Why Build an ADU in San Diego County?

What is an Accessory Dwelling Unit?

You may want to consider taking advantage of the change in State law which made it easier to add a second house, called an Accessory Dwelling Unit (ADU), to your residential zoned property.

An ADU is an additional dwelling unit that could provide affordable housing options for family members, friends, students, the elderly, in-home health care providers, the disabled, and others.

Granny flat, in-law suite, accessory dwelling unit (ADU), backyard cottage, tiny home – accessory dwelling units go by many names, but are always a self-contained home smaller than the main house and legally part of the same property. ADU’s can take many forms and vary in size, but always contain everything someone needs to live, including a kitchen, bathroom and place to sleep. ADU’s typically range from 400 to 1200 sf.

Where is an ADU allowed?

San Diego County ADU Regulations

An ADU can be located on residentially zoned property that has an existing single-family residence. In an effort to combat rising housing costs California passed major legislation allowing any house zoned for single-family to build a second rentable unit, known as an accessory dwelling unit. This has opened up massive opportunities for California homeowners allowing them maximize their property values. If you’re interested in building an accessory dwelling unit, you’ve come to the right place! Explore all the ADU regulations for San Diego County.

Is a Building Permit Required for an ADU?

Yes, you will be required to obtain a Building Permit to ensure that the new house meets all the zoning, building, health & safety codes.

What Size ADU is Allowed? How Big?

An ADU is intended to be secondary in size to the single-family residence. An ADU attached to a primary dwelling may be up to 50% of the size of the single-family residence, up to a maximum of 1,200 square feet. An ADU detached from the single-family residence may be up to 1,200 square feet, regardless of the size of the residence.

Examples for allowable ADU sizes are provided below:

Square Footage of Existing single-family residence (SFD)	Maximum Allowed Square Footage for Detached ADU	Maximum Allowed Square Footage for Attached ADU (up to 50% of SFD)
1,450 sq. ft.	1,200 sq. ft.	725 sq. ft.
1,800 sq. ft.	1,200 sq. ft.	900 sq. ft.
2,000 sq. ft.	1,200 sq. ft.	1000 sq. ft.
3,000 sq. ft.	1,200 sq. ft.	1,200 sq. ft.
4,500 sq. ft.	1,200 sq. ft.	1,200 sq. ft.

Why Build an Accessory Dwelling Unit?

People build ADU’s for lots of reasons, but the most common are rental income and/or to house relatives. Having a second unit is a simple and old idea to convert unused space. Second units are a relatively affordable type of construction, because they do not require purchasing land or major new infrastructure. Here are some of the reasons to build an accessory dwelling unit.

Rental Income: Many homeowners build accessory dwelling units to help pay the mortgage, because they offer a steady source of income.

California passed Senate Bill 1069 in an effort to increase the supply of housing to the state. For this reason, any accessory dwelling unit may be used for a long-term rental.

What would you do with an additional $20,000-40,000 a year?
Average Rent per Month:
San Francisco: $3,800
San Diego: $2,000
Los Angeles: $2,200
Portland: $1,900
Austin: $1,700

Rental Estimate Income-Above data based on local average property data and value

Appreciation Estimate = (Base Value: $800,000) / (Home’s Living Space: 1,350 sqft) * (ADU’s Living Space: 500 sqft)
Rental Estimate = (Rent Per Sqft: $4.79) * (ADU’s Living Space: 500 sqft)

Housing for Relatives: Accessory dwelling units allow homeowners with adult children, aging relatives or relatives with special needs to live together, but also maintain privacy

Downsizing: Some homeowners build an ADU for themselves, often in retirement, while they rent the primary dwelling.

Flexible Space: A homeowner’s needs may change over time and ADU’s allow for flexibility and for the property to adapt to new needs, such as a growing family, live-in nanny or aging in place parents.

Sound Investment: To maximize your return on investment those who build an ADU should plan to own their property for an extended period. The value passive rental income brings, especially in a city like San Diego, which boasts soaring rental prices is undeniable.

Community Benefits: ADU’s can help address the housing challenges in San Diego County by adding homes that are generally more affordable, which helps provide workforce housing and preserves diversity and community character. Many homeowners are motivated to build a second unit to rent to a school teacher, firefighter or other community member who might otherwise have to commute a long distance to find a home they can afford.

Building an accessory dwelling unit in San Diego, especially if you intend to keep the property for a few years, represents an enormously beneficial opportunity to maximize your existing property.