Accessory Dwelling Units

The following information provides property owners in the unincorporated areas of San Diego County with information about Accessory Dwelling Units (ADUs) and whether one can be built on their property.

An accessory dwelling unit (ADU) is a structure someone can live in without relying on another structure for basic needs like bathrooms and kitchens. It can be detached (not connected to the main house) or attached (connected to the main house). An ADU must be on the same lot as the main house.

A Junior ADU (JADU) is a type of ADU that must be completely contained within an existing or proposed house. If the JADU has direct (interior) access to the main house, it can share bathrooms with the main house. JADUs can be a maximum of 500 square feet.

New: ADU Handbook

For more detailed information ADUs, please see our ADU Handbook. It includes additional commentary about the types and sizes of ADUs, discussion of topics of consideration, and a summary of the steps to build an ADU, from start to finish.

Notice: ADU Fee Waiver Program has Ended

The County of San Diego trial impact fee waiver went into effect January 9, 2019, and ended on January 9, 2024.

If you started your qualifying project before January 9, 2024, you did not pay the plan check fee. However, if your permit was not issued by January 9, 2024, you will need to pay all fees that are typically collected at permit issuance.

ADU and JADU Eligibility

You may be able to add an ADU or JADU to your property. The exact requirements depend on your specific scenario, but at least you must meet the following:

• Your property must be in the unincorporated areas of the County of San Diego

• Your property must be considered “residential”

• Your property must already have an existing or planned main house or single-family dwelling (SFD) 

All ADUs and JADUs must follow the County’s regulations.

Accessory Dwelling Unit Building Plans Available

Type of ADUs

ADUs can be made in many shapes and styles. For example, they can be detached, attached, new construction, or conversions.  

Zoning Requirements

An ADU or JADU can be located on a residentially zoned property that has an existing single-family residence. You can check your property’s zoning with your property’s Property Summary Report. You’ll need your Accessor’s Parcel Number (APN) to run the report.

The County of San Diego (County) Planning & Development Services (PDS) has a new Director's Determination Letter, which is a public document that provides an official assessment based on facts and legal guidelines. This determination clarifies how the County's Zoning Ordinance aligns with California State law confirming that when there is a conflict between the two, State law takes precedence over any provisions of the Zoning Ordinance. This letter reaffirms the County's existing practice of ensuring local regulations comply with State law, particularly when implementing any housing-related process and standard. 

Building Permit Requirements

You will need to get a building permit to make sure your ADU meets all the zoning, building, and health and safety codes. To get your building permit, you will need to turn in essential submittal items and follow the County’s submittal steps.

Size Requirements

In general, an ADU should be smaller than the main house on the same lot.

Attached ADU

The total area of an attached ADU can be up to 50% of the total area of the SFD (but limited to 1,200 square feet max). Exceptions to the 50% limit (but not the 1,200 square feet limit) may apply if the main house has more than one bedroom. 

Detached ADU

More Information

Please email PDS.ADUQuestions@sdcounty.ca.gov or PDSZoningPermitCounter@sdcounty.ca.gov if you have additional questions about ADUs or JADUs.