San Diego County has updated its ADU ordinance to comply with new state laws. Below are the up-to-date requirements for permitting an ADU in San Diego County.
Updated May 03, 2023
San Diego County
San Diego County is one of the most desirable places to live in California. The weather is amazing and there are many things to do. One of the best things about living in San Diego County is the ability to build an Accessory Dwelling Unit.
ADUs are small living spaces that are attached to or detached from a single-family home. Building an ADU in San Diego County is a great way to increase the value of your home while also earning rental income, or to create housing for a family member. If you are hoping to build an ADU in the City of San Diego, we have a separate guide dedicated to City of San Diego regulations.
General ADU requirements
The requirements of your project would change based on the type of ADU you’re building. Detached, attached, conversion and Junior ADUs (JADUs) can be built wherever permitted, as long as they match the design of the primary dwelling and keep roof forms, materials, and other architectural details similar.
ADUs must be equipped for independent living and have permanent facilities for:
Exterior access that is separate from the primary dwelling
ADU kitchens must also have:
A sink with running water
Countertops and cabinetry
A permanent range/cooktop
While most of these requirements also apply to JADUs, they may share bathroom/sanitation facilities with the primary dwelling, in which case they must have an interior access point.
Fees typically make up less than 10% of the cost of your project and exact values depend on its scope.
Plan check fees include the cost of assembling and printing your ADU plans before they are submitted for approval. San Diego County requires the in-person submission of plans, which might cost a bit of time and money.
Building permit fees are paid to review whether your project is safe, legal, and possible. Your fee includes a base rate of approximately $1,500 and a cost per sq. ft.
Impact fees are required for proposed and new developments to cover the cost of public services provided by the government. Impact fees are not applicable for ADUs under 750 sq. ft., but if your ADU is larger than 750 sq. ft., you’d have to pay an amount proportional to the floor area of your ADU. You’d also need to get a soil report if your ADU is larger than 500 sq. ft.
Some areas in San Diego, like Cottonwood, Jacumba, and Pine Valley, are not governed by a specific local municipal corporation. These are known as unincorporated areas and, in some cases, benefit from the following fee waivers:
Building permit fees
Onsite wastewater fees
Development impact fees
Traffic impact fees
These waivers can save you between $10,000-$15,000 on permit costs and are valid through January 2024. Aside from the above, you can expect to pay the following fees:
All properties zoned for single-family and multi-family use may be eligible to build ADUs.
Number of units
In San Diego County, a single-family home can have one ADU and/or one Junior ADU (JADU).
Lots zoned for multi-family use with an existing multi-family complex may add two detached ADUs. If you have a multi-family home on a lot that is only zoned for single-family dwellings (SFDs), you may build one ADU.
If you have multiple SFDs on a lot that is only zoned for one SFD, you may build one ADU. JADUs aren’t permitted in such cases.
The number of conversion ADUs allowed is up to 25% of the number of multi-family units on your property. For example, a dwelling with four units may add two detached ADUs and one conversion ADU.
Across all ADU types, the minimum size allowed is 150 sq. ft., but the upper limit depends on whether your ADU is detached from or attached to your main dwelling.
Attached ADUs may be up to 1,200 sq. ft. or 50% of the floor area of your primary dwelling, whichever is larger. A detached ADU can be up to 1,200 sq. ft. no matter the size of the primary dwelling.
A JADU cannot exceed 500 sq. ft. and must be completely contained within the primary dwelling. Conversion ADUs, like the conversion of a garage or basement into a livable area, are also contained within the primary dwelling and do not add floor area to your home.
The County of San Diego restricts the height of detached ADUs to between 24 ft. and 30 ft. and two stories. You may not stack ADUs on top of one another or affix roof decks.
Attached ADUs should follow the setback regulations that apply to the main dwelling.
All newly constructed detached ADUs must follow the following guidelines:
They should have a front yard, side, and rear setbacks of 4 ft. from the property line
Corner lot ADUs should maintain exterior side yard setbacks of at least 4 ft. from the edge of the easement/street/property line
ADUs that are 800 sq. ft. or smaller may encroach into the front yard setbacks but this is up to the County’s discretion—zero lot lines won’t be allowed if there is space to push back from the property line
Conversion ADUs don’t require additional setbacks assuming all fire and safety regulations are met
ADUs built above garages and two-story ADUs must maintain side and rear setbacks of 5 ft. Existing backyard and side yard structures should maintain distances of 6 ft. between structures and 4 ft. from eave to eave.
You don’t need to install fire sprinklers in your ADU if it wasn’t required of your primary dwelling.
One parking space can be allotted for an ADU. It can be located within setbacks and in an existing driveway as tandem parking. Parking spaces don’t need to be replaced if they are demolished to build an ADU or converted into an ADU.
A parking space is not required for an ADU if:
It is located within a one-half mile distance from public transport or one block of a car-share area
It is within an architecturally and historically significant district
It is part of an existing primary residence or accessory structure
It is located within one block of a car-share vehicle
It is in an area where on-street parking permits are required, but not offered to the occupant of the ADU
Usually, owners are only expected to live on-site if a JADU is built. Owners would need to occupy one of the dwellings.
You may not sell an ADU separately from the main dwelling; if you want to sell, the lot has to be subdivided into separate lots for each residential unit.
In addition to providing a great return on investment, ADUs can also serve as a great source of additional income. However, while long-term rentals are permitted, short-term ADU rentals under a period of 30 days are not allowed in the County of San Diego. Depending on its neighborhood and the number of bedrooms your ADU has, you may be able to earn thousands in monthly rental income.
Do you have a utility easement over your property? Are you eligible for fee waivers? Reach out to us, and we’ll help you build a custom ADU to fit your unique property characteristics and local regulations!
How much does it cost to add an ADU in San Diego County?
Depending on the size of your ADU and a number of property factors, your total project cost can range upwards of $100,000. Construction makes up 90% of the cost of your project and hinges on the cost per sq. ft. (which can range between $300-$500). Fees should also be considered and, depending on the scope of your project, can cost you between $9,000-$15,000.
How long does it take to permit an ADU in San Diego County?
Typically, it can take anywhere between 6 months and a year to get a building permit in San Diego County.
How tall can an ADU be in San Diego County?
Detached ADUs may be between 24 ft. and 30 ft. tall, while attached ADUs are contained within the main dwelling.
How close to the property line can I build an ADU in San Diego County?
Your ADU should maintain front, side, and rear setbacks of 4 ft. This means you can build up to 4 ft. from your property line.
Can you convert a garage to ADU in San Diego County?
Yes! Conversion projects are allowed. Conversion ADUs don’t add floor area to your existing home but can make accessory spaces, like garages and basements, livable.
Does building an ADU impact property taxes in San Diego County?
Yes, but your whole property won’t be reassessed in value—your ADU will be assessed on its own, so your property taxes won’t increase by a lot.
You can expect to pay about 1-1.5% of your ADU build cost in property tax. For example, if you spent $400,000 to construct your ADU, you might pay an additional $4,000 - $6,000 in property tax per year.
Want to learn more about ADU regulations in your area?
Book a free consultation and estimate with a Cottage ADU Expert to find out what’s possible on your property!