Guide · ADU Rules
Can I Build a Granny Flat on My Property in San Diego?
California state law has made it easier than ever to add a granny flat to a San Diego property. Here's exactly how to know if you qualify — and what to watch out for.
The Short Answer: Probably Yes
If you own a single-family home in San Diego and your property is zoned residential, you almost certainly qualify to build at least one ADU (granny flat) under California state law. The state has preempted most local restrictions that used to make ADUs difficult or impossible.
The main eligibility requirements are: the lot must be zoned for single-family or multi-family residential use, the primary structure must already exist on the lot, and the ADU must meet minimum setback requirements (4 feet from rear and side property lines for detached ADUs).
Key Rule: California Overrides Local Zoning
State law (AB 68, SB 13, AB 881) prevents cities and counties from using zoning rules to block ADU construction. San Diego cannot require a minimum lot size, owner-occupancy, or additional parking as conditions for ADU approval.
What Lot Requirements Apply in San Diego?
Here are the key rules that determine whether you can build a granny flat in San Diego:
| Requirement | State Law Rule | San Diego Application |
|---|---|---|
| Zoning | Must be residential | RS, RM, and other residential zones all qualify |
| Existing structure | Primary home must exist | Applies to all ADU types |
| Rear/side setback (detached ADU) | 4 ft minimum | San Diego cannot require more |
| Front setback | Matches existing primary dwelling setback | Varies by lot |
| Maximum ADU size | Up to 1,200 sq ft detached | Or 50% of primary home's sq ft |
| Height limit | 16 ft for detached ADU (18 ft near transit) | Taller permitted by local rule in some cases |
| Parking | Not required within ½ mile of transit | Most urban San Diego lots qualify |
| Owner-occupancy | Not required | You do not need to live on the property |
What Situations Make It More Complex?
While most San Diego properties qualify for a granny flat, a few situations add complexity:
- Coastal Overlay Zone: Properties in La Jolla, Del Mar, Encinitas, and Solana Beach require a Coastal Development Permit in addition to standard ADU approvals. This adds 4–8 weeks to the permit timeline.
- HOA restrictions: Some HOAs still attempt to restrict ADU construction. State law generally preempts HOA rules, but enforcement requires legal review if your HOA objects.
- Historic districts: Properties in designated historic zones may face additional design review requirements, though the state has limited cities' ability to block ADUs on historic grounds.
- Lot access: Properties with limited rear or side access may require creative site planning for a detached ADU. Utility connections can also be a constraint on some lots.
- Flood zones: Properties in FEMA flood zones have additional requirements for foundation height and waterproofing.
None of these situations necessarily prevents you from building a granny flat — they just require additional planning. During our free consultation, we assess your specific parcel for all of these factors.
How Long Does the Permit Process Take?
The City of San Diego must approve or deny an ADU permit application within 60 days under state law. In practice, plan for 60–90 days for standard permits, and 4–6 months for coastal zone properties requiring a CDP.
We handle the entire permit process: architectural drawings, structural engineering, plan submittal, plan check responses, and inspector coordination. Homeowners are not required to appear at the permit office.
Frequently Asked Questions
Answers to what San Diego homeowners ask most.
State law eliminated minimum lot size requirements for ADUs. San Diego cannot require a minimum lot area for ADU approval. Even small lots (under 5,000 sq ft) can qualify for a Junior ADU or garage conversion, and may qualify for a small detached ADU depending on setback requirements.
California state law (AB 670) generally prohibits HOAs and CC&Rs from preventing ADU construction, except for ADUs visible from streets in limited circumstances. If your HOA objects, we can help you understand your rights and navigate the process.
A Junior ADU is up to 500 sq ft, carved from the existing square footage of your primary home, with its own entrance (can share with the main home) and a kitchenette. A standard ADU is a new or separately permitted unit — detached, attached, or a garage conversion — with a full kitchen and private entrance. You can build one ADU and one JADU on the same lot under state law.
Have a question not covered here? Call (831) 261-7329 or send us a message. We answer the phone.
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