ADU rules in Corona

Detached ADUs are allowed on any lot zoned for single-family, multifamily or residential/commercial mixed use that has an existing or proposed primary home (CMC 17.85.030(C)); twelve zone chapters (A, A-14.4, R-1A, R-20.0, R-12.0, R-1-9.6, R-1-8.4, R-1-7.2, R-1-14.4, R-2, R-3 and R-3-C, sections 17.06.025 through 17.26.025) and the Affordable Housing overlay (17.31.040(A)(8)) list the ADU as a use allowed with a building permit under Chapter 17.85. On a single-family lot the chapter allows one detached ADU paired with either a JADU or an attached or interior ADU, two units in all (17.85.030(K)(1)); Ord. 3410 (adopted March 5, 2025) added the SB 1211 multifamily counts of up to eight detached ADUs on a lot with existing apartments, never more than the existing unit count, and two beside a proposed multifamily building (17.85.030(K)(2)(c), (K)(3)). New detached units need only 4-foot side and rear setbacks (17.85.040(F)(2)) and must be architecturally compatible with the house (17.85.040(I)). Gov. Code 66323(a), as HCD's March 2026 handbook reads it, requires a single-family lot to take a converted ADU, a JADU and a new detached ADU of up to 800 sq ft together, one more unit than Corona's two-unit cap, and the state text controls where they conflict (Gov. Code 66325).

Attached ADUs built along a shared wall of the house, and ADUs created within the existing or proposed space of the house, an attached garage, a storage area or an accessory structure, are allowed (17.85.040(A)), and a conversion may add up to 150 sq ft for ingress and egress (17.85.030(J), whose codified text says '150 feet'). The single-family pairings in 17.85.030(K)(1) are a detached ADU plus either a JADU or an attached or interior ADU, a JADU plus an interior ADU, or two JADUs. A JADU of up to 500 sq ft must sit within the walls of an existing or proposed house, with its own exterior entrance and an efficiency kitchen (17.85.050(D)(2), (E)-(G)). On multifamily lots, non-livable space such as storage rooms, boiler rooms, attics, basements or garages may be converted into at least one ADU or JADU and into units numbering up to 25 percent of the existing apartments (17.85.030(K)(2)(a)-(b)), matching Gov. Code 66323(a)(3).

17.85.040(D) caps a detached ADU at 1,200 sq ft of total floor area and an attached ADU at 50 percent of the primary unit, and counts the ADU toward the zone's lot coverage (for example 45 percent with single-story and 35 percent with two-story buildings in R-1-7.2, § 17.18.120); none of these limits applies to an ADU created inside existing space. Under 17.85.040(E) no standard may prohibit an ADU of 16 feet in height and 800 sq ft (the text says 'at least'), which keeps an 800 sq ft unit buildable despite the percentage and coverage limits, and a JADU is capped at 500 sq ft (17.85.050(D)(2)). Height follows the zone (17.85.040(F)): two stories or 30 feet in R-1-7.2, 25 feet for a single story (§ 17.18.090), above the state floors of 16 feet detached, 18 feet near major transit and 25 feet attached (Gov. Code 66321(b)(4)). Since January 1, 2026 (SB 543) state law measures the 800, 850 and 1,000 sq ft floors in interior livable space, while the 2025 local text speaks of total floor area; the state measure governs where the two differ. A detached new-construction ADU of up to 800 sq ft with 4-foot side and rear setbacks qualifies under Gov. Code 66323(a)(2) and cannot be held to lot coverage or any other local standard that section does not list (66323(b)).

Chapter 17.85 sets no owner-occupancy rule for ADUs: it requires only that the applicant be the owner of the property (17.85.030(D)), an ownership test at application with no residency duty afterward, and Gov. Code 66315 bars owner-occupancy conditions on ADUs. For JADUs the local text still requires the owner to live in the house or the JADU in every case, backed by a deed restriction recorded before the building permit (17.85.050(B), (D)(3)), with exceptions only for government agencies, land trusts and housing organizations. Since January 1, 2026, Gov. Code 66333(b) (AB 1154) requires JADU owner occupancy only when the JADU shares sanitation facilities with the house, and the state JADU article supersedes conflicting local text (66339.5), so a JADU with its own bathroom carries no owner-occupancy requirement despite 17.85.050(B). The city's ADU guide sheets (Rev. 10/2024 and the April 2026 Spanish version) still tell every JADU owner to live on the property.

An attached or detached ADU must provide one space per unit or per bedroom, whichever is less, which may sit on an existing driveway in the front setback if the driveway is at least 20 feet deep; spaces must be paved or decomposed granite, and front-yard landscaping may not be removed for them (17.85.040(B)(2)-(4)). No space is required for an ADU within the existing house or an existing accessory structure, within one-half mile walking distance of public transit (defined in 17.85.020(F) to include any fixed-route, set-fare bus stop or train station), in a historic district on the city's Register, where on-street permits are required but not offered to the occupant, or within one block of a car-share vehicle (17.85.040(B)(1), (C)), and JADUs need none (17.85.050(I)). Garages, carports and covered or uncovered spaces converted or demolished for an ADU need not be replaced (17.85.040(B)(2); Ord. 3410 added uncovered spaces for SB 1211). State law adds exemptions the local text omits: an ADU applied for together with a new home or multifamily building on a parcel that meets another exemption (Gov. Code 66322(a)(6)), and any unit built under Gov. Code 66323, such as a new detached ADU of up to 800 sq ft with 4-foot setbacks, which HCD's handbook says cannot be subjected to parking (66323(b)). The off-street parking table in 17.76.030, whose ADU rows predate Ord. 3410 (the section's history line ends with Ord. 3353 of 2022), still reads '1 uncovered space per bedroom' for attached or detached ADUs and requires replacing a house's parking converted to an ADU; both entries are superseded by 17.85.040(B)(2) as restated in 2025 and by Gov. Code 66314(d)(10)-(11).

ADUs and JADUs are 'reviewed ministerially through the plan check process for a building permit' filed with the Building Division, and the city acts within 60 days of a complete application, or later if the applicant asks; when an ADU is filed with a new house, action on the ADU waits until the house's building permit issues (17.85.060). Each residential zone lists the ADU as a use that 'may be permitted subject to approval of a building permit as provided for in Chapter 17.85' (for example § 17.18.025), so no planning entitlement or hearing is involved. Gov. Code 66317 (as amended by SB 543) adds a written completeness determination within 15 business days, deemed approval after 60 days and a written appeal to the council or planning commission; the 2025 local text does not restate those steps, but they apply directly. The Building Division's ADU flow chart quotes 10 business days for a first plan review and 5 for each recheck. Work that alters a historic resource on the Corona Register still needs Chapter 17.63 plan review by the Planning Director or, for a major alteration, the Historic Preservation Board (17.63.120(D)).

An ADU 'may be rented' but may not be sold separately from the primary unit, and rentals shorter than 30 days are barred for both the ADU and the main house (17.85.030(E)); JADUs carry the same rules (17.85.050(C)). Citywide, Chapter 5.55 (Urgency Ord. 3380 and Ord. 3381) has since October 18, 2023 made it unlawful to rent, advertise or occupy any short-term residential rental, meaning any dwelling unit or part of one rented for 30 consecutive calendar days or less, and bars hosting platforms from booking them; the permits of pre-ban rentals ran one year and could not be renewed (Urgency Ord. 3382; 5.55.030(D) and uncodified Ord. 3383), so the last legacy rentals ended by October 2024. Together these rules mean an ADU or JADU can be rented only for terms longer than 30 days, which is also the state minimum for Gov. Code 66323 units and JADUs (66323(e), 66333(g)); the municipal code has no long-term rental licensing program. Separate conveyance is limited to the qualified-nonprofit path of Gov. Code 66341, since the city has not adopted a Gov. Code 66342 ADU-condominium ordinance.