ADU Regulations

El Cajon

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9 min read

A knowledgeable ADU builder in El Cajon is essential for a successful build.


Understanding local Accessory Dwelling Unit (ADU) regulations in El Cajon is crucial for homeowners considering an ADU project. These regulations are designed to ensure that your project aligns with legal standards and optimizes property use, thereby enhancing value and functionality. This guide provides a comprehensive overview of the ADU regulations in El Cajon to help you navigate the process with confidence.

Essential ADU Rules for El Cajon

What you can build

  • Maximum Sizes

    Maximum size is 1200 sqft.
  • Setbacks

    Minimum of 4 feet is required from rear and side-yard property lines.
  • Two-Story ADUs

    Allowed, within the specific height restrictions of the zoning area.
  • Building Separation

    Minimum of 6 feet is required.

Permitting timeline

  • Permitting Timeframe

    4-6 months.
  • Coastal

    Not required.

El Cajon ADU Regulatory Overview

El Cajon’s approach to ADU regulation emphasizes flexibility and sustainability. The city permits various types of ADUs, including detached, attached, conversion, and junior ADUs (JADUs), under specific conditions to accommodate the diverse needs of homeowners. Notable aspects include the allowance of two-story ADUs under certain height limits and the emphasis on design criteria that ensure ADUs are compatible with the main residence and neighborhood character.

El Cajon ADU Permitting Process

The ADU permitting process in El Cajon involves several steps:

  • Preparation

Gather necessary documents, including plans and site maps.

  • Submission

Submit your ADU application along with the required documentation to the El Cajon Planning Department.

  • Review

The city reviews your application, a process that can take approximately 60 days, depending on the complexity of the project.

  • Approval

Once approved, you’ll receive permits to begin construction, followed by inspections at various stages.

ADU Local Zoning in El Cajon

A single-family property in El Cajon is allowed one ADU and one JADU, offering flexibility to homeowners looking to expand their living space or housing options.

In El Cajon, properties with existing multi-family buildings, such as duplexes, can have up to two detached ADUs. Non-livable spaces within these multi-family structures, like storage rooms and garages, can also be converted into ADUs. The allowable number of conversion ADUs is capped at 25% of the existing multi-family units, rounding down fractional units, with a minimum of one conversion ADU permitted.

ADU height can match the zoning of the underlying zone when within primary dwelling unit setbacks, allowing for two-story constructions. Outside these setbacks, height limits are: a) 20 feet with 5-foot setbacks; b) 16 feet with 4-foot setbacks; and c) 12 feet with 3-foot setbacks. Near a major transit stop or high-quality transit corridor, the height is generally capped at 18 feet, with up to 20 feet permissible to align the roof pitch with the primary dwelling. For ADUs on lots with multi-story dwellings, the height limit remains at 18 feet.

Yes, El Cajon permits the construction of two-story ADUs within the overall height limits specified by the zoning area, allowing homeowners to maximize their property’s potential.

The allowance for roof decks on ADUs is not directly addressed in the regulations. Property owners interested in adding such features should consult the El Cajon Community Development Department for tailored advice, ensuring compliance with safety and design standards.

Attached ADUs are capped at 1200 square feet and may not be larger than the primary dwelling unit.

ADU Building Codes in El Cajon

In El Cajon, ADU setbacks vary with unit height as follows: a) a maximum height of 20 feet requires 5-foot setbacks; b) a height of 16 feet requires 4-foot setbacks; c) a height of 12 feet requires 3-foot setbacks; or d) the maximum height conforms to the underlying zoning setbacks.

ADUs must maintain a 6-foot separation from existing buildings.

El Cajon simplifies the ADU construction process by not requiring soils reports, thus lowering barriers for homeowners to develop ADUs.

ADUs can be assigned separate mailing addresses through coordination with the city’s engineering department and the USPS, enhancing the autonomy and functionality of the ADU as an independent unit.

El Cajon accommodates the digital submission of ADU plans via its Project Assistance Center Online (PACO), reflecting the city’s commitment to streamlined and accessible permitting processes.

While El Cajon generally allows ADUs to share utilities with the primary dwelling, specific projects, especially those with unique requirements or significant utility demands, may necessitate separate connections. Homeowners should verify specific utility arrangements based on their ADU’s specifications and city guidelines.

Finalizing Your ADU in El Cajon

El Cajon streamlines the ADU development process with clear guidelines on submission and verification. Homeowners must ensure their ADU plans meet local zoning and building codes. Parking requirements are waived under specific conditions, such as proximity to public transit, facilitating the integration of ADUs into existing residential areas. ADUs can be used for long-term rentals, contributing to the city’s housing supply, but cannot be sold separately from the primary residence. Utilities for ADUs typically connect to the main house’s services, although specific projects may require independent connections based on size or location.

Calculate Your ADU Cost in El Cajon

Using the tool below, you will be able to calculate your investment based on the type and size of the ADU you are interested in building on your property.

Attached ADU


Estimated Cost


*The costs we are calculating here are an average for time and materials. This calculator is meant to provide an estimate to educate you on the ADU building process, please note that this is not a final quote.

Detached ADU


Estimated Cost


*The costs we are calculating here are an average for time and materials. This calculator is meant to provide an estimate to educate you on the ADU building process, please note that this is not a final quote.

Garage ADU


Estimated Cost


*The costs we are calculating here are an average for time and materials. This calculator is meant to provide an estimate to educate you on the ADU building process, please note that this is not a final quote.
Start building


Navigating ADU regulations in El Cajon requires a thorough understanding of local zoning laws, building codes, and the permitting process. By adhering to these regulations, homeowners can successfully develop ADUs that enhance their property’s value and functionality. For tailored advice and the most current information, consulting with the El Cajon Planning Department or legal professionals is highly recommended. Whether for rental income, accommodating family, or other uses, ADUs represent a valuable asset for property owners in El Cajon.


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