What Are the ADU Requirements in San Diego? (2025 Update)

Thinking about building an ADU on your property? You’re not alone. Homeowners across the city are adding Accessory Dwelling Units for rental income, multigenerational living, or simply to increase property value (especially with updated San Diego ADU requirements making the process more accessible).

But before you start designing or budgeting, there’s one key question to answer:

What do the San Diego ADU requirements actually allow on your lot?

This article breaks it down clearly, covering zoning, lot size, setbacks, parking, and other rules that impact what you can build and where.

In most cases, yes.

San Diego allows ADUs on nearly all residential properties. But whether you can build one depends on a few key conditions related to your lot, zoning, and the existing structures on the property.

To qualify for an ADU, your property must meet these baseline requirements:

• Zoned for residential use (single-family or multifamily)

• Contains an existing primary dwelling

• Meets access and safety standards (for fire, egress, etc.)

• Has enough buildable space for the size and type of ADU you want to construct

🔍 Important: Just because ADUs are legal doesn’t mean every lot qualifies for every type of ADU. That’s why zoning and design reviews still matter and why it helps to check before you design or apply.

Under California state law (SB 9, AB 68), San Diego no longer enforces a minimum lot size for ADUs. That means even small lots can qualify, as long as they meet other criteria.

What does matter is how your lot is zoned:

• Single-family residential zones (e.g., RS-1-7): You’re allowed one ADU and one Junior ADU

• Multifamily zones (e.g., RM-1-1, RM-3-7): You may be eligible to build two detached ADUs plus convert non-livable areas (like storage rooms or laundry rooms) inside the primary structure

If your lot is in a Coastal Overlay Zone, near a steep slope, or subject to other zoning overlays, you may need additional review. These zones don’t prevent ADUs, but they can affect height, placement, and extend processing time due to stricter zoning and setback requirements.

🧭 Not sure what your lot is zoned for? You can use San Diego’s zoning lookup tool or speak with a contractor who understands local ADU regulations in San Diego.

In San Diego, the number and size of ADUs you’re allowed to build depends on two things:

1. What your property is zoned for, and

2. How much space on your lot you actually have to work with.

Here’s how the rules break down:

Single-Family Zoned Lots

• You can build 1 ADU (either attached or detached)

• You can also build 1 Junior ADU (JADU) inside the existing home

• The detached ADU can be up to 1,200 sq ft

• The JADU is limited to 500 sq ft and must be built within the existing home

Multifamily Zoned Lots

• You can build up to 2 detached ADUs

• You can also convert non-livable spaces (like storage rooms, boiler rooms, garages, etc.) inside the existing structure into more units — no set limit as long as space and code allow

Size Limits

• Detached ADUs: Up to 1,200 sq ft (regardless of lot size)

• Attached ADUs: Up to 50% of the main house’s size (sometimes larger depending on San Diego ADU size limits)

• JADUs: Maximum 500 sq ft by law

⚠️ These are the maximums, your actual buildable space may be smaller depending on setback requirements or lot coverage rules.

You might’ve heard that San Diego allows more than two ADUs on a single property. That’s partly true, but it only applies under the city’s Bonus ADU Program, which is designed for larger projects with deed-restricted affordable housing.

Unless you’re planning to build multiple ADUs for rent and are open to income limits and city oversight, this program probably doesn’t apply to you.

But if you’re curious, here’s the official info:

👉 San Diego Bonus ADU Program-SDHC

Where you place your ADU on the lot isn’t up to you alone. There are setback rules that determine how close the structure can be to your property lines and they change depending on the type of ADU and location on the lot.

Here’s a breakdown of what to know:

Detached ADUs

• Side and rear setbacks: Minimum 4 feet

• Front setbacks: Varies by zoning, but ADUs are typically not allowed in front yards unless special conditions are met

• Distance from main home: While there’s no strict minimum in the zoning code, San Diego generally applies a 5-10 foot separation between the ADU and the main house as a fire safety standard. However, if your design includes alternative fire-rated construction (like fire-resistant siding and no window openings between structures), the ADU can legally sit as close as 3 inches from the main home.

10′ separation from existing main house for privacy and functionality

Attached ADUs

• Treated as an extension of the primary home

• Must follow the same setback rules as the main structure

• In zones where the main house has a nonconforming setback, the attached ADU can often continue that line

Garage Conversions & JADUs

• Setback rules usually don’t apply if you’re converting an existing structure

• However, if you’re expanding the structure (like popping the garage out in the back), those new parts must meet the 4-foot rear/side minimum

⚠️ Other ADU Placement Restrictions to Know

• ADUs generally aren’t allowed in front of the main home unless your lot meets specific conditions or variances are granted

• Sloped lots or hillside zones may have additional rules (like geotechnical review or retaining wall requirements)

• Fire access lanes or utility easements can also impact where your ADU can legally go

In many cities, adding an ADU means having to add a parking space. But San Diego takes a more relaxed approach in most cases.

When You Don’t Need to Add Parking

You do not need to provide parking for your ADU if:

• Your property is within half a mile of a public transit stop

• The ADU is part of the existing home or accessory structure (like a garage conversion or JADU)

• The ADU is located within a historic district

• Street parking permits are not required in your area

These exemptions apply to most homes in central San Diego neighborhoods.

When You Might Need Extra Parking

If none of the above apply (for example, if your lot is in a remote hillside area with no transit nearby) the city may require one off-street parking space per ADU.

This space can be:

• Tandem in a driveway

• On an existing paved surface

• Covered or uncovered

However, if you’re converting an existing garage to an ADU, you’re not required to replace the parking you removed. That’s one of the most homeowner-friendly aspects of San Diego’s ADU rules.

Building an ADU in San Diego is more accessible than ever, but San Diego ADU requirements like zoning, setbacks, unit limits, and parking still matter, and they vary depending on your property and plans.

Before hiring a designer or submitting plans, it’s worth getting clear on what your property actually allows. That way, you avoid wasting time or money while chasing something the city won’t approve (dive deeper on the entire ADU construction timeline before making any big decisions).

One simple way to start is by contacting your local building department. You can usually email or schedule a quick appointment to ask what’s required, how the process works, and what applies to your specific lot.

You can also give us a call if you’re looking for a reliable one stop shop San Diego ADU builders. We’ll help you figure out what makes sense for your property or at least point you in the right direction.

No strings attached.