ADU rules in La Mesa

Detached ADUs are allowed with an existing or proposed home on any lot zoned for single-family or multifamily use (R1E, R1R, R1S, R1, R1A, R2, R3 and RB) and in the Mixed Use Overlay, through a ministerial building permit. The 2023 code text counts one detached ADU per single-family lot and two on a multifamily lot, but the city's June 2026 Development Matrix applies the state counts instead: on a single-family lot one ADU under the local standards (attached or detached, up to 1,200 sq ft), one conversion unit and one new detached unit of up to 800 sq ft, plus a JADU; on a lot with an existing multifamily building up to eight detached units, never more than the existing units. Detached units need 4 ft side and rear setbacks, and on designated historic sites they must sit behind the main house.

Attached ADUs (additions) and conversions of space inside the home or an existing accessory structure are allowed in every residential zone and the Mixed Use Overlay; a conversion may add up to 150 sq ft beyond the existing structure for ingress and egress (§ 24.05.020.D.8.e.i). A JADU of up to 500 sq ft may be created inside a single-family home alongside an ADU (§ 24.05.020.D.9). In existing multifamily buildings, non-livable space such as storage rooms, attics, basements and garages can become ADUs, at least one and up to 25 percent of the existing units. The city matrix lists a conversion ADU, an attached ADU and a JADU as separate allowances on single-family lots.

The code caps any attached or detached ADU at 1,200 sq ft of floor area (§ 24.05.020.D.8.a.ii) and guarantees an 800 sq ft unit with 4 ft side and rear setbacks regardless of lot coverage, front setback, open space or lot size (D.8.a.vi); lots of 10,000 sq ft or less with an existing home get 5 percent extra lot coverage for an ADU. The city's June 2026 Development Matrix, which staff use to apply current state law, also holds an attached ADU to 50 percent of the existing primary dwelling (the Gov. Code 66314(d)(4) limit the code text omits) and lists the state-exempt detached unit at up to 800 sq ft (66323(a)(2)). JADUs are capped at 500 sq ft inside the home, and the matrix sets a 150 sq ft minimum unit size. Height is 20 ft measured to the plate line in the R1 zones and R2 and 30 ft in R3 and RB.

Neither the code nor the city matrix requires the owner to live on a property with an ADU, and Gov. Code 66315 bars that condition. The 2023 JADU text still says the owner must occupy the main home or the JADU and must record a covenant saying so (§ 24.05.020.D.9.e and D.9.k(iv)), but since 1-1-2026 Gov. Code 66333(b) limits owner occupancy to a JADU that shares sanitation facilities with the house, and the city's 2026 matrix applies that narrower rule. A JADU covenant is still recorded before the building permit issues.

No new or additional parking is required for any ADU (§ 24.05.020.D.8.f.i; the § 24.04.050.A(8) parking table reads 'No parking spaces required'), and none for a JADU beyond what the house already needed (D.9.f(v); 24.04.050.A(9)). Parking removed when a garage, carport or covered space is demolished or converted for an ADU need not be replaced (D.8.f.iii), and the 2026 matrix extends that to any replacement parking, matching Gov. Code 66314(d)(11). The city's 2025 Housing Element progress report ties the citywide waiver to the closeness of most residential land to transit. Parking an owner chooses to provide must meet the Chapter 24.04 design standards.

ADU and JADU applications that meet the standards are 'considered ministerially without discretionary review or a hearing' and decided within 60 days (§ 24.05.020.D.8.h.iii and D.9.l), now on Gov. Code 66317's 15-business-day completeness check and 60-day clock. Applications run through the MaintStar portal as building permits, the city has offered free pre-approved ADU plans since 1-1-2025, and its 2025 Housing Element report lists all 81 ADU permits that year as ministerial. Scenic Preservation and Hillside overlay standards still apply but without Planning Commission review (D.8.d). Exception: work on a designated historic landmark or in a designated historic district needs a Certificate of Appropriateness decided by the Historic Preservation Commission at a public meeting (§ 25.03.040), which two ADUs went through in 2025.

An ADU may be rented but not sold or conveyed separately from the main home, except to a qualified low- or moderate-income buyer through a qualified nonprofit under a recorded tenancy-in-common agreement (§ 24.05.020.D.8.i.ii-iii, the Gov. Code 66341 path); the city has no ADU-condominium (66342) ordinance. The code requires rental terms longer than 30 days only for the state-exempt units built under D.8.e and for JADUs (D.9.d), matching Gov. Code 66323(e) and 66333(g), while the city's 2026 matrix prints 'rental terms must exceed 30 days' for every ADU type. La Mesa has no short-term rental permit or registration program: a 7-14-2026 council memo says the city has no regulatory framework for short-term vacation rentals and does not collect TOT from them, and the council voted 5-0 that night to have staff return within six months with a proposed policy.