A casita, derived from the Spanish word for "little home," is one of the most popular types of Accessory Dwelling Units (ADUs) in San Diego. While casitas are the most common ADU style in the region, this guide will explore policies applicable to all ADU types.
With rising housing costs and the increasing demand for flexible living solutions, ADUs have become a practical choice for homeowners looking to generate passive income or expand their living spaces. To ensure ADUs are functional, safe, and compliant with zoning regulations, San Diego County has implemented specific policies governing their construction and use.
Below is a brief summary of some of the most important Accessory Dwelling Unit Policies in San Diego based on official county guidelines.
What Is an ADU?
An Accessory Dwelling Unit (ADU) is a secondary residential dwelling unit that:
Measures 1,200 square feet or less.
Provides complete independent living facilities, including:
Living and sleeping areas.
A full kitchen.
A bathroom with sanitation facilities.
Is located on a lot that has an existing or proposed primary dwelling unit.
Types of ADUs in San Diego
ADUs can take various forms, including:
Attached Units: Built as part of the main residence.
Detached Units: Free-standing structures separate from the primary home.
Interior Conversions: Repurposing existing space within a structure (e.g., garages, basements, attics).
Development Regulations for ADUs
Size Restrictions
ADUs must be 1,200 square feet or less.
They must comply with development regulations like structure height, lot coverage, and floor area ratio set by the zoning laws.
Multiple-Dwelling Unit Zones
In zones where multiple dwelling units are allowed, the ADU policies vary depending on the type of space utilized for the construction:
Existing Habitable Area: Up to 25% of the total number of existing dwelling units in a structure can be converted into ADUs. If this percentage results in less than one ADU, at least one ADU is still permitted.
Non-Habitable Area Conversions: ADUs can be created from areas such as storage rooms, boiler rooms, passageways, attics, basements, and garages, with no cap on the number of ADUs allowed.
New Construction: Up to two attached or detached ADUs are permitted on a property with an existing or proposed multiple-dwelling unit structure.
Single-Dwelling Unit Zones
For properties in single-dwelling unit zones:
One ADU and one Junior ADU (JADU) are typically allowed per lot.
Multiple-Dwelling Unit Zones with Existing Single-Dwelling Unit Buildings
If a single-dwelling unit is located in a zone that permits multiple units, ADUs can be constructed without requiring additional primary dwelling units.
San Diego Housing Rent and Income Limits for ADUs
Very Low Income (50% AMI)
Studio: $45,550 annual income, $1,139 gross rent
1-BR: $52,050 annual income, $1,301 gross rent
2-BR: $58,550 annual income, $1,464 gross rent
3-BR: $65,050 annual income, $1,626 gross rent
4-BR: $70,300 annual income, $1,758 gross rent
Low Income (60% AMI)
Studio: $54,660 annual income, $1,367 gross rent
1-BR: $62,460 annual income, $1,562 gross rent
2-BR: $70,260 annual income, $1,757 gross rent
3-BR: $78,060 annual income, $1,952 gross rent
4-BR: $84,360 annual income, $2,109 gross rent
Moderate Income (110% AMI)
Studio: $82,300 annual income, $2,058 gross rent
1-BR: $94,100 annual income, $2,353 gross rent
2-BR: $105,850 annual income, $2,646 gross rent
3-BR: $117,600 annual income, $2,940 gross rent
4-BR: $127,000 annual income, $3,175 gross rent
What is AMI?
Area Median Income (AMI) is a metric used to determine the income limits for various housing programs, including those related to ADUs. AMI levels help set eligibility requirements for affordable housing options. The income categories above are based on the percentage of AMI and provide guidelines for maximum allowable gross rents for different family sizes and unit types.
Benefits of Building an ADU in San Diego
Expanded Living Space
ADUs provide additional space for family members, aging relatives, or guests.
Rental Income
Property owners can rent out ADUs to generate additional income.
Affordable Housing
ADUs can serve as a more affordable housing option for renters compared to larger homes or apartments.
Flexibility
Detached or attached ADUs can function as home offices, studios, or other multipurpose spaces.
Steps to Build an ADU
Check Zoning Regulations:Verify the zoning laws for your property to ensure ADUs are allowed.
Design and Permitting:Create a design that meets San Diego County’s size and amenity requirements. Submit the plans to the county for approval.
Construction:Build the ADU following the approved plans and ensure compliance with building codes.
Inspection and Final Approval:Schedule inspections during and after construction to receive final approval for occupancy.
Why ADUs Are a Game-Changer in San Diego
San Diego's ADU policies are designed to encourage the creation of more housing options while maintaining community standards. ADUs provide a viable solution for homeowners to contribute to the housing supply, support multigenerational living, and generate extra income, all while enhancing property value.
For more information, visit the San Diego County Planning & Development Services website or consult local zoning officials to get started on your ADU project.
Accessory Dwelling Unit (ADU) Policies in San Diego Conclusion
Accessory Dwelling Units (ADUs) offer a great opportunity to enhance your property’s potential in San Diego. By familiarizing yourself with the county’s regulations and following the correct development procedures, homeowners can create practical, compliant, and valuable additions to their properties. Whether you need extra space for family, a home office, or rental income, ADUs provide a versatile and forward-thinking solution. For more detailed information about ADU policies in San Diego, visit the official page on the San Diego County website.
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