ADU rules in Lancaster

Detached ADUs are permitted by right: the residential zones matrix (17.08.050) lists 'Accessory dwelling unit and junior accessory dwelling units' as P (permitted) in every residential zone (RR-2.5, RR-1, SRR, R-15,000, R-10,000, R-7,000, MDR and HDR), the mixed-use matrix (17.10.050) does the same in MU-N, MU-C and MU-E, and existing homes in the CPD, OP, P and SP zones may add ADUs despite those zones' caps on expanding a residence. A new detached ADU on a single-family lot must meet 17.41.016.A.4: 18 feet in height (20 feet if needed to match the main roof pitch), a 25-foot front setback, 4-foot side and rear setbacks and the zone's lot-coverage cap. The code allows 'no more than one JADU and one ADU' per parcel (17.41.016.A.1.a), but Gov. Code 66323(a) requires ministerial approval of any combination of a conversion ADU, an 800 sq ft detached ADU and a JADU on a single-family lot, and state law supersedes the conflicting count (66325(a)). On multifamily lots the code still says two detached ADUs (17.41.016.B.1.a.2), while the city's 2026 ADU Application already allows up to eight, never more than the number of existing units, as Gov. Code 66323(a)(4) requires.

Attached ADUs and conversions are allowed on the same lots: an attached ADU is new construction joined to the main house (17.41.016.A.3), limited to 25 feet and two stories with a 25-foot front setback and 4-foot side and rear setbacks, and an interior ADU may be carved out of the existing or proposed house or an existing accessory structure (plus up to 150 sq ft for ingress and egress) with independent exterior access and side and rear setbacks sufficient for fire safety (A.2). A JADU of up to 500 sq ft with an efficiency kitchen may be created entirely within a single-family structure, including an attached garage (17.41.012.F). On multifamily lots, interior ADUs may be built in non-livable space such as storage rooms, attics, basements or garages, at least one and up to 25 percent of the existing or proposed units (17.41.016.B.1.a.1, B.2). A garage converted to an ADU or JADU follows Article I rather than the two-space replacement rule for ordinary garage conversions (17.08.220.A).

LMC 17.41.016 caps an attached ADU on a single-family lot (A.3.b) and a detached ADU on a multifamily lot (B.3.b) at 850 sq ft for a studio or one-bedroom unit and 1,200 sq ft for two or more bedrooms, and neither the 25-foot front setback nor the lot-coverage caps (40 percent in RR-2.5, RR-1, SRR, R-15,000 and R-10,000; 50 percent in R-7,000, MDR and HDR; 60 percent in mixed-use zones) may push those units below 850 sq ft. The matching cap for a detached ADU on a single-family lot (former A.4.b) was struck by Ord. No. 1130 (adopted May 27, 2025), although its amendment table describes item 38 as removing detached ADU size limits 'for multifamily developments', so the adopted text now limits single-family detached ADUs only by height, setbacks and lot coverage while keeping the multifamily cap, the reverse of the stated intent; HCD's March 2026 handbook confirms a local ordinance may allow ADUs above 1,200 sq ft (Gov. Code 66325(b)). The city's 2026 ADU Application nonetheless lists 850 sq ft (0-1 bedroom) and 1,200 sq ft (2+ bedrooms) for single-family detached units, and its June 2026 pre-approved plan FAQ says state law allows attached and detached ADUs up to 1,200 sq ft with attached units held to 50 percent of the home's living area, a percentage cap the LMC does not contain. Conversions within existing space (plus 150 sq ft for ingress and egress) have no cap, a JADU is capped at 500 sq ft, and heights are 18 feet detached (20 feet with a roof pitch matching the house) and 25 feet with two stories attached.

State law controls here, not the codified text. LMC 17.41.018.E still requires an owner with legal or equitable title to live on any lot with an ADU or JADU, exempting only ADUs permitted between January 1, 2020 and January 1, 2025 (unless the lot also has a JADU) and JADUs owned by a public agency, land trust or housing organization; that window copies the old 2025 sunset that AB 976 (2023) replaced with a permanent ban, and neither Ord. No. 1130 (2025) nor Ord. No. 1153 (2026) touched the clause. Gov. Code 66315 bars any owner-occupant requirement for an ADU and 66325(a) makes the state article supersede a conflicting local ordinance, so no owner occupancy may be imposed on an ADU permitted today; for JADUs, 66333(b) as amended by AB 1154 requires owner occupancy only when the JADU shares sanitation facilities with the main home, and 66339.5(a) overrides the code's universal JADU rule. The city's 2026 ADU Application and June 2026 FAQ say nothing about owner occupancy, and no city record shows whether staff still apply 17.41.018.E. Separately, owners who take the city's ADU Assistance Loan (up to $10,000, forgivable over five years) must maintain owner occupancy as a loan condition.

LMC 17.41.018.H.1 requires one off-street space per ADU in addition to the main home's parking, as a 10-by-20-foot space in a garage, carport or driveway; tandem driveway parking is allowed, but not in the front setback unless the driveway is at least 20 feet deep. No space is required for an interior (converted) ADU, for an ADU within a half mile walking distance of public transit, which the code defines to include any fixed-route, set-fare bus stop, or for a 'state-exemption ADU' (conversions, JADUs and the detached unit of up to 800 sq ft with 4-foot side and rear setbacks) (H.2.a; 17.41.012.K-L), and the city's 2026 ADU Application applies the space only to ADUs over 850 sq ft outside the transit buffer. Gov. Code 66322(a) adds exemptions the code omits (historic districts, on-street permit areas where the occupant is not offered a permit, a car-share vehicle within one block, and an ADU filed together with a new home that meets one of those tests), and 66314(d)(10) caps any requirement at one space per unit or per bedroom, whichever is less. Garage, carport and covered spaces demolished or converted for an ADU need not be replaced (H.2.b), and state law extends that to uncovered spaces (66314(d)(11)); the code's rule that a JADU carved from an attached garage must replace the lost spaces 'in kind' conflicts with 66334(a), which HCD treated as unlawful additional parking in its July 7, 2026 findings to San Diego County.

ADUs and JADUs that meet Article I need 'only a ministerial building permit' (17.41.014.A), and because the use matrices list them as P they are exempt from site plan review (17.08.050.A; 17.10.050.D.1.f). Since early 2023 ADU applications have been processed by the Building and Safety Division rather than Planning (2025 General Plan Annual Progress Report) on the city's Application for Accessory Dwelling Unit, which the June 2026 FAQ says covers all Planning requirements. The code promises approval or denial within 60 days of a complete application, deemed approval if the city misses the deadline, and written comments with any denial (17.41.014.B-C); the 15-business-day completeness determination and the written appeal decided within 60 business days that Gov. Code 66317 (as amended by SB 543) now requires are not in the code but apply directly. The code shields unpermitted ADUs built before January 1, 2018 from denial on building-standard or ADU-law grounds (17.41.020.B), and Gov. Code 66311.7 now extends that protection to units built before January 1, 2020.

An ADU or JADU 'may be rented' but not for a term shorter than 30 days, whenever it was created (17.41.018.B-C); for state-exempt ADUs (Gov. Code 66323(e)) and JADUs (66333(g)) state law requires terms longer than 30 days, so even a 30-day lease is out for those units. Lancaster has no short-term rental ordinance or registry: the municipal code has no short-term or vacation rental chapter (a code search finds only the SB 9 two-unit rule in 17.41.058), and the council and Planning Commission agendas posted on PrimeGov from 2022 through September 2026 list no short-term rental item, so the 30-day rule is the operative bar on nightly rental of an ADU. An ADU cannot be sold or conveyed separately from the lot and main home except under the qualified-nonprofit path now at Gov. Code 66341 (the code still cites 65852.26), a deed restriction to that effect must be recorded before the building permit issues (17.41.018.F), and the city has not adopted a Gov. Code 66342 ADU-condominium ordinance; when the Planning Commission approved a condominium map for the 16-unit Quail Crossing development on June 15, 2026, Condition 17 tied its 1,236 sq ft ADU to Unit 5. Landlords need a rental housing business license, with periodic inspections, for any rented dwelling unit (Chapter 5.40), and owners who use the city's ADU Assistance Loan must rent the ADU to a low-income household and keep it affordable for at least five years.