How El Cajon Handles Accessory Structures: A Practical Guide
El Cajon maintains 149 local ordinances across all categories, and 6 of those deal specifically with accessory structures. Here is a breakdown of what the city actually requires, what is prohibited, and where El Cajon falls on the strict-to-permissive spectrum compared to other cities.
Garage Conversions
Converting an El Cajon garage into living space is treated as an accessory dwelling unit conversion under Municipal Code § 17.140.180(E)(1): the converted structure must meet building and fire safety codes, keep independent exterior access from the primary home, and carry sufficient side and rear setbacks for fire safety. Section 17.140.170(F)(7) separately bars any converted garage entryway from facing the street.
Key details: Permit: Building permit required for any conversion. Access: Independent exterior entry from primary home. Design limit: No entryway facing the street. Size cap: 1,200 sq ft habitable, never larger than house. Parking: Lost garage space not required to be replaced.
Converting a garage without the required building permit is a code violation enforceable under the general penalty clause at El Cajon Municipal Code § 1.24.010, or through the city's administrative citation program for municipal code violations. Under § 17.140.180(I), an unauthorized or unpermitted garage conversion is not automatically ordered removed; it may instead be issued a permit to legalize the unit consistent with Government Code § 66332, provided it can be brought into compliance with the standards above, including the street-facing entryway ban.
ADU Owner Occupancy
El Cajon does not impose an owner-occupancy requirement on standard accessory dwelling units, but § 17.140.180(F)(1) requires the property owner to live in either the primary home or the junior accessory dwelling unit whenever the two share common sanitation facilities, unless the owner is a government agency, land trust, or housing organization.
Key details: Applies to: Junior ADUs with shared sanitation only. Standard ADUs: No owner-occupancy requirement. Exempt owners: Government agency, land trust, housing organization. Recording: Notice of restriction required before permit finalizes. Penalty: Non-compliance is cause for JADU removal.
Failing to honor the owner-occupancy requirement for a JADU is expressly cause to have the JADU removed under § 17.140.180(F)(1), "in accordance with appropriate procedures." A building permit for a JADU will not be finalized without proof that the recorded notice of restriction, which discloses the owner-occupancy and non-severability conditions, is on file per § 17.140.180(F)(2). Renting the unit for stays under the 30-day minimum term also violates § 17.140.180(F)(4).
ADU Impact Fees
El Cajon waives development impact fees entirely for any accessory or junior accessory dwelling unit under 750 square feet under § 17.140.180(G)(2); units larger than 750 square feet are charged impact fees only proportionately, based on the ADU's square footage relative to the primary dwelling.
Key details: Under 750 sq ft: No development impact fees at all. Over 750 sq ft: Fee charged proportionate to unit size. Governing fee chapter: El Cajon Municipal Code Chapter 17.25. Max standard ADU size: 1,200 square feet habitable. Max JADU size: 500 square feet.
There is no separate penalty tied to the fee waiver itself; the consequence of miscalculating or refusing to pay an applicable impact fee on an ADU over 750 square feet is that the building permit cannot be finalized until fees due under Chapter 17.25 are paid. Applicants who believe a fee was assessed contrary to the proportional formula in § 17.140.180(G)(2) can raise it through the permit review and hearings process set out in Chapter 17.25.
El Cajon is more permissive than most cities when it comes to adu impact fees. That said, there are still limits.
ADU Rules
El Cajon allows one accessory dwelling unit and one junior ADU on every eligible single-family lot as a matter of right under Municipal Code § 17.140.180, capped at 1,200 square feet of habitable space and never larger than the primary home including its garage. A building permit is required, but review is ministerial.
Key details: Governing section: El Cajon Municipal Code § 17.140.180. Max ADU size: 1,200 sq. ft. habitable space. Max JADU size: 500 sq. ft.. Single-family lot allowance: 1 ADU plus 1 JADU. Review process: Ministerial building permit, no hearing.
Constructing an ADU or JADU without the required building permit, or exceeding the 1,200-square-foot attached/detached cap or 500-square-foot junior ADU cap, is a Municipal Code violation enforceable under § 1.24.010 as a misdemeanor, up to a $1,000 fine and six months in county jail, or as an infraction starting at $100 for a first offense. The city can also red-tag an unpermitted unit and require it be brought into compliance or removed before occupancy is allowed.
Tiny Homes
El Cajon allows a movable tiny home only as an accessory dwelling unit behind the main house, capped at 150 to 430 square feet, and only after the owner obtains an Administrative Zoning Permit under Municipal Code Section 17.140.230.
Key details: Floor area range: 150 to 430 square feet. Placement: Rear of primary dwelling only. Permit required: Administrative Zoning Permit. Classification: Permitted only as an ADU. Utilities: Must connect to water, sewer, electric.
An MTH sited without the required Administrative Zoning Permit, placed outside the rear-of-lot ADU location standard, or exceeding the 430-square-foot cap does not qualify as a lawful accessory dwelling unit under Section 17.140.230 and is treated as an unpermitted structure subject to the city's standard zoning code enforcement process. The community development director may grant limited deviations from the general requirements, but only on a finding that safety is not compromised and that the residential character of the neighborhood is preserved; deviations are not available for the underlying permit requirement itself.
This is not one of those rules that cities tend to ignore. El Cajon actively enforces its tiny homes requirements.
Shed & Carport Rules
El Cajon exempts one-story detached tool and storage sheds up to 120 square feet from a building permit, but only on property with a single-family (R-3) home, set at least six feet from any other building. The exemption never waives the zoning code's setback and lot coverage rules.
Key details: Max exempt shed size: 120 sq ft (11.2 m2). Occupancy eligible: R-3 (single-family) only. Min. distance from other buildings: 6 feet. Setback/coverage limits: Zoning code still applies. Satellite dish exemption: 3 ft diameter, low-voltage only.
Building a shed over 120 square feet, or placing an exempt shed closer than six feet to another building or in violation of zoning setbacks or lot coverage limits, is a code violation even though no permit is required for the base structure; the building official can require correction, removal, or after-the-fact permitting under Section 105.2.4. Unpermitted work beyond the exemption's scope is enforceable the same as any unpermitted building work.
The Bottom Line
El Cajon's accessory structures rules are a mixed bag. Some areas are strict, others are relaxed, and the details matter. The best approach is to check the specific rule that applies to your situation rather than assuming El Cajon is broadly strict or permissive.
These rules come from El Cajon's publicly available municipal code. For complete penalty schedules, exemption details, and answers to common questions, see the individual ordinance pages throughout this guide.