How Many ADUs Can You Legally Build in San Diego?

About the figures in this article. These are general San Diego market ranges for planning purposes — they are not a quote from Fortune Design & Permits. They were carried over from earlier articles, have not been reviewed against current costs, and should be treated as indicative only. Ask us for a quote on your property.

As housing demand continues to grow across Southern California, Accessory Dwelling Units (ADUs) have become one of the most effective ways for homeowners to maximize property value and create additional living space. San Diego, in particular, has adopted some of the most ADU-friendly policies in the state, making it easier than ever to build ADU in San Diego.

However, one of the most common questions homeowners ask is: How many ADUs can you legally build on your property in San Diego? The answer depends on several factors, including your property type, zoning, and local regulations.

In this guide, we’ll break down everything you need to know about ADU limits in San Diego so you can plan your project with confidence.

Understanding ADUs and Property Types

Before determining how many ADUs you can build, it’s important to understand the two main property categories:

1. Single-Family Properties

These are traditional residential homes located on a single lot.

2. Multi-Family Properties

These include duplexes, triplexes, apartment buildings, and other properties with multiple units.

Each category has different rules for ADU development.

How Many ADUs Can You Build on a Single-Family Property?

San Diego allows multiple ADU options for single-family homes, making it one of the most flexible cities in California.

Standard Allowance

On a single-family lot, you can typically build:

1 Detached ADU
1 Junior ADU (JADU)

This means you can legally have two additional units on your property.

What Is a Junior ADU (JADU)?

A JADU is a smaller unit (up to 500 square feet) created within the existing home, often using a bedroom or part of the interior space.

Bonus ADU Opportunities

San Diego’s local programs may allow additional units under certain conditions, particularly if you convert existing space such as:

Garage conversions
Basement conversions
Other non-livable areas

These conversions can sometimes be added without counting against standard ADU limits.

How Many ADUs Can You Build on a Multi-Family Property?

Multi-family properties have even more flexibility when it comes to ADU construction.

Conversion ADUs

You can convert existing non-livable spaces into ADUs, including:

Storage rooms
Garages
Laundry rooms

San Diego allows at least one conversion ADU per existing unit, depending on available space.

Detached ADUs

In addition to conversions, you can also build detached ADUs.

San Diego allows:

Up to 8 detached ADUs, depending on the number of existing units

This means a multi-family property can potentially support a significant number of ADUs, making it a powerful investment opportunity.

San Diego’s Bonus ADU Program

San Diego has introduced a Bonus ADU Program, which allows homeowners and developers to build more units than standard zoning would normally allow.

How It Works

If you agree to designate some ADUs as affordable housing, the city may allow you to build additional units beyond the typical limits.

Example

A property with one home could potentially build multiple ADUs if affordability requirements are met
Multi-family properties can significantly increase unit count through this program

This program has made San Diego one of the most ADU-friendly cities in California.

Key Requirements to Build ADU in San Diego

While the number of ADUs allowed is important, there are also requirements that must be met before construction can begin.

1. Zoning and Lot Eligibility

Most residentially zoned properties in San Diego are eligible for ADU construction. However, zoning determines:

Maximum unit count
Placement of structures
Height and size limitations

2. Setback Requirements

Setbacks determine how close your ADU can be to property lines.

Rear and side setbacks: Minimum 4 feet
Front setbacks: Based on existing zoning

3. Size Limits

ADU size depends on the type of unit:

Detached ADUs: a city must allow at least 850 sq. ft. (1,000 sq. ft. with 2+ bedrooms) — many set a higher ceiling of their own. See the current state minimums.
JADUs: Up to 500 sq. ft.
Attached ADUs: Based on main home size

4. Parking Regulations

San Diego has relaxed parking requirements significantly.

Parking is not required if:

The property is near public transit
The ADU is a conversion
The unit is located in certain urban zones

5. Utility Requirements

ADUs may require connections to:

Water
Sewer
Electrical systems

In some cases, utilities can be shared with the main residence.

Cost Considerations for Multiple ADUs

Building more than one ADU increases overall investment, but it also increases potential returns.

Typical Cost to Build ADU in San Diego

Garage conversion: $100,000 – $180,000
Attached ADU: $150,000 – $300,000
Detached ADU: $250,000 – $450,000+

Additional Costs

Design and permits: $10,000 – $30,000
Utility upgrades: $5,000 – $15,000
Site preparation: varies

Building multiple units can reduce cost per unit due to shared infrastructure and economies of scale.

Benefits of Building Multiple ADUs

San Diego’s flexible policies make it possible to maximize property potential like never before.

1. Increased Rental Income

Multiple ADUs can generate consistent monthly income.

2. Higher Property Value

More units significantly increase overall property worth.

3. Flexible Living Options

ADUs can be used for:

Family members
Guests
Home offices

4. Long-Term Investment Growth

San Diego’s strong housing market makes ADUs a valuable long-term asset.

Common Challenges Homeowners Face

Even with favorable laws, building multiple ADUs can present challenges:

Understanding zoning limits
Navigating permit approvals
Designing efficient layouts
Managing construction costs
Coordinating utilities and infrastructure

Working with experienced professionals helps overcome these challenges.

Why Work with Fortune Design & Permits

If you’re planning to build ADU in San Diego, having the right team is essential. At Fortune Design and Permits, we specialize in helping homeowners maximize their property’s potential while staying compliant with local regulations.

We provide:

Property feasibility analysis
Custom ADU design solutions
Permit processing and approvals
Full construction support

Our team understands San Diego’s ADU laws and helps you determine exactly how many units you can build on your property.

Final Thoughts

San Diego offers some of the most flexible ADU regulations in California, allowing homeowners to build multiple units under the right conditions. Whether you own a single-family home or a multi-family property, there are significant opportunities to expand your living space and increase your investment.

However, the exact number of ADUs you can build depends on zoning, property type, and local programs like the Bonus ADU initiative. Careful planning and expert guidance are key to maximizing these opportunities.

If you’re ready to explore your options, working with experienced professionals can help you move forward with confidence and avoid costly mistakes.