ADU rules in El Cajon

Detached ADUs are a permitted use (P) in every single-family zone (RS-40 to RS-6) and multifamily zone (RM-6000 to RM-HR) under Table 17.140.210, subject to § 17.140.180, and need only a building permit. On single-family lots the local track allows one ADU plus one JADU, but § 17.140.180(B) also allows every combination in Gov. Code 66323, including an 800 sq ft detached new-construction unit beside a converted ADU and a JADU. Lots with existing multifamily buildings may add up to eight detached ADUs (never more than the number of existing units) plus conversions of at least one and up to 25 percent of the existing unit count, and proposed multifamily projects may add two detached units. New detached units must stay out of the front and street-side setbacks unless that would block an 800 sq ft unit. The one gap is the PRD (Planned Residential Development) zone, where the table marks ADUs X even though the zone permits attached and detached homes; state law overrides that, at least for the state-exempt units.

Attached ADUs (additions) and conversions of existing space, including attached garages and accessory buildings, are permitted in the same RS and RM zones with a building permit. A conversion needs building and fire code compliance, its own exterior access and side and rear setbacks sufficient for fire safety; a new attached unit must meet the zone's standards except where they would block an 800 sq ft unit with three-foot side and rear setbacks. A JADU of up to 500 sq ft may be created within the walls of the existing or proposed home (attached garages count as part of the home) with an efficiency kitchen and its own exterior entrance, and needs no parking.

Section 17.140.180(C)(2) caps attached and detached ADUs at 1,200 sq ft of habitable space and never larger than the primary dwelling counted with its attached non-habitable space such as a garage; attached covered patios and porches used by the ADU occupant count toward the cap. Under (C)(1) a state-exempt Gov. Code 66323 unit (the 800 sq ft detached unit) is allowed regardless of the home's size, lot coverage or open space, and (C)(4) caps a JADU at 500 sq ft. Detached units may use the zone height (35 ft in RS zones) when they meet the main home's setbacks; otherwise 20 ft at a 5 ft setback, 16 ft at 4 ft and 12 ft at 3 ft, with 18 ft (plus 2 ft for a matching roof pitch) within a half mile walking distance of a major transit stop or high-quality transit corridor and 18 ft on a lot whose home has two or more stories. Attached units likewise get the zone height within the main home's setbacks but only 16 ft at a 4 ft setback since Ord. 5173, below the 25 ft (or the zone height, if lower) that Gov. Code 66321(b)(4)(D) guarantees attached ADUs. The code prints no 50 percent cap for attached units.

No owner-occupancy requirement applies to ADUs, and Gov. Code 66315 bars one. For JADUs, Ord. 5173 (adopted 2-10-2026, effective 30 days later) narrowed § 17.140.180(F)(1) to the state rule: the owner must live in the main home or the JADU only when the JADU shares sanitation facilities with the home (governmental agencies, land trusts and housing organizations are exempt), matching Gov. Code 66333(b) as amended by AB 1154. A notice of restriction must be recorded before a JADU permit is finaled. The city's ADU Loan Program separately requires a borrower's home to stay owner occupied, but that is a loan condition, not a zoning rule.

Section 17.140.180(D) requires one additional paved off-street space per ADU, which may be tandem or sit in the front setback on paved parking. No space is required within one-half mile of public transit (the state definition counts bus stops), in a historic district, for a unit that is part of the existing or proposed home or an accessory structure, for a JADU, where on-street permits are required but not offered, within one block of car share, or when the ADU is permitted together with a new single-family or multifamily dwelling. Garages, carports and covered parking removed for an ADU need not be replaced. State law trims the rule in ways the code does not print: parking may not exceed one space per unit or per bedroom, whichever is less (so a studio owes none on a plain reading of 66314(d)(10)(A)), state-exempt 66323 units cannot be held to standards that section does not authorize (66323(b)), and replaced uncovered spaces are waived too (66314(d)(11)).

ADUs and JADUs are permitted uses that need only a building permit (§ 17.140.180(A)), reviewed ministerially under Gov. Code 66317 (15 business days to deem an application complete, 60 days to act, no hearing); projects are filed through the city's online Project Assistance Center (PACO). ADUs other than state-exempt units must meet the objective single-family design standards of § 17.140.170, and only a request to deviate from them needs an Administrative Zoning Permit, a Community Development Director decision that can be referred to the Planning Commission. A movable tiny home (150 to 430 sq ft, built to recreational-vehicle standards) can serve as an ADU only with an Administrative Zoning Permit under § 17.140.230. El Cajon is inland, so no coastal permit applies.

ADUs may be rented but not sold separately from the main home (Gov. Code 66314(d)(1); the code has no 66342 condominium opt-in), and § 17.140.180(F)(3) bars separate sale of a JADU. Renting any dwelling is a business needing a city license (EMC 5.04.030), taxed at $40 a year plus $20 per unit (5.08.135). State law requires rentals longer than 30 days for JADUs (66333(g)) and for ADUs built under the state-exempt pathway (66323(e)); the local JADU rule in (F)(4), 'not less than 30 days', is one day short and yields. El Cajon has no short-term rental ordinance or permit: the code mentions short-term rentals only in a sign definition, and the Finance Department's TOT page says short-term or vacation rentals owe the 10 percent transient occupancy tax (stays of 30 days or less, Chapter 3.44) and need an active business license, so no text found bars short-term use of a local-track ADU. ADUs built with the city's ADU Loan Program must be rented at affordable rents for terms of at least 30 days and never as vacation rentals.