Detached ADU · City of San Diego
Detached ADUs in San Diego
A detached ADU is a separate home in your yard, with its own kitchen and bathroom. In the City of San Diego it can be 150 to 1,200 square feet and up to two stories on a single-family lot. You can rent it out for 31 days or longer.
BHI Builders designs, permits and builds detached ADUs, along with attached ADUs, garage conversions and junior ADUs, across San Diego County's 19 permit authorities, as one team, under California contractor license 738313, issued in 1997.
- 1997Licensed in California sinceCheck the license
- 111Permits on the public record, 2000 to 2025See the projects
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Right for your lot when
You have yard to spare, want the most privacy and the strongest rent, or want two stories and a view.
The wrong choice when
The yard is small or steep, or the sewer and power are far from where it would sit: a new foundation and new utility runs are most of the work of a detached ADU, and a garage conversion or an attached ADU may serve you better.
On the call we tell you which type fits your lot, including if the answer is none.
The rules for a detached ADU
| Rule | What applies |
|---|---|
| Size | 150 to 1,200 square feet of floor area. A garage or carport under the ADU doesn't count toward the 1,200. |
| Height | Up to two stories on a lot zoned for one home, within the zone's overall height limit: 30 feet in the RS-1-1 to RS-1-7 zones, 35 feet in RS-1-8 to RS-1-14, and never over 30 feet west of where Interstate 5 ran in 1971. State law guarantees at least 16 feet anywhere. |
| Side and rear setbacks | None for an ADU 16 feet tall or less. Taller than that, 4 feet (or the zone's setback, if less) where it borders a residential lot. In a Very High Fire Hazard Severity Zone, the only kind on the City's fire map, 4 feet at any height, and more in a Brush Management Zone if the Fire Code Official asks. |
| Front yard | The zone's front setback applies, but one ADU of 800 square feet or less can sit in the front yard when it is the only attached or detached ADU on the lot. |
| Over a garage | Allowed. On a lot zoned for one home it can be two stories in all, and the garage beneath doesn't count toward the ADU's size. |
| Parking | None in most of the City. In the Beach Impact Area outside a transit priority area, a new detached ADU over 500 square feet needs one space unless it is in a designated historical district or a residential permit parking district, or a car share vehicle is within a block, and a garage or carport it replaces there must be replaced. |
| Rental term | 31 days or longer. Short-term vacation rentals aren't allowed. |
| Owner on site | Not required. The owner doesn't have to live on the property. |
| Fees | State law bars impact fees on an ADU of 750 square feet or less. The City waives its development impact fees on the first two ADUs on a lot at any size. School fees apply from 500 square feet, and the City's General Plan Maintenance Fee applies to every ADU. |
| Selling it | The City lets an owner split off an ADU as a condominium and sell it, with conditions, outside the Coastal Zone. A rent-restricted or Housing Commission-assisted ADU can't be sold while its restriction lasts, and a bonus project needs the Housing Commission's consent. |
| Heating | Under the 2025 Energy Code, a new ADU's heating and cooling is a heat pump, unless the design meets the energy budget another way. |
Outside the City of San Diego, your city or the County sets these rules within state law. Who issues my permit?
What a detached ADU costs
Our calculator's planning range at a plain spec: about 800 square feet, standard finishes, a flat lot and easy access. Your size, site and finishes move it.
$318,040 to $428,632
Questions about detached ADUs
How big can it be?
Up to 1,200 square feet in the City of San Diego, and at least 150. Outside the City, your city sets the limit, but state law guarantees room for at least 850 square feet, or 1,000 with more than one bedroom.
How tall?
Up to two stories on a single-family lot, within your zone's overall height limit: 30 feet in the RS-1-1 to RS-1-7 zones, 35 in RS-1-8 to RS-1-14, and never over 30 feet west of where Interstate 5 ran in 1971. Anywhere in California, a city has to allow at least 16 feet.
Can it go in my front yard?
Sometimes. The zone's front setback usually applies, but one ADU of 800 square feet or less can sit in the front yard when it's the only attached or detached ADU on the lot. We check where it fits on the first visit.
Can I build over my garage?
Yes. An ADU can sit on top of a detached garage, two stories in all on a lot zoned for one home. The garage beneath doesn't count toward the ADU's size, and the Energy Code treats the ADU as an addition, so solar panels aren't required.
Do I need parking?
Not in most of the City. Near the beach, in the Beach Impact Area outside a transit priority area, a new detached ADU over 500 square feet needs one space unless an exception applies, and a garage or carport it replaces there must be replaced. We check which applies to your lot.
Do I pay impact fees?
State law bars impact fees on an ADU of 750 square feet or less, and the City of San Diego waives its development impact fees on the first two ADUs on a lot at any size. School fees from 500 square feet, the City's General Plan Maintenance Fee, and water and sewer capacity charges sized to the ADU still apply.
Talk to us about your lot.
Tell us where it is and what you want the ADU to do. We'll walk it with you and tell you what fits.
