ADU Rules Guide · San Diego
San Diego ADU Rules Explained: What You Can Build in 2026
State law has overridden many local restrictions. Here's what's actually allowed on your San Diego property — and what your city can and can't say no to.
Types of ADUs Allowed in San Diego
California law now allows multiple ADU types on most residential lots. San Diego follows state law, which overrides many older local restrictions that previously limited ADU construction:
| ADU Type | Max Size | Location | Separate Entrance Required |
|---|---|---|---|
| Detached ADU | 1,200 sqft (state max) | Separate structure on lot | Yes |
| Attached ADU | 50% of primary home (max 1,200 sqft) | Addition to main house | Yes |
| Garage Conversion ADU | Existing garage footprint | Convert existing garage | Yes |
| Junior ADU (JADU) | 500 sqft | Within primary dwelling | Yes (can share entrance) |
| Internal Conversion | Existing space only | Basement, bonus room, etc. | Yes |
Under AB 2221 (effective January 2023), most single-family lots in San Diego can have one ADU plus one JADU, for a total of two additional dwelling units beyond the primary home.
Setback Requirements for San Diego ADUs
This is where California state law made its biggest impact on local ADU rules. Prior to 2020, San Diego required 5-foot setbacks on sides and rear for new ADU construction. State law now mandates:
- Side and rear setbacks: 4 feet minimum for new detached ADUs (state law, supersedes local rules)
- Front setback: Must comply with local zoning — typically 5–20 feet depending on neighborhood
- Height: Detached ADUs can be up to 16 feet tall (or 18 feet within ½ mile of transit); two-story ADUs are allowed in many zones
- Lot coverage: San Diego limits total lot coverage including the ADU — typically 50–60% depending on zone
- Garage conversions: No setback requirement if the existing garage already meets setbacks
The 4-Foot Rule Is State Law
If a San Diego neighbor or city official tells you that you need more than 4 feet of setback for a new ADU, that may be outdated information. California Government Code Section 65852.2 sets the 4-foot minimum as a floor — cities cannot require more. Always verify with a current permit application, not verbal guidance.
ADU Permits and Fees in San Diego
San Diego's permit process for ADUs has improved significantly since 2020. Here's what to expect:
- Permit applications: Submit through San Diego's Development Services Department (DSD) via their ePDC (Electronic Plan Development Center) portal
- Review timeline: ADU applications are supposed to be approved or denied within 60 days. In practice, plan for 60–90 days for a detached ADU
- Impact fees: State law limits impact fees for ADUs under 750 sqft — San Diego cannot charge them for these smaller units
- ADUs 750 sqft and larger: Full impact fees apply, which can add $15,000–$40,000 to total project cost
- School fees: San Diego Unified charges school impact fees — roughly $4.79/sqft of new habitable space (2026 rate)
- No owner-occupancy requirement: The law that required the property owner to live on-site expired in 2025 and was not renewed under current California law
| ADU Size | Impact Fees | School Fees (approx) | Total Approx Fee Load |
|---|---|---|---|
| Under 750 sqft | Waived | $900–$2,400 | $900–$2,400 |
| 750–1,000 sqft | Full fees apply | $2,400–$3,200 | $18,000–$45,000 |
| 1,000–1,200 sqft | Full fees apply | $3,200–$3,840 | $22,000–$55,000 |
What San Diego Cannot Restrict
State law has stripped cities of several ADU restrictions that were common before 2020. San Diego cannot:
- Require owner-occupancy (expired, not renewed as of 2025)
- Require more than one additional parking space for an ADU within ½ mile of public transit
- Prohibit ADUs based on lot size alone (if the lot meets minimum zoning requirements for a home, an ADU is generally allowed)
- Require more than 4 feet of side/rear setback for new detached ADU construction
- Require architectural compatibility with the primary home (though good design is always advisable)
- Charge impact fees for ADUs under 750 sqft
HOAs and ADUs
HOAs in California cannot prohibit ADU construction, but they can impose reasonable design standards (color, materials, roofline). If you're in an HOA, submit your ADU plans to the HOA for design review before submitting to the city — the city review takes precedence, but managing both processes in parallel saves time.
Frequently Asked Questions
Answers to what San Diego homeowners ask most.
Yes, in most cases. California state law allows detached ADUs on nearly every single-family lot in San Diego with only 4-foot side and rear setbacks. The key requirements are meeting the setbacks, staying under 1,200 sqft, and complying with lot coverage limits.
Detached ADUs in San Diego typically cost $200,000–$350,000+ depending on size and finishes. Garage conversions run $80,000–$150,000. Junior ADUs (within the existing home) run $40,000–$90,000. Impact fees can add $15,000–$50,000 for ADUs over 750 sqft.
No. California's owner-occupancy requirement expired in 2025 and was not renewed. You can build an ADU on a property you own as a rental without living there yourself.
State law requires cities to approve or deny ADU applications within 60 days. In practice, San Diego DSD takes 60–90 days for a detached ADU with a new foundation. Garage conversions and JADUs typically move faster.
Yes, in many zones. State law allows ADUs up to 16 feet tall (18 feet within ½ mile of transit). Two-story ADUs are permitted, though local height and setback rules still apply. Some hillside zones and coastal overlay zones have additional restrictions.
A Junior ADU (JADU) is a smaller unit — max 500 sqft — created within the walls of the primary dwelling. It can share an entrance with the main home but must have an independent cooking area. JADUs have a simpler permit process and lower fees than a full ADU.
Yes. ADUs can be rented as long-term rentals (12+ months) without restriction. Short-term rentals (Airbnb/VRBO) are subject to San Diego's short-term rental ordinance, which requires a license and limits STR permits in residential zones.
Have a question not covered here? Call (831) 261-7329 or send us a message. We answer the phone.
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