What you can build
El Cajon ADU Regulations & Zoning
ADU regulations are complex, but when you’ve done this for 100+ projects, you know the details inside and out. We publish our insights because we want people to get accurate information… not just regurgitated bullet points. Our summary was last updated in April 2026.
Key Facts SnapShot
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
Permitting timeline
Standard Timeline: 5-6 months
Coastal Timeline: N/A
Permit Costs: $12-14/sqft
Our ADU experience in El Cajon
El Cajon just updated their municipal code to comply with the new state laws, and our summary below assumes those changes in effect. El Cajon allows for digital submissions with a clear tracking system. Turnaround times at the city are moderate.
Number of ADUs Allowed
How many ADUs can you build in El Cajon?
On single-family lots in El Cajon, state law now supports a broader mix of ADU types than many homeowners previously realized. Under California law, a single-family property may combine:
- one standard ADU under the regular local-rules pathway
- one detached ADU up to 800 square feet
- one ADU created from existing space in the primary home or an accessory structure
- one JADU created from existing space in the primary residence, up to 500 square feet
HCD’s updated 2026 ADU Handbook explains that local agencies must allow the single-family combinations described in Government Code section 66323 and, in addition, must allow at least one unit described in section 66314.
However, note that local adoption will take some time.
Read more in our guide to how many ADUs you can build on a single-family property.
How many ADUs does El Cajon allow for multifamily properties?
El Cajon allows at least 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)
Multifamily property owners are permitted to build as many ADUs as there are existing units, with a maximum of eight detached ADUs.
Additionally, a minimum of one accessory dwelling unit, or up to 25 percent of the existing multifamily units, is permitted within an existing multifamily dwelling, as a result of the conversion of non-habitable space including, but not limited to, storage rooms, boiler rooms, passageways, attics, basements, or garages.
Read more about the rules around how many ADUs you can build on a multifamily lot.
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 & height limits and building an ADU above a garage.
Can you add covered patios or other areas?
Attached covered patios, porches, and similar covered areas intended to used 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′.
Setbacks
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.
Multifamily
How many ADUs does El Cajon allow for multifamily properties?
Multifamily property owners are permitted to build as many ADUs as there are existing units, with a maximum of eight detached ADUs. This change is due to California state law and will pre-empt existing local laws that are not brought into conformance.
Additionally, a minimum of one accessory dwelling unit, or up to 25 percent of the existing multifamily units, is permitted within an existing multifamily dwelling, as a result of the conversion of non-habitable space including, but not limited to, storage rooms, boiler rooms, passageways, attics, basements, or garages.
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.
Parking
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.
Effective Jan 2025 (SB1211): When a garage, carport, covered parking structure, or uncovered parking space is demolished or converted for construction of an ADU, replacement parking will not be required.
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.
Additional El Cajon ADU Regulation Resources
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About SnapADU
Since 2020, we’ve focused exclusively on designing, permitting, and building over 100 ADUs in San Diego. Our deep experience means we catch what others might miss, and our in-house team ensures every promise is delivered.
Learn MoreHow much will an ADU rent for in El Cajon?
Below are median rental prices by zip code and bedroom count. Be sure to run comps for your specific area or check with a realtor.
RENT RATES IN EL CAJON
| Zip | City | Neighborhood | 1BR | 2BR | 3BR |
| 92020 | El Cajon | Grossmont | 1780 | 2215 | 2920 |
Source: Rentometer March 2026. Note: Because ADUs are still a relatively small portion of the rental market, many comparables come from apartments, condos, or single-family homes. Smaller ADUs are usually compared to apartments, while larger ADUs are often compared to single-family homes. New construction ADUs may be able to command slightly higher rents than older apartment units.