What you can build

El Cajon ADU Regulations & Zoning


Size and Separation

Maximum size 1,200 square feet

Side/rear setbacks 4 feet

Two story Yes

Building separation 6 feet

Additional Requirements

Soils Report No

Building Verification Survey No

Coastal permit (in some areas) No

Stormwater Mitigation No

Number of ADUs Allowed

How many ADUs can you build in El Cajon?

On El Cajon single-family residential lots, you may build one ADU (either attached or detached) and one Junior ADU (JADUs have an owner occupancy requirement and must be converted from existing space within the primary residence).

How many ADUs does El Cajon allow for multifamily properties?

El Cajon allows up to 2 detached ADUs for multifamily lots with an existing multi-family building. (Meaning: In order to build 2 ADUs, the property must already have at least a duplex on it, not just a single family dwelling)

Non‐livable space within existing multi‐family structures may be converted into an ADU. Examples of areas that can be converted include storage rooms and garage spaces. The maximum number of ADU allowed in a multi‐family structure is equal to 25% of the number of existing multi‐family units in the structure. Fractional units are rounded down. A minimum of one conversion ADU is allowed.

ADU Size & Building Constraints

What size ADU can you build in El Cajon?

The maximum size of an attached or detached ADU is not more than 1,200 sqft, but under no circumstances shall the ADU be larger than the primary dwelling unit.

Lastly, ADUs up to 800 square feet are exempt from lot coverage requirements. (Meaning: You can build an ADU of this size even if you’re maxed out on lot coverages).

What is the height requirement for an ADU in El Cajon? Can you build a 2-story ADU in El Cajon?

ADU height may be as high as the underlying zone when located within the primary dwelling unit setback requirements. So yes, you may build a two story ADU so long as it conforms to underlying zoning.

Height limitations for areas outside of the primary dwelling unit setbacks are as follows:

  • Maximum height of 20 feet with 5 foot setbacks; no more than 16 feet with 4 foot setbacks; not more than 12 feet with 3 foot setbacks.
  • When the ADU is withing 1/2 mile walking distance of a major transit stop or a high-quality transit corridor, the height is limited to 18′ with up to two additional feet permitted to accommodate a roof pitch so long as it is aligned with the roof pitch of the primary dwelling
  • When the ADU is located on a lot with an existing or proposed single or multifamily dwelling that is two or more stories, the height is limited to 18′

Read more about two story ADUs and height limits.

Can you add covered patios or other areas?

Attached covered patios, porches, and similar covered areas intended to bused by the occupant of the ADU, except for a garage or carport, shall be limited to a max of 10% of the floor area of the proposed unit

What are the requirements of the exterior of the ADU?

The proposed accessory dwelling unit shall be constructed of similar building materials, colors, and with a similar architectural style to the primary dwelling unit.

For units over 800 sqft, El Cajon has a design requirement of “wall plan articulation” for lengths of wall beyond 30′. In other words, there must be a “jog” of at least 18″ deep in the wall and continue for at least 4′.


What is the setback requirement for an ADU in El Cajon?

ADUs setbacks vary depending on the height of the unit as follows:

  • Maximum height of 20 feet with 5 foot setbacks
  • Maximum height of 16 feet with 4 foot setbacks
  • Maximum height of 12 feet with 3 foot setbacks
  • Or maximum height conforming with underlying zoning setbacks
What is the minimum distance the ADU must be from existing structures?

The minimum required distance between structures is 6′.

Additional Requirements

Does El Cajon require in-person submission of plans for an ADU?

No, El Cajon allows digital submission of applications for an ADU.

Does El Cajon require a sewer line video?

Yes, El Cajon is the only municipality we are currently aware of that requires a sewer lateral video. This video is something SnapADU handles during the Feasibility portion of the project, though sometimes a higher-definition video inspection may also be required.

Per the City of El Cajon Public Works Wastewater Administration Department as of June 2022:

“Property owners are responsible for their entire private lateral (upper and lower within the right-of-way/easement) from the building up to and including the connection with the City sewer main, since the private sewer main is the exclusive use of a single party and not a part of the municipal system.

Any dig/replace work within the ROW/easement would require a separate encroachment permit (EP) and traffic control, as needed. If a lower lateral can be repaired with a cured-in-place liner without active work, vehicles, obstructions, etc. in the ROW an EP would not (likely) be required.”

Does El Cajon require a soils report for an ADU?

No, El Cajon does not mandate soils reports for ADUs.

Does El Cajon require coastal development permits?

No areas are subject to Coastal requirements.


How many ADUs does El Cajon allow for multifamily properties?

Up to two detached ADUs on lots zoned to allow multifamily dwelling units with existing multifamily dwelling units, subject to four foot side and rear setbacks and height limit of 16′

Can you stack detached ADUs on top of each other?

Yes, you may be able to stack ADUs if total height is still in conformance with underlying zoning height limits and setbacks.

Can you attach two ADUs to each other in El Cajon?

Attaching ADUs may be allowed, though is not specified in the El Cajon code.

Can you convert existing space to an ADU?

Yes, existing non-livable space may be converted to ADUs (e.g. storage areas and garages). The minimum number of ADU conversions allowed is one, up to a maximum equal to 25% of the number of existing multifamily units. This is in addition to the allowed number of detached ADUs.


What is the parking requirement for an ADU in El Cajon?

A parking space is not required for an ADU in any of the following instances:

  • Within a one-half mile walking distance from public transit, which includes bus stops.
  • Within an established historic district.
  • Converted from the existing space of a primary residence or accessory structure, or are attached to an existing or proposed primary residence.
Where can a parking space be located?

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.