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What you can build

El Cajon ADU Regulations & Zoning

KEY RULES AT GLANCE
Size and Separation

Maximum size: 1,200 square feet

Side/rear setbacks: 4 feet

Two story: Yes

Building separation: Minimum 6 feet

Additional Requirements

Soils Report: No

Building Verification Survey: No

Coastal permit (in some areas): No

Stormwater Mitigation: No

Number of ADUs Allowed

  • On single-family residential lots in El Cajon, property owners are allowed to build one ADU (either attached or detached) and one Junior ADU (JADU)

  • Currently, El Cajon allows up to two detached ADUs on multifamily lots that already have an existing multifamily building. This means that to qualify for two ADUs, the property must have at least a duplex—a single-family home does not qualify.

    • Multifamily property owners will be allowed to build as many ADUs as there are existing units, with a maximum of eight detached ADUs.

    • This change follows California state law, which will override local regulations that are not updated to comply.

    Conversion ADUs

    • Existing non-livable spaces within a multifamily building, such as storage rooms and garage spaces, may be converted into ADUs.

    • The maximum number of conversion ADUs allowed in a multifamily building is 25% of the total existing units (rounded down).

    However, at least one conversion ADU is always permitted.

ADU Size & Building Constraints

  • The maximum size for an attached or detached ADU in El Cajon is 1,200 square feet, but it cannot be larger than the primary dwelling unit. Additionally, ADUs up to 800 square feet are exempt from lot coverage requirements, allowing them to be built even if the property has already reached its maximum lot coverage.

  • An ADU in El Cajon can be built up to the maximum height allowed by the underlying zoning when it is located within the primary dwelling unit's setback requirements. This means a two-story ADU is permitted as long as it complies with zoning regulations.

    For ADUs located outside of the primary dwelling unit setbacks, height limits vary based on setbacks:

    • 20 feet with 5-foot setbacks

    • 16 feet with 4-foot setbacks

    • 12 feet with 3-foot setbacks

    If the ADU is within ½ mile walking distance of a major transit stop or a high-quality transit corridor, the height limit is 18 feet, with up to 2 additional feet allowed if the roof pitch matches that of the primary dwelling.

    For lots that already have a single-family or multifamily dwelling that is two or more stories, the ADU height is limited to 18 feet.

  • Yes, covered patios, porches, and similar attached covered areas intended for use by the ADU occupant are allowed. However, these areas—excluding garages or carports—must not exceed 10% of the ADU’s total floor area.

  • An ADU must be built using similar materials, colors, and architectural style as the primary dwelling unit.

    For ADUs larger than 800 square feet, El Cajon requires wall plan articulation for any wall longer than 30 feet. This means the wall must include a “jog” that is at least 18 inches deep and extends for a minimum of 4 feet to create visual interest and avoid long, flat surfaces.

Setbacks

  • Setback requirements for ADUs in El Cajon vary based on the height of the unit:

    • 5-foot setbacks for ADUs up to 20 feet in height

    • 4-foot setbacks for ADUs up to 16 feet in height

    • 3-foot setbacks for ADUs up to 12 feet in height

    Alternatively, if the ADU complies with the underlying zoning setbacks, it may follow the maximum height permitted by the zoning regulations.

  • The minimum required separation between an ADU and any existing structures on the property is 6 feet.

Additional Requirements 

  • No, El Cajon allows digital submission of ADU applications.

  • Yes, El Cajon is currently the only known municipality that requires a sewer lateral video.This inspection is typically conducted during the feasibility phase of the project, and in some cases, a higher-definition video may be necessary.

    According to the City of El Cajon Public Works Wastewater Administration Department (as of June 2022):

    Property owners are responsible for maintaining the entire private sewer lateral, including both the upper and lower sections within the right-of-way or easement, from the building to the City sewer main connection. Since this lateral serves only a single property, it is not considered part of the municipal sewer system.

    If any digging or replacement work is needed within the right-of-way (ROW) or easement, a separate Encroachment Permit (EP) and appropriate traffic control measures will be required. However, if the lower lateral can be repaired using a cured-in-place liner without disrupting the ROW with active work, vehicles, or obstructions, an Encroachment Permit may not be necessary.

  • No, El Cajon does not require a soils report for ADUs.

  • No, El Cajon is not subject to Coastal Development requirements.

Parking

  • A parking space is not required for an ADU if any of the following conditions apply:

    • It is located within ½ mile walking distance of public transit, including bus stops.

    • It is within an established historic district.

    • It is converted from existing space within a primary residence or accessory structure, or is attached to an existing or proposed primary dwelling.

    Starting in January 2025, if a garage, carport, covered parking structure, or uncovered parking space is demolished or repurposed to construct an ADU, replacement parking will not be required.

  • If a parking space is required, it can be placed within the setbacks or in an existing driveway as tandem parking. Additionally, when a garage, carport, or covered parking structure is demolished or converted to build an ADU, the parking space does not need to be replaced.

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