The Complete San Diego ADU Requirements Guide
If you’re thinking about building an accessory dwelling unit (ADU) in San Diego, it’s worth understanding the requirements before you begin.
ADUs are secondary housing units—like a backyard cottage, converted garage, or in-law apartment—built on the same lot as a primary residence. California law requires cities like San Diego to allow ADUs in all residential zones, and San Diego has adopted additional incentives to encourage construction. As a result, permitting and building an ADU here is relatively streamlined.
Read on to learn everything you need to know about building an ADU in San Diego and how Samara can help.
San Diego ADU regulations at a glance
San Diego reviews ADU applications through a ministerial process—meaning no public hearings or discretionary review—and is required to respond to complete submissions within 60 days. Most permits are approved in three to four months. California law guarantees a set of baseline entitlements for ADUs, and San Diego has adopted additional local standards and bonuses that go beyond those minimums.
Size and lot requirements
San Diego sets clear size limits for ADUs based on type:
- Detached ADUs must be at least 150 square feet and may be up to 1,200 square feet. They may be built up to 16 feet tall by right, or up to 18 feet if the lot is within a half-mile of a major transit stop or on a multifamily property. Up to 20 feet is allowed if the roof pitch matches the primary home.
- Attached ADUs must also be at least 150 square feet and may be up to 1,200 square feet. They may be built up to 25 feet tall or match the zoning height limit, whichever is lower.
- Junior ADUs (JADUs) must be between 150 and 500 square feet and must be created within the existing or proposed single-family home.
All new ADUs must observe front and street-side setbacks per the base zoning. Rear and side setbacks are reduced to 4 feet when the ADU is over 16 feet tall, and may be reduced to 0 feet for single-story ADUs under 16 feet, subject to fire code. Setbacks do not apply to conversions or rebuilds within the footprint of an existing structure.
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Parking requirements
ADUs in San Diego generally do not require any new parking. However, in the Beach Impact Area of the Coastal Overlay Zone, one parking space may be required for a new detached ADU unless the ADU is within half a mile of transit, under 500 square feet, part of the main home, or qualifies for another exemption. No replacement parking is required if a garage or carport is converted. JADUs never require parking.
Tree requirements
If you’re building two or more ADUs (including JADUs), San Diego requires you to plant trees on your lot—at least one tree per property and two trees for every 5,000 square feet of lot area. Trees must be chosen from the city’s approved list and comply with the Land Development Manual.
Zoning eligibility
ADUs are permitted on any lot in San Diego that allows residential use, including all single-family, multifamily, and mixed-use zones. ADUs must be located on a lot with an existing or proposed primary residence. Additional requirements may apply within the Coastal Overlay Zone or Areas of Future Sea Level Rise.
Number of ADUs allowed
On single-family lots, you can build one detached ADU, one conversion ADU within the main house or an existing structure, and one JADU.
On multifamily lots with an existing residential building, California law allows up to eight detached ADUs—or fewer if that would exceed the number of existing units. Inside the primary building, an unlimited number of ADUs may be created from non-habitable spaces such as storage rooms or garages. Up to 25% of the existing unit count may also be converted from habitable space. If the primary building is still in development, up to two detached ADUs are allowed during construction.
San Diego also allows extra ADUs if you rent some of them at affordable rates. If you agree to keep a unit affordable for 10 to 15 years, you can build one bonus ADU in return. Within Sustainable Development Areas (parts of the city close to transit) you can build an unlimited number of bonus ADUs as long as each one is matched with an affordable unit.
Streamline your San Diego ADU
If you’re looking to build an ADU, Samara makes it easy. We handle everything from permits to installation and even offer our own financing. Call us at 650-420-2607 to schedule a 15-minute consultation and discover how simple adding a Backyard ADU can be.
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