ADU rules in Fremont

Detached ADUs, including converted detached garages, are allowed with an existing or proposed single-family or multifamily dwelling in residential and mixed-use districts and in planned districts and planned unit developments that allow residential use (FMC 18.190.005(c)(1), (c)(3)); Table 18.90.080 lists ADUs as accessory uses in R-1, R-2, R-3 and R-G, noting that a ministerial design review permit may be required. On the local track a single-family lot gets one ADU (new detached units up to 1,200 sq ft, 16 ft tall, 4-ft side and rear setbacks) plus a JADU, while the statewide-exemption track in 18.190.005(e) separately guarantees one new detached unit of up to 800 sq ft in combination with a conversion ADU and a JADU (Gov. Code 66323(a)). On a lot with an existing multifamily building up to eight detached ADUs are allowed, never more than the number of existing units, and two on a lot with a proposed multifamily building (18.190.005(e)(4), conformed to SB 1211 by Ord. 02-2026). In the O-S open space district ADUs are accessory uses in the General, Hill (beyond Ridgeline), Hill Face and Hillside (Measure A) designations but prohibited in the City Park, Private and Resource Conservation/Public designations (Table 18.55.110).

ADUs attached to or located within the primary dwelling, including attached garages, storage areas and accessory structures, are allowed on the same lots as detached units (FMC 18.190.005(c)(1), (c)(3)). Conversions of existing floor area have no size or height limit and need no setback, with up to 150 sq ft of expansion allowed for ingress and egress; new-floor-area attached additions are capped at 1,000 sq ft of interior livable space and 30 ft or the zoning district's height limit, whichever is lower (18.190.005(c)(4) to (c)(6)). A JADU of up to 500 sq ft may also be created within a single-family residence (an attached garage counts), one per lot, and an ADU and a JADU may sit in the same primary dwelling (18.190.005(c)(2)(A), (d)).

New detached ADUs are capped at 1,200 sq ft and new attached additions at 1,000 sq ft, both measured as interior livable space and excluding garages, carports, covered porches and patios, breezeways and other accessory structures, while ADUs converted from existing floor area have no size limit (FMC 18.190.005(c)(4)). Fremont uses the flat 1,000 sq ft attached cap rather than the 50 percent of the primary dwelling measure in Gov. Code 66314(d)(4), and both caps clear the 850 and 1,000 sq ft floors of Gov. Code 66321(b)(2). Detached units are limited to 16 ft, or 18 ft within one-half mile walking distance of a major transit stop or high-quality transit corridor (plus 2 ft for a roof pitch matching the main house) or on a lot with a multistory multifamily building; attached units may reach 30 ft or the zoning height limit, whichever is lower, and Ord. 02-2026 struck the old two-story cap, added that no minimum or maximum roof pitch is required, and banned rooftop decks on ADUs (18.190.005(c)(4)(C), (c)(5)). Side and rear setbacks are 4 ft, and the primary dwelling's front setback applies unless it would preclude an 800 sq ft state-exempt unit (18.190.005(c)(6)). JADUs are limited to 500 sq ft of interior livable space (18.190.005(d)(2)).

Owner occupancy is not required for either the primary dwelling or the ADU (FMC 18.190.005(c)(9)), consistent with the bar on owner-occupancy conditions in Gov. Code 66315. For JADUs, Ord. 02-2026 (effective 6-4-2026) replaced the old universal owner-occupancy clause: the owner must live on site (in either the main portion of the house or the JADU) only when the JADU shares sanitation facilities with the residence, and never when the owner is a governmental agency, land trust or housing organization (18.190.005(d)(5)), matching Gov. Code 66333(b) as amended by AB 1154. The city's January 2026 handout states the same shared-bathroom rule.

No additional parking spaces are required for an ADU, and no replacement parking is required when a covered or uncovered parking space is demolished for, or converted into, an ADU (FMC 18.190.005(c)(14); Ord. 02-2026 broadened the old 'garage, carport, or covered parking structure' wording to any covered or uncovered space). Table 18.183.030 lists an accessory dwelling unit at 0 covered, 0 uncovered and 0 guest spaces, so the rule applies citywide rather than only in the transit, historic-district and other exemption areas of Gov. Code 66322. Because 18.190.005(c) prevails over other code sections, general rules such as the hillside on-site parking requirement in 18.130.090 do not reach ADUs. JADUs likewise need no spaces, though Table 18.183.030 adds that the primary dwelling must meet all applicable standards (see caveats).

Any ADU or JADU application that meets the location and development standards gets ministerial review and approval without discretionary review or a public hearing, with a written completeness determination within 15 business days and a permit within 60 days of a complete application when a dwelling already exists on the lot (FMC 18.190.005(b)(4), mirroring Gov. Code 66317). In practice an ADU needs a ministerial design review permit (18.235.020(a)(4)(B); the zoning administrator may delegate it to staff under 18.235.040(a)(1)), a building permit (18.190.005(b)(5)) and a new address, which the city processes concurrently on request through Accela Citizen Access; the ADU must be permitted separately from any work on the main house. Incompleteness determinations and denials are appealable under Chapter 18.300, and preapproved plans get a 7-business-day review instead of 15 per the city's preapproved ADU page.

ADUs and JADUs may be rented separately from the main house but not for terms under 30 days (FMC 18.190.005(b)(6), (c)(12)); Gov. Code 66315 allows a 30-days-or-longer requirement, while 66323(e) and 66333(g) direct cities to require terms longer than 30 days for state-exempt ADUs and JADUs, and 18.190.005(c) and (d) defer to the Government Code where the texts conflict. Short-term rentals (under 30 consecutive days) need a city permit under Chapter 5.100 (Ord. 01-2024, effective 2-8-2024), are allowed only in the host's primary residence and only in primary dwelling units, and are expressly not permitted in ADUs, JADUs, guest houses or SB 9 units (5.100.040(a)). An ADU cannot be sold or conveyed separately except through a qualified nonprofit under Gov. Code 66341; Fremont has not opted into the Gov. Code 66342 ADU-condominium regime, and a JADU carries a recorded deed restriction against separate sale (18.190.005(d)(6)). Long-term ADU tenancies also fall under the city's Rent Review Ordinance (Chapter 9.60: rent-increase notice rules, one increase per 12 months, non-binding review of increases above 5 percent), which exempts JADUs.