Curbed Los Angeles
Guide to build an ADU in for San Diego
We've done a lot of research in order to calculate the options we show to you in this report. Still, we think that it's important for you to understand the regulations we base our interpretations from defining the terms to the design regulations. ADUs are detached or attached accessory structures on a residential lot that provide independent living areas. ADUs are intended as permanent housing solutions and shall not be used for rental terms of less than 31 consecutive days. ADUs can be integrated into existing single-family or multi-family properties. They can be designed in various ways, including converting a portion of an existing house, adding to the existing house, converting an existing garage, or constructing a new detached structure.
A. What is an Accessory Dwelling Unit for a property in San Diego?
An Accessory Dwelling Unit is an attached or detached residential dwelling unit that is 1,200 square feet in size or less, and provides complete independent living facilities for one or more persons including permanent provisions for living, sleeping, eating, cooking, and sanitation, and is located on a lot with a proposed or existing single dwelling unit or multiple dwelling units.
B. How many ADUs are Allowed on a lot?
1. Single-Family Zones
A Single-Family Zone is a zone that allows a maximum of one dwelling unit on a single lot.
a. Permitted within Single-Family Zones:
1 Single Primary Dwelling Unit
1 Accessory Dwelling Unit
1 Junior Accessory Dwelling Unit
b. Single-Family Zone Exception for Existing Multi-Dwelling Unit Buildings:
Within Single-Family Zones, where a legally permitted, previously conforming multi-dwelling unit structure exists, ADUs may be constructed under the Multi-Family Zone provisions outlined below in C.2 Multi-Family Zones.
c. Other Allowances:
In addition to the Dwelling Units, Guest Quarters and Non-Habitable Accessory Structures are also allowable.
2. Multi-Family Zones
A Multi-Family Zone is a zone that allows more than one dwelling unit on a single lot.
a. Conversions or Interior Alterations of Existing Structures
Existing Habitable Area: The maximum number of ADUs permitted within the habitable areas of an existing multiple dwelling unit structure is 25% of the total number of existing dwelling units. 1 ADU is permitted where the percentage calculation yields less than 1 ADU.
Existing Non-habitable Area: The number of ADUs permitted within the non-habitable areas of an existing multiple dwelling unit structure is unlimited. Examples include storage rooms, boiler rooms, passageways, attics, basements, and garages.
b. Addition of Floor Area to Existing Structures
New additional floor area to an existing multiple dwelling unit structure may not be used for the creation of ADUs.
c. Construction of New Detached Structures
A maximum of 2 detached ADUs are permitted on premises with an existing multiple dwelling unit structure. The 2 ADUs may be within one structure or two separate structures.
d. Multi-Family Zones with an existing Single Dwelling Unit Building
Within Multi-Family Zones, where a legally permitted single-dwelling unit structure exists, the premises may construct ADUs by the Multi-Family Zone provisions outlined above in C.2.a through
The premises may construct the ADU(s) without a requirement to construct any other additional standard dwelling units.
C. How large can you build an ADU in San Diego?
1. The minimum gross floor area for an attached or detached ADU is 150 square feet.
2. The maximum gross floor area for an attached or detached ADU is 1,200 square feet.
3. The gross floor area of an ADU is included in the total gross floor area of the premises.
4. An ADU may exceed the total gross floor area of a premises, however, the ADU shall be limited to a maximum of 800 square feet of gross floor area.
5. Minimum room dimension requirements contained within the California Building Standards Code are applicable.
CityStructure ADU report helps you see and understand the size and location of a possible ADU for your lot.
Deciding which ADU option works best for you is not easy. Order your ADU Analysis for each option to make sure you evaluated all your options.
D. ADU Setback Regulations
1. Conversions or Interior Alterations of Existing Structures
Where an existing structure is converted to an ADU, the ADU may continue to observe the setbacks of the existing structure.
2. Demolition and Reconstruction of Existing Structures
Where an existing structure is demolished and reconstructed as an ADU, the ADU may continue to observe the setbacks of the original structure. The reconstruction must beat the same location and to the same dimensions as the original structure.
3. Addition of Floor Area to Existing Structures Where an addition to an existing structure is proposed for an ADU, the ADU must observe the Front and Street-Side Setbacks of the Zone. The ADU may encroach into the Side and Rear Setbacks of the Zone, including up to the Property Line.
4. Construction of New Detached Structures Where a new structure is proposed as an ADU, the ADU must observe the Front and Street-Side Setbacks of the Zone. The ADU may encroach into the Side and Rear Setbacks of the Zone, including up to the Property Line.
5. ADUs must comply with all requirements in the California Building Standards Code, including requirements for fire separation distance, opening protection, allowable height, and allowable area.
E. ADU Parking Regulations
1. No parking spaces are required for ADUs.
2. The conversion or demolition of a garage, carport, or covered parking structure does not require the replacement of parking spaces.
3. Where off-street parking spaces are provided, parking spaces may be within setback areas, and in any configuration including tandem configurations and mechanical lifts.
4. Where off-street parking spaces are provided, parking spaces must be entirely within the property line of premises and must conform to the dimension standards of SDMC Chapter 14, Article 2, Division 5.
F. ADU Other Regulations
1. The property owner is not required to live on-site.
2. An ADU may not be leased for a term of less than 31 consecutive days. An ADU may not be used for Transient Lodging.
G. ADU Fire Sprinkler Systems.
Reference Technical Bulletin RESD 3-4 for fire sprinkler requirements in ADUs.
H. ADU Solar Photovoltaic Systems
1. Newly constructed ADUs are subject to the California Energy Code requirement to provide solar panels if the unit(s) is a newly constructed, non-manufactured, detached ADU. Per the California Energy Commission (CEC), the panels can be installed on the ADU or on the primary dwelling unit.
2. ADUs that are constructed within existing space, or as an addition to existing homes, including detached additions where an existing detached building is converted from non-residential to residential space, are not subject to the California Energy Code requirement to provide solar panels.
I. ADU Bonus Program
1. For-Lease Affordable Program
a. Inside of Transit Priority Areas, for every qualifying on-site deed-restricted ADU(Table 141-03A), one additional non-deed-restricted bonus ADU is allowed.
b. Inside Transit Priority Areas, where a Project proposes qualifying on-site deed-restricted ADUs (Table 141-03A), the maximum number of bonus ADUs is unlimited.
c. Outside of Transit Priority Areas, where a Project proposes qualifying on-site deed-restricted ADUs (Table 141-03A), the maximum number of bonus ADUs is one.
2. For-Sale Affordable Program
a. For qualifying 501.c.3 Developers, reference SDMC 141.0302.b.1.B for program details.