU is the right choice.
Selling an ADU separately from the main home is possible under certain state-law programs, but the eligible configurations continue to shift. If separate conveyance matters to your plans, check with the city’s planning department and a real estate attorney before you design around it.