ADU rules in Temecula

Detached ADUs are a permitted ("P") use in all nine residential districts of Table 17.06.030 (HR, RR, VL, L-1, L-2, LM, M, H and HR-SM), and every planned development overlay that mentions them permits them subject to Chapter 17.23. Under the "building permit only" track (17.23.030(D), Gov. Code 66323) a single-family lot may add one detached new-construction ADU of up to 800 sq ft with 4 ft side and rear setbacks; a lot with a proposed multifamily building may add up to two detached ADUs, and a lot with an existing one up to eight but no more than the number of existing units. Under the local track (17.23.040 to 17.23.050, Gov. Code 66314) one detached ADU of up to 1,200 sq ft is allowed on a residentially zoned lot with a proposed or existing house, with 4 ft side and rear setbacks, 6 ft of separation from the house (waived where it would block an 800 sq ft unit), and a design taken from the city's free Permit Ready ADU plans or matching the house's materials and colors.

Attached ADUs (an addition that shares a wall with the house, 17.23.020) are local-track units under 17.23.050, capped at 50 percent of the existing house with the 850/1,000 sq ft floor and at 25 ft or the house's height limit, whichever is less. Conversions of space inside a proposed or existing single-family home or an accessory structure, with up to 150 sq ft of expansion for ingress and egress, use the building-permit-only track (17.23.030(D)(1)), as does one JADU of 150 to 500 sq ft inside the home, attached garages included (17.23.030(E)(1)-(2)). On a lot with an existing multifamily building, at least one ADU and up to 25 percent of the existing unit count may be created in non-livable space such as storage rooms, attics, basements or garages (17.23.030(D)(3)).

Section 17.23.050(B)(1) limits a local-track attached ADU to 50 percent of the gross floor area of an existing house (1,200 sq ft when built with a new house) and a detached ADU to 1,200 sq ft of total floor area, the same wording as Gov. Code 66314(d)(4)-(5), and adds that the limits never prohibit "an eight hundred and fifty square foot ADU or a one thousand square foot ADU that provides more than one bedroom"; the minimum is an efficiency unit. Building-permit-only units follow Gov. Code 66323: a detached new-construction unit of no more than 800 sq ft, conversions with no cap beyond a 150 sq ft ingress and egress expansion, and JADUs of 150 to 500 sq ft (17.23.030(D)(1)-(2), (E)(1)). Heights: detached 16 ft, 18 ft within one-half mile walking distance of a major transit stop or high-quality transit corridor (20 ft with a roof pitch matching the house), 18 ft on a lot with a multistory multifamily building, and attached 25 ft or the house's height limit, whichever is less, so detached units are in practice one story. Lot coverage, the front setback and the 6 ft separation give way where they would block an 800 sq ft ADU with 4 ft side and rear setbacks, and a unit may sit in the front setback only if the rear or side yard is entirely infeasible.

Chapter 17.23 imposes no owner-occupancy requirement on any ADU, consistent with Gov. Code 66315. For JADUs the code still says "The JADU or primary residence shall be occupied by the owner of record" (17.23.030(E)(7)) and writes that into the recorded declaration (17.23.030(C)(3)), but Gov. Code 66333(b), as amended by AB 1154 effective 1-1-2026, allows owner occupancy only where the JADU shares sanitation facilities with the house, and 17.23.030(E) itself says state standards govern once state law changes. In practice there is no owner occupancy for ADUs, and for a JADU only when it shares the bathroom (government agencies, land trusts and housing organizations are exempt). The city's PL-73 Planning ADU application (Rev. 01/29/26) still tells applicants the owner must occupy the house or the ADU, a rule the code does not contain.

The citywide parking table requires "1 parking space per newly constructed detached ADU except as otherwise provided in Chapter 17.23," which may be tandem on the driveway (17.24.040), and 17.23.050(E)(1) exempts any ADU within one-half mile walking distance of public transit (a bus stop qualifies under the Gov. Code 66313(m) definition the chapter adopts), in a historic district, that is part of the house or an accessory structure, in a permit-parking area where no permit is offered to the occupant, or within one block of a car share space. Building-permit-only units fall outside 17.23.050 and carry no parking requirement, and "No additional parking is required for a JADU" (17.23.030(E)(6)). Parking lost when a garage, carport or uncovered space is converted or demolished need not be replaced (17.23.050(E)(2)). The local list omits the Gov. Code 66322(a)(6) exemption for an ADU applied for together with a new house or multifamily building, which applies anyway.

Both tracks are ministerial. ADUs and JADUs that meet Gov. Code 66323 need no ADU permit and go straight to Building and Safety (17.23.030(A)); other ADUs get a ministerial ADU permit from the director of community development, with no public hearing, approved or denied within 60 days of a complete application (17.23.040(E)-(F)), followed by a building permit. Table 17.03.010 places ADUs under Administrative Approval with note 5: "State law requires the administrative consideration of secondary dwelling units. These applications cannot be promoted to the planning commission." An ADU filed with a discretionary application for a new house is decided separately without a hearing (17.23.030(J), 17.23.040(G)). Water and sewer will-serve letters, or health officer approval for a septic system, are required before the building permit (17.23.030(F), 17.23.060(C)), and Gov. Code 66317 adds the 15-business-day completeness check.

ADUs may be rented separately but not sold separately, except through a qualified nonprofit under Gov. Code 66341 (17.23.050(B)(3)); Temecula has not opted into Gov. Code 66342 condominium sales. Building-permit-only ADUs and JADUs "shall be rented only for terms of thirty-one days or longer" (17.23.030(B)), matching the longer-than-30-day terms Gov. Code 66323(e) and 66333(g) require; local-track ADUs "shall not be used for short-term rentals for less than thirty-one days" (17.23.050(B)(4)), although their recorded covenant says "thirty days or longer" (17.23.050(D)) and Gov. Code 66315 lets the city require no more than terms of 30 days or longer. Table 17.06.030 prohibits short-term rentals (under 30 consecutive days, 17.34.010) in every residential district; the city's short-term rental page says the ban covers whole homes and rooms, was reaffirmed on 1-14-2020 and carries fines of up to $1,000 a day. Each ADU needs a recorded declaration of these restrictions before the building permit is finaled; the code has no rental registration program.