Ever thought about turning your backyard into something more? Maybe a home office, a rental for extra income, or a private space for a family member? Accessory Dwelling Units (ADUs) make that possible, and in California, homeowners have more flexibility than ever to build them.
What is an ADU?
Accessory Dwelling Units (ADUs) are self-contained living spaces built on the same lot as a primary home. They can be detached, like a small backyard cottage, or converted from existing space, such as a garage or basement. To qualify, an ADU must have its own kitchen, bathroom, and living area and can be up to 1,200 square feet if the lot size and zoning allow it (City of San Diego).
For a smaller option, there are Junior ADUs (JADUs). These units are up to 500 square feet and must be within the existing home or attached garage. A JADU requires a separate entrance and an efficiency kitchen, but it can share a bathroom with the main home (City of San Diego).
So, how many can you build? In San Diego, single-family homeowners can add one ADU and one JADU. Multi-family properties can have up to two detached ADUs and convert 25% of non-livable spaces, like storage rooms or basements, into ADUs (City of San Diego).
ADU size depends on the lot, but most can be at least 850 square feet for a studio or one-bedroom and up to 1,000 square feet for a two-bedroom (California HCD). Properties in coastal areas may have additional rules under the California Coastal Commission (City of San Diego).
ADUs are a great way to create flexible living space. Some homeowners build them to provide a private home for their adult children, in-laws, or a live-in nanny or caregiver. Others see them as a smart investment, renting them out for additional income. They can also serve as the perfect home office, guest house, or creative studio. However you use it, an ADU can add both function and value to your property.
Photo Retrieved from Visit California
Benefits of an ADU in Our Communities
Zoning laws limit how much you can build on a property. One big restriction? Floor Area Ratio (FAR), which dictates how large a home can be relative to lot size.
In Del Mar, for example, homes are capped at 25% of lot size—meaning if you own a 10,000 sq. ft. property, your home can’t exceed 2,500 sq. ft. But here’s where ADUs are a game changer: they don’t count toward FAR, allowing homeowners to add living space without breaking zoning rules.
What does this mean in practical terms? It means that even if you’ve maxed out the size of your home under Del Mar’s zoning rules, you can still build an ADU. And while Del Mar is a great example, other communities benefit from ADUs in similar ways—even those with more flexible zoning laws
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San Diego’s ADU Bonus Program: Growth and Changes
In 2020, San Diego introduced an ADU Bonus Program to encourage more housing development. The idea was simple: homeowners could build more ADUs than state law allowed, as long as some were designated for affordable housing (City of San Diego).
What made this program stand out? Properties near public transit had no cap on the number of ADUs they could add, though most lots were limited to 10 units or fewer due to height and space regulations (KPBS).
At first, the program created new opportunities for housing and allowed developers to build smaller, more affordable rental units. However, not everyone was excited about the rapid changes. Councilmember Henry Foster III voiced concerns, stating the ADU Bonus Program “is destroying community character, impacting for-sale opportunities, and creating unsafe conditions. We must pause this program and address all unintended consequences and negative impacts that are affecting communities citywide” (KPBS).
On March 4, 2025, after hours of public discussion, the San Diego City Council voted 6-3 to revise—not repeal—the ADU Bonus Program. Rather than eliminating it altogether, the council directed city staff to create a reform plan that adjusts the program’s reach in certain areas (Fox 5 San Diego).
The decision reflects an effort to continue increasing housing options while refining the program to ensure it aligns with community planning goals.
Final Thoughts
ADUs remain a valuable tool for homeowners looking to add space—whether for rental income, family, or a home office. While San Diego is refining its Bonus Program to prevent overuse from the development side, ADU laws still offer plenty of opportunities, especially in communities with strict zoning like Del Mar. As policies evolve, now is the time to explore your options and make the most of your property.
Bibliography
California Department of Housing and Community Development (HCD). Accessory Dwelling Unit Handbook.
City of San Diego. Accessory Dwelling Units (ADU) Regulations and Guidelines.
City of San Diego Planning Department. ADU Bonus Program Overview.
City of Del Mar. Accessory Dwelling Unit (ADU) and Junior Accessory Dwelling Unit (JADU) Regulations.
KPBS. Renters, builders defend San Diego’s ADU program as council backs off repeal effort. Published March 5, 2025.
KPBS. Gloria exploring options after surprise city council vote seeking repeal of landmark housing program. Published January 29, 2025.
Fox 5 San Diego. San Diego City Council votes to begin rolling back controversial ADU program. Published March 4, 2025.
Visit California. Del Mar Travel Guide.