San Diego ADU Regulations & Zoning

You can build two detached ADUs on multifamily lots in San Diego, plus a potential bonus of additional units if restricted to low or moderate income housing, just as described above for single family.

On a premises located in a Single Dwelling Unit Zone with an existing multiple dwelling unit, or a premises located in a Multiple Dwelling Unit Zone with an existing or proposed dwelling unit, two ADUs that are attached to and/or detached from an existing or proposed structure are permitted.

In other words, you can build two ADUs in a multifamily zone (even if there is just one single family residence) OR in a single family zone where an existing multifamily structure (like a duplex) exists.

Additionally, existing non-livable space may be converted to ADUs (e.g. storage areas and garages). In the City of San Diego, there is no limit on the number of ADUs that can be created in this manner. These conversions are in addition to the two allowed attached and/or detached ADUs.

Again, the ADU Bonus Program in the City of San Diego may allow you to build even more units.

In the City of San Diego, the square footage of any attached ADU may be up to 1,200 sqft. Note that the City of San Diego does not tie a size limit to the size of the primary home like many other local jurisdictions do.

The height of a detached ADU can be at least 16′ and still have reduced setbacks of zero on the side and back yard. You can actually build higher than 16′ in San Diego, subject to the height maximums for the underlying zone and subject to 4′ side and rear setbacks (specifically “if the side or rear property line abuts another premise that is residentially zoned or developed with exclusively residential uses.”)

Max building height in San Diego for most residential properties is 24′ to 30′, with a few going up to 35′. (§131.0444 Angled Building Envelope Plane / Maximum Structure Height in Residential Zones).

Two-story ADUs are allowed in San Diego, per the above info on height requirements. However, for ADUs located above a garage or other accessory building, the maximum height for flat-roofed structures is 21′ and the maximum structure height for sloped-roofed structures is 30′ (§141.0307 (f) Guest Quarters or Habitable Accessory Buildings).

Also note that the City of San Diego requires all stairs to be a minimum of 5′ from the property line (or more, typically stairs follow the underlying setbacks) and also requires that two-story units that are on a property abutting another residential property must adhere to 4′ setbacks.

Read more about two story ADUs and height limits.

Yes, you can stack ADUs on top of each other in San Diego. (Per City of San Diego Planning department consult Oct 2021)

No, a junior accessory dwelling unit (JADU), must be created from existing space within the primary residence.

Note that as of December 2023 with the Housing Action Package 2.0, the City of San Diego closed the option to allow you to create a new JADU attached to the ADU.

Generally roof decks would be permitted, but must meet the height restrictions for the zone. Roof decks cannot encroach into the required setbacks. Generally railings & access staircases above 42″ are included in height calculations.

San Diego makes no mention of specific requirements for the exterior of the ADU. However, general guidance is that the exterior roofing, trim, walls, windows and the color palette of the ADU shall incorporate the same features as the primary dwelling unit.

Per San Diego Municipal Code 131.0450, detached dwellings shall maintain 6 ft min. distance between dwellings on the same premises.

Also note that fire codes will require special materials – and possibly fire rating on the existing primary dwelling – when closer than 10′ eave to eave between structures.

Yes, you may build an ADU in the front yard, so long as it conforms to setbacks for that zone. Additionally, California state law allows you to build at least an 800 sqft ADU, even if it encroaches in the front setbacks, if it will not fit elsewhere on the property.

No, San Diego does not mandate soils reports for ADUs.

Yes, accessory dwelling units developed within the coastal zone are subject to a coastal development permit (CDP). This process recently changed. On September 7, 2022, the California Coastal Commission certified (W15) the City of San Diego’s changes to their Local Coastal Program (LCP). Plans are now approved by city staff and cannot be appealed to the Planning Commission or City Council so long as they comply with existing zoning and building regulations.

There will still be noticing requirements, and this will all take more time and money. We do not know exactly what the process will look like yet in San Diego because it is so new, but it will essentially be a longer and more expensive standard ADU submission with more paperwork requirements to make sure compliance with all coastal zone rules that are not covered or preempted by the State ADU laws.

Read more about ADUs in the coastal zone.

If construction of an ADU or JADU that would bring the number of ADUs or JADUs on the premises to a total of two or more is proposed, two trees shall be provided on the premises for every 5,000 square feet of lot area, with a minimum of one tree per premises. If planting of a new tree is required to comply with this section, the tree shall be selected in accordance with the Landscape Standards of the Land Development Manual and the City’s Street Tree Selection Guide.

Once plans are submitted for pre-plan check review, typically within 3-5 days the City of San Diego will issue the invoice for a “Plan Check Fee, which covers the entire cost to review plans by the city. The city will not formally start reviewing the plans until this fee is paid.

Plan check fees will be around $1,500-$2,500. Thereafter, the city technically has 60-days to do their first review of the plans, which they are fully taking at this time. They will then provide corrections to the plans that will be addressed by the designer and resubmitted. Plan check reviews after this initial phase take about 30-days. Overall, the plan review time can take around 90-100 days.

Once your plans are deemed “approved,” the project is placed in an “issuance” queue that takes another 15-20 days for the city to process. During this time you will be provided with additional fees, such as Building Permit Fee (similar in cost to plan check fees), school impact fees (depending on your school district may vary), and various small sewer/water meter review fees. Read more about ADU permit fees.

If a parking space is required, it may be located within the setbacks and in an existing driveway as tandem parking. Parking spaces don’t need to be replaced when a garage, carport, or covered parking structure is demolished in conjunction with the construction of an ADU or converted to an ADU.