Fremont's Accessory Structures: The Rules That Matter

Every city handles accessory structures a little differently. In Fremont, California, there are 6 distinct rules that residents and property owners should be aware of. Some are stricter than what neighboring cities enforce, and others are more relaxed. Here is what you need to know.

Tiny Homes

Fremont adopted Appendix BB (Tiny Houses) of the 2025 California Residential Code under Municipal Code Sec. 15.47.030(a), letting detached tiny houses built as accessory structures use the appendix's reduced ceiling-height, egress, stair and loft standards instead of full dwelling rules, while still requiring a standard building permit.

Key details: Governing appendix: 2025 CRC Appendix BB (Tiny Houses). Adopting section: Municipal Code Sec. 15.47.030(a). Permit required: Yes, through Building and Safety Division. First-violation fine: Up to $130 (Sec. 1.15.020(c)(1)). Effective date: November 18, 2025 (Ord. 13-2025).

Constructing a tiny house without the required building permit, or in violation of Appendix BB's adopted standards, is enforced under Fremont's Title 15 penalty schedule at Municipal Code Sec. 1.15.020(c): infractions carry a fine up to $130 for a first violation, up to $700 for a second within a year, and up to $1,300 for each further violation of the same requirement within that year. A cited owner can appeal a second- or third-violation fine to the building official in writing within 10 calendar days.

ADU Rules

Fremont approves accessory dwelling units ministerially under Municipal Code Section 18.190.005, with no discretionary hearing. Detached ADUs top out at 1,200 square feet and 16 feet tall (18 feet near major transit), require only a four-foot side and rear setback, and cannot be rented for less than 30 days.

Key details: Governing section: FMC 18.190.005. Detached ADU max size: 1,200 sq ft (new construction). Detached ADU max height: 16 ft (18 ft near transit). Setback (new floor area): 4 ft side and rear. Permit timeline: 60 days after complete application.

Renting an ADU or JADU for a stay under 30 days violates Section 18.190.005(b)(6) and can trigger code enforcement action under the city's general municipal code enforcement provisions, since the unit is treated as a short-term rental use the zoning code does not permit. Constructing an ADU without the required building permit, mandatory under 18.190.005(b)(5) even for interior conversions, exposes the property owner to stop-work orders and after-the-fact permit fees, and selling a JADU separately from the main residence breaches the recorded deed restriction the city requires at approval.

ADU Rental Restrictions

Fremont bars short-term rental of accessory dwelling units and junior ADUs. Under Municipal Code Sec. 18.190.005(b)(6), an ADU or JADU cannot be rented for a term of less than 30 days, closing off vacation-rental use of these units citywide.

Key details: Minimum rental term: 30 days. Governs: ADUs and JADUs alike. Applies to: All ministerially permitted units. Separate sale: Prohibited apart from primary home. Enforcement: Chapter 18.15 code enforcement.

The city's community development and code enforcement staff handle ADU compliance complaints, typically triggered by neighbor reports of a unit listed on a short-term rental platform. Because Chapter 18.190 sets the standard as a condition of the ministerial permit itself, a documented violation can be treated as a zoning code violation subject to Chapter 18.15 enforcement, which can include a correction notice, administrative citation, and civil penalties for a continuing violation until the short-term use stops.

ADU Owner Occupancy

Fremont does not require the property owner to live on site to build or keep an accessory dwelling unit. Municipal Code Sec. 18.190.005(c)(9) states owner occupancy is not required for either the primary dwelling or the ADU.

Key details: Owner-occupancy required for ADU: No. Owner-occupancy required for primary home: No. Governing subsection: 18.190.005(c)(9). JADU treatment: Separate state rules may apply. Permit review type: Ministerial, no hearing.

Because owner occupancy is not a permit condition for ADUs under this section, there is no occupancy-based violation for the city to enforce against an ADU owner who lives elsewhere. Code enforcement action under this chapter instead attaches to other conditions of the ministerial permit, such as unpermitted construction, exceeding the size or height limits, or renting the unit for under 30 days, which the planning division and building division handle through standard zoning code enforcement.

If you are coming from a city with tighter rules, you will find Fremont gives residents more flexibility on adu owner occupancy.

ADU Impact Fees

Fremont exempts accessory dwelling units from development impact fees when the ADU is built as a remodel or addition that does not change the use of the property. The exemption sits in the city's impact fee ordinance, Chapter 18.290, alongside the broader fee protest and credit system.

Key details: Governing section: FMC § 18.290.110(b). Exemption scope: ADU remodel/addition, no change of use. Fee types covered: Traffic, capital facility, fire, park fees. Administering office: Community Development Director. Related credit dates: 1989/1991/1972 razed-structure cutoffs.

There is no separate ADU impact-fee violation provision; the exemption in Section 18.290.110(b) simply removes the fee obligation for qualifying remodels or additions. If a project does trigger a change of use, standard Chapter 18.290 fee collection applies: no city official may issue a certificate of occupancy or allow occupancy of a unit until the fee is paid or a recorded deferral agreement under Section 18.290.070(c) is in place, and the city may recover its costs of enforcement and collection, including attorneys' fees, under any such agreement.

The rules around adu impact fees in Fremont lean permissive, but that does not mean anything goes.

Shed & Carport Rules

Fremont caps detached accessory structures like sheds at 12 feet in height and 30 percent lot coverage of the required yard. Small sheds under 120 square feet and 6.5 feet tall can skip the standard setback rules entirely under Municipal Code Section 18.153.040.

Key details: Max height (standard): 12 feet. Exempt shed height: 6 feet 6 inches. Exempt shed size: 120 sq ft or less. Lot coverage cap: 30% of required yard. Setback from property line: 5 feet (exterior wall).

Sheds and other accessory structures built without meeting Chapter 18.153's setback, height, coverage or separation standards are subject to code enforcement action under the city's zoning enforcement authority in Title 18, which can require the structure to be relocated, modified or removed. Structures that exceed 120 square feet generally require a building permit before construction; building without one exposes the owner to permit-after-the-fact fees on top of any zoning correction.

The Bottom Line

Compared to many U.S. cities, Fremont gives residents more room on accessory structures. 2 of the 6 rules here are rated permissive. But permissive does not mean unregulated. There are still requirements, and the city does enforce them when violations are reported.

These rules come from Fremont's publicly available municipal code. For complete penalty schedules, exemption details, and answers to common questions, see the individual ordinance pages throughout this guide.