The ADU Bonus Program as a Developer Density Tool

San Diego’s ADU Bonus Program is a high-leverage infill strategy that can significantly increase unit yield—especially on multifamily-zoned sites—while staying within a predictable regulatory framework.

The program’s core premise is simple: increase residential unit count by pairing market-rate ADUs with deed-restricted affordable ADUs, while still designing within the site’s base-zone development envelope.

What developers should know up front:

Unit yield can be very high and, in some multifamily scenarios, effectively uncapped—but it is always constrained by base-zone FAR, height limits, setbacks, fire/access requirements, and site design efficiency.
The program is best suited to multifamily and higher-density residential parcels, where it can unlock substantial additional units without relying on rezones.
Recent rule changes have reduced the program’s usefulness for many single-family-zoned lots, so the most scalable opportunities are generally in multifamily zones.
A strong alternative density pathway for sites outside Complete Communities Housing Solutions (CCHS) areas—especially multifamily-zoned parcels where maximizing yield is the priority.

Key Advantage: Unlimited Density in Multifamily Zones

Multifamily-Zoned Sites (RM Zones)

Multifamily zones remain largely unaffected by recent program changes. In these zones, the ADU Bonus Program continues to allow unlimited ADUs, subject to base zoning controls.

Key rules for RM-zoned properties:

No unit cap on ADUs
Base FAR and height limits apply
Affordability requirements apply
Fire access rules may limit yield in HFSZ areas

Two primary paths exist:

RM within SDA / TPA → Unlimited ADUs (base envelope controls apply)
RM outside SDA → SB 1211 pathway (up to number of existing units, capped at 8)

This makes the ADU Bonus Program a viable alternative to density bonus law on constrained or irregular sites.

Important Distinction: Not a Single-Family Strategy

Recent updates to the ADU Bonus Program significantly limit density on single-family zoned lots, making them far less attractive for development-scale projects.

Single-Family Zones (RS)

Many RS zones are now ineligible for the Bonus Program
Remaining RS zones are subject to strict unit caps
FAR is artificially capped using an 8,000 SF calculation method
Bonus density is no longer scalable

As a result, this program is no longer intended for speculative single-family upzoning and is best deployed on multifamily-designated parcels.

Envelope Controls: Density Without FAR Relief

Unlike Complete Communities, the ADU Bonus Program does not provide FAR increases. Developers must work within:

Base zone FAR
Base zone height limits
Fire setbacks (if applicable)
Access and egress constraints

This creates a tight but predictable envelope, favoring:

Smaller unit sizes
Efficient circulation
Repetitive unit stacking
Type V wood-frame construction

In practice, this often results in higher unit counts than zoning alone would permit, even without FAR relief.

Affordability Requirements (Developer-Friendly)

The ADU Bonus Program requires affordability, but at levels that remain very close to market rents.

Current affordability standards:

Units must be rented at ≤110% Area Median Income (AMI)
15-year deed restriction for low or moderate income units
No long-term (55-year) covenant as required under other programs

At 110% AMI, rents often track closely with prevailing market conditions, making this one of the least restrictive affordability frameworks available.

Fees, Waivers & the New Community Enhancement Fee

Development Impact Fees (DIFs)

First two ADUs → DIFs waived regardless of size
ADUs ≤750 SF → No DIFs under state law
Additional ADUs >750 SF → Fees assessed on a sliding scale
No double-charging for affordable units

New: Community Enhancement Fee

Recent program updates introduce a Community Enhancement Fee for certain ADUs under 750 SF. The fee schedule has not yet been finalized, but it represents a new cost consideration for high-unit-count projects.

Despite this change, the ADU Bonus Program still offers significant fee advantages compared to traditional multifamily development.

Parking & Transit Rules

Within SDA / TPA → No parking required
Inside SDA / Outside TPA → 1 space per ADU
Site-specific reductions may apply depending on access, street width, and emergency services

This strongly incentivizes transit-adjacent multifamily sites, where parking can be fully eliminated.

Fire & Site Constraints (Critical for Feasibility)

Fire regulations can significantly affect yield and must be evaluated early:

High Fire Severity Zones (HFSZ) impose stricter access and setback requirements
Lots without two points of ingress/egress may be ineligible
Outside HFSZ, zero-lot-line ADUs up to 16’ remain allowed

Multifamily sites outside HFSZ offer the cleanest path to unlimited ADUs.

Strategic Positioning for Developers

The ADU Bonus Program works best when:

Zoning already supports multifamily use
Sites are constrained but transit-adjacent
Developers seek maximum yield without discretionary approvals
Long-term affordability covenants are undesirable

It is not a replacement for Complete Communities, but rather a parallel density tool that excels on:

Smaller RM parcels
Irregular lots
Infill sites where rezoning is impractical

How ArchiDev Studio Uses This Program

ArchiDev Studio evaluates ADU Bonus Program feasibility through:

Envelope optimization studies
Yield vs. fee tradeoff modeling
Fire and access constraint analysis
Affordability strategy alignment

Our approach is developer-first, ensuring the program is used only where it meaningfully improves project economics.

Next Steps

Not every site qualifies—but when it does, the ADU Bonus Program can unlock density that zoning alone cannot. Contact us for a site-specific feasibility analysis.

Book a Consultation

This page is provided for general informational purposes only and is intended as a high-level overview of the City of San Diego’s ADU Bonus Program as it applies to multifamily and higher-density residential development. Program requirements, fee structures, eligibility criteria, and interpretations are subject to change and may vary based on zoning, site conditions, overlay zones, fire regulations, and agency discretion. This content does not constitute legal, financial, or entitlement advice. Project feasibility, unit yield, and affordability obligations must be evaluated on a site-specific basis in coordination with the appropriate public agencies and professional consultants.