Over the past decade, San Diego has approved thousands of accessory dwelling units (ADUs) as part of a broader housing strategy focused on affordability and infill development. What started as statewide ADU reform under California state law has expanded locally into something more aggressive: the San Diego Bonus ADU Program.
At Streamline Design & Permitting, a San Diego-based drafting and permit coordination firm, property owners often ask us whether they can realistically build four, six, or even eight units on a single lot. The answer depends on factors like zoning, location, and affordability commitments, not just lot size.
Build More Than One ADU — Here’s How It Works
The San Diego Bonus ADU Program is a local housing initiative that the San Diego City Council adopted to increase housing supply in transit-accessible neighborhoods.
Under standard California ADU state law (Government Code §65852.2), most single-family properties can build:
- 1 detached ADU
- 1 junior ADU (JADU)
Multifamily properties can convert existing non-livable space into accessory dwelling units, with a limited number of additional detached ADUs allowed.
The San Diego Bonus ADU Program goes further. It allows additional unrestricted ADUs when at least one unit is deed-restricted for affordable housing. This makes the program different from standard ADU rules. It isn’t simply about adding one backyard unit; it’s about increasing density on qualifying residential properties.
Who Can Qualify, and What You Must Provide
Not every property in San Diego qualifies for the bonus ADU program. Location and affordability commitments determine eligibility.
1. The Property Must Be in the Right Area
Most projects must be located in:
- Transit Priority Areas (within ½ mile of major transit stops)
- Sustainable Development Areas
- Zones that are not restricted by wildfire hazard regulations
The City of San Diego planning review confirms whether a property meets these geographic requirements.
2. You Must Include an Affordable ADU
To unlock bonus density, property owners must build:
- One affordable ADU
- Deed restricted for low-income households or moderate-income households
In exchange, the city allows:
- One additional unrestricted ADU
- Or multiple additional unrestricted ADUs, depending on zoning and lot characteristics
The San Diego Housing Commission provides AMI limits and housing affordability guidelines used in calculating allowable rents.
Affordable ADUs aren’t market rate. They require:
- Income verification
- Recorded deed restrictions
- Compliance with affordability timelines
Only once these requirements are met does the city allow additional unrestricted ADUs. Together, location and affordability form the foundation of the San Diego Bonus ADU Program. Without both, the density increase doesn’t apply.
How Many Units Can You Actually Build?
This is the most common question we get about the San Diego Bonus ADU Program: How many ADUs can I build on my property?
The answer depends on:
- Underlying zoning
- Transit overlay location
- Lot size and configuration
- Existing dwelling units
- Floor area ratio (FAR) limits
- Height limits
- Setbacks from property lines
- Fire access requirements
Typical Single-Family Scenario
In a Transit Priority Area, a single-family lot may allow:
- 1 detached ADU
- 1 junior ADU
- 1 affordable ADU
- 1 additional unrestricted ADU
That often results in 3-4 total accessory dwelling units, depending on constraints.
Typical Multi-Family Scenario
Multi-family lots may allow:
- Conversion ADUs inside existing space
- One affordable ADU
- Multiple bonus ADUs
Some multifamily properties have produced 6–8 total accessory dwelling units under the bonus ADU program in San Diego.
However, there’s still a specific limit tied to building envelope, infrastructure capacity, and life-safety requirements. The program increases density but doesn’t remove physical constraints.
What Rules Still Apply? (Density Isn’t Unlimited)
The San Diego Bonus ADU Program increases unit count, but it doesn’t eliminate development standards. Even bonus ADUs must comply with building regulations.
Height Limits
Detached ADUs typically follow:
- 16 feet standard
- Up to 24 feet near transit in certain zones
Height restrictions still impact how many units can physically fit on a lot.
Setbacks
State law allows:
- 4-foot side setbacks
- 4-foot rear setbacks
Front setbacks may still apply depending on zoning.
Floor Area Ratio (FAR)
Some zones impose FAR limits that cap total square footage on the property, which must also stay consistent with statewide California ADU size limit regulations for detached and attached units. Even when additional units are allowed by count, FAR may still limit the overall buildable area.
Parking Requirements
Within Transit Priority Areas, parking requirements are often waived. Outside those areas, parking standards may apply.
Fire & Emergency Access
Projects must maintain clear emergency access routes and comply with fire code standards.
The Permitting Process
The permitting process includes:
- Zoning verification
- Site plan review
- Affordable housing documentation
- Recording deed restrictions
- Plan check corrections
City staff carefully review bonus ADU applications, and the process is more complex than a standard single detached ADU submission.
Each of these stages follows the standard procedural framework required under San Diego building permit regulations for residential construction.
The Financial Trade-Off: More Units vs. Rent Restrictions
The San Diego Bonus ADU Program increases total unit count, but affordable housing requirements impact revenue.
We’ve included a simplified comparison:
Advantages of the Program
- Ability to build more units
- Increased overall housing production
- Potential long-term property value growth
- Strong infill development strategy
Challenges to Consider
- Rent caps on affordable ADUs
- Income verification requirements
- Recorded deed restrictions
- More complex approvals
Research from the Terner Center for Housing Innovation shows that ADUs have played a measurable role in expanding housing across California. San Diego’s local program amplifies this effect, but property owners must balance unit volume with affordability requirements.
The right choice depends on long-term goals, financing strategy, and property constraints, including eligibility for common San Diego ADU financing programs used for multi-unit projects. For others, maximizing total units under the bonus ADU program in San Diego produces more long-term value.
Why the City Supports This Program
Under Mayor Todd Gloria, San Diego has prioritized infill housing and increased residential density near transit.
The San Diego City Council has described the San Diego Bonus ADU Program as a housing innovation strategy. Instead of relying solely on large-scale new development, the city promotes:
- Backyard homes
- Granny flats
- Small-scale housing projects
- Additional ADUs integrated into existing neighborhoods
The goal is to distribute new housing throughout established communities while increasing housing affordability.
Is the San Diego Bonus ADU Program Right for Your Property?
The San Diego Bonus ADU Program is a great way to increase development potential, but only on qualifying properties and only with affordable housing commitments. Streamline Design & Permitting provides zoning analysis, ADU drafting, and permit coordination throughout San Diego County. Our consistent approach and hands-on experience give us the confidence to navigate any situation and handle your project with expertise. Contact us to evaluate your property and determine your true ADU capacity under the San Diego Bonus ADU Program.
