Fremont | ADUs and SB 9

Fremont, California ADUs and SB 9: ADU Sizes, Heights and Setbacks, Junior ADUs, Two-Unit Developments, Permits and Fees

An accessory dwelling unit (ADU) is a second home on a lot that already has, or will have, a main home. A junior ADU (JADU) is a unit of 500 square feet or less inside a house. Fremont keeps its rules for both in one section of the Municipal Code, 18.190.005, and its rules for SB 9 projects in the next one, 18.190.007. The City Council last amended both on May 5, 2026, so the published text is recent. In 2025 the City issued building permits for 177 ADUs, 32 percent of all the homes permitted that year. This page covers what each section allows, where it differs from state law, and the fees. The Fremont overview has the summary.

ADU Types and Limits

Source: Fremont Municipal Code, Section 18.190.005, subsections (c), (d) and (e), as amended by Ordinance 02-2026 of May 5, 2026. Sizes are interior livable space.

The purpose line of the section says it exists "to implement Cal. Gov't Code §§ 66310 through 66342 by allowing the creation of accessory dwelling units (ADUs) and junior accessory dwelling units (JADUs) through ministerial review." Ministerial review means staff check an application against fixed rules, with no hearing and no judgment about design. The section also says which text controls in a conflict: "In the event of a conflict between the provisions of this section and the California Government Code, including without limitation Cal. Gov't Code §§ 66314 through 66332, as may be amended, the provisions of the applicable Government Code shall prevail." The state rules are on the California ADU law page.

Where an ADU Is Allowed and How Many

• Where. "An ADU may be constructed on the same lot as an existing or proposed single-family or multifamily dwelling in residential or mixed-use zoning districts, as well as planned districts and planned unit developments that allow residential uses." The residential use table lists ADUs as an accessory use in R-1, R-2, R-3 and R-G.
• The general count. "no more than one ADU shall be permitted to be located on the same lot that has an existing or proposed single-family dwelling. An ADU and JADU may be located in the same primary dwelling."
• The statewide exemption. Subsection (e) follows Government Code 66323 and allows these units "or any combination" of them on a house lot: "One ADU and one JADU per lot with an existing or proposed single-family dwelling" inside the house or an accessory structure, and "One detached, new construction ADU" that does "Not exceed a total floor area of 800 square feet of livable space." Together that is a house, a converted ADU, a junior ADU and a small detached ADU.
• Density. "An ADU and/or a JADU shall not count toward the allowed density for the lot upon which the ADU and/or the JADU is located."
• Types. An ADU may be attached to or inside the main home, "including attached garages, storage areas or similar uses, or an accessory structure," or detached, "including detached garages."
• Separate entrance and address. "An ADU shall provide at least one exterior entrance that is separate from the main entrance of the primary dwelling. An ADU shall also provide a separate address from the primary dwelling."

Size, Height and Setbacks

• Converted space. "An ADU converted from existing floor area shall not be subject to any size limitations," and it has no height limit and no setback. The same holds for an ADU "that replaces an existing structure and is in the same location and to the same dimensions as the structure being replaced." An expansion of up to 150 square feet is allowed where needed for entry and exit.
• New attached ADU. "The total floor area for an attached ADU (new addition) created from new floor area shall not exceed 1,000 square feet of interior livable space."
• New detached ADU. "The total floor area for a detached ADU (new structure) created from new floor area shall not exceed 1,200 square feet of interior livable space."
• What is left out of the count. The calculation "shall not include garages, carports, covered porches/patios, breezeways, and/or other accessory structures."
• Height of an attached ADU. "30 feet or the building height limitation of the underlying zoning district that applies to the single-family dwelling, whichever is lower." The state floor in Government Code 66321 is 25 feet, so the City allows more than the statute requires.
• Height of a detached ADU. 16 feet. Within "one-half mile walking distance of a major transit stop or a high-quality transit corridor," 18 feet, and "An additional building height of two feet shall be allowed to accommodate a roof pitch on the ADU that is aligned with the roof pitch of the single-family dwelling."
• Roof pitch. "No minimum or maximum roof pitch is required for an ADU."
• Setbacks. "A side and rear yard setback of four feet shall be required for attached and detached ADUs created from new floor area." The front yard setback of the main home applies, "unless such a requirement would preclude the construction of an ADU described in subsection (e)."
• Rooftop decks. "Rooftop decks on ADUs are prohibited." The staff report for Ordinance 02-2026 lists this change as "Prohibit rooftop decks on top of ADUs for neighbor privacy."
• Fire sprinklers. "The installation of fire sprinklers shall not be required for an ADU or JADU if fire sprinklers are not required for the primary dwelling unit."

Parking, Owner Occupancy, Rental and Sale

• Parking. "No additional parking spaces shall be required for an ADU. Additionally, no replacement parking shall be required when a covered or uncovered parking space is demolished in conjunction with the construction of an ADU or converted into an ADU." The waiver applies to every ADU in the city.
• Owner occupancy. "Owner occupancy shall not be required for either the primary dwelling unit or the ADU."
• Rental. "An ADU and/or a JADU shall not be rented for a term of less than 30 days."
• Sale. "an ADU may be rented separate from the primary residence; however, the ADU shall not be sold or otherwise conveyed separate from the primary residence," except as Government Code 66341 provides.
• Utilities. An ADU inside the existing or proposed space of a home or accessory structure "shall not be required to install a new or separate utility connection directly between the ADU and the utility nor shall a related connection fee or capacity be charged unless the ADU is proposed to be constructed with a new primary dwelling."
• Existing zoning problems. Correcting nonconforming zoning conditions "which do not present a threat to public health and safety and are not affected by the construction of an ADU and/or a JADU, shall not be required as a condition for ministerial approval."
• Rent review. Fremont's rent review chapter covers ADUs that are rented. Section 9.60.050 exempts "junior accessory dwelling units" and shared housing units, and it does not list ADUs among the exemptions.

Junior ADUs

Subsection (d) holds the junior ADU rules, and it defers to Government Code 66333 and the sections after it in any conflict.

• Number and size. "Excluding an ADU, no more than one JADU shall be allowed." It is "limited to a maximum size of 500 square feet of interior livable space and contained entirely within a single-family residence, including an attached garage."
• Where. "on a residential lot zoned for single-family residences within the walls of a single-family residence built, or proposed to be built, on the lot."
• Entrance. At least one exterior entrance separate from the main entrance of the house, and a separate address.
• Owner occupancy. "If the JADU has shared sanitation facilities with the existing structure, owner-occupancy in the single-family residence in which the JADU is located shall be required." The owner may live in either part. "Owner-occupancy shall not be required if the JADU has separate sanitation facilities, or if the owner is another governmental agency, land trust, or housing organization."
• Deed restriction. The owner records a deed restriction with "A prohibition on the sale of the JADU separate from the sale of the single-family residence" and a limit on its size and features.
• Fire rules. "For the purposes of any fire or life protection, a JADU shall not be considered a separate dwelling unit."

ADUs on Apartment and Townhome Lots

• Conversions. "A minimum of one ADU and a maximum of 25 percent of the total number of existing multifamily dwelling units shall be permitted to be converted from existing multifamily dwelling structures that are not used as livable space, including, but not limited to, storage rooms, boiler rooms, passageways, attics, basements, or garages." A 20-unit building could add five (VanPlex arithmetic: 25 percent of 20).
• Detached. "No more than eight detached ADUs shall be permitted on a lot that has an existing multifamily dwelling. However, the number of accessory dwelling units allowable pursuant to this clause shall not exceed the number of existing units on the lot. No more than two detached ADUs shall be permitted on a lot that has a proposed multifamily dwelling."
• Height. 16 feet, or 18 feet near major transit or where the lot has "an existing or proposed multifamily, multistory dwelling."
• Sprinklers. "The construction of an ADU or JADU shall not trigger a requirement for fire sprinklers to be installed in an existing multifamily dwelling."

ADUs are part of new projects too. The Planning Commission agenda of February 26, 2026 lists a 24-unit detached townhome project on Dusterberry Way with "21 attached accessory dwelling units."

The ADU Permit

• Completeness. An application "shall be determined to be complete or incomplete and written notice of this determination to the applicant shall be provided not later than 15 business days after the receipt of the application." An incomplete notice must list the missing items.
• The 60-day rule. "A permit shall be issued within 60 days of submission of a complete application for an ADU and/or a JADU conforming to the provisions of this section if there is an existing single-family or multifamily dwelling on the same lot." Government Code 66317 adds that if the agency has not acted within 60 days, "the application shall be deemed approved."
• With a new house. The City "may delay acting on the permit application for that ADU and/or JADU until the city acts on the permit application to create or serve the new single-family or multifamily dwelling."
• Design review. Section 18.235.020 lists "Accessory dwelling units when consistent with Section 18.190.005" under ministerial design review, and a note to the use table says "A ministerial design review permit may be required."
• Building permit. "All ADUs and/or JADUs, including those that are internal to an existing structure and converted from existing floor area, require a building permit."
• Appeal. "If a permit application is determined to be incomplete or denied, the applicant shall be able to appeal the decision using the process specified in Chapter 18.300." An appeal must be filed within 10 calendar days.
• Historic properties. An ADU with exterior changes to a structure listed in the California Register of Historical Resources must follow the federal Standards for the Treatment of Historic Properties and the City's Objective Design Standards for Eligible Potential Register Resources, which the City adopted in 2025 according to the April 2026 staff report.

ADU Fees

The Master Fee Schedule, Section II, effective January 5, 2026 lists two Planning lines for these units. Under Design Review, Limited Review, "ADU/JADU, new only" has a $2,000 deposit. Under Conformance Plan Check, "ADU/JADU" has a $1,000 deposit. Both have the fee basis "Job Cost," which means staff time is charged against the deposit. Building permit and plan check fees are separate.

• Impact fees. Government Code 66311.5 bars any impact fee on "an accessory dwelling unit that has 750 square feet of interior livable space or less or a junior accessory dwelling unit that has 500 square feet of interior livable space or less." For a larger ADU, impact fees "shall be charged proportionately in relation to the square footage of the primary dwelling unit." Fremont's impact fee table is set by bedroom count and has no ADU line, so ask the City how it applies the proportional rule.
• Affordable housing fee. Chapter 18.155 leaves ADUs out. "No affordable housing fee shall be imposed on accessory units and density bonus units," and building an ADU under Section 18.190.005 "shall not be considered a rental project."
• Service fees. The City "may charge a fee covering the costs associated with the issuance of the design review permit, building permits, and related inspections."

ADU Permits in Numbers

The City Council staff report of March 10, 2026 on the 2025 Annual Progress Report says: "In 2025, the City issued building permits for 177 ADUs." It counts 549 new housing units with building permits that year, and says ADUs "made up approximately 32-percent (177 units) of the total issued permits." The 2024 figure was 133. The report adds that the City's housing plan "estimated an annual projection of 60 ADUs each year," a figure passed in each year of the plan period so far. For state reporting, the 177 units were assigned to income groups using a regional survey: 53 very low, 53 low, 53 moderate and 18 above moderate income.

A Guesthouse Is a Different Thing

The R-1 district also allows a guesthouse as an accessory use. A guesthouse is a separate category from an ADU and carries tighter limits. Section 18.190.205 says "Guesthouses shall not exceed 600 gross square feet in area," "shall contain no kitchen or cooking facilities, including but not limited to microwave ovens, hot plates, and toaster ovens," and "shall not be separately rented, let or leased from the main residence." A guest may stay for no more than three months in a calendar year. A detached guesthouse must be at least five feet from the property line, and the owner records a notice of these limits before the building permit is issued. An owner who wants a rentable unit with a kitchen applies for an ADU.

SB 9 Two-Unit Developments

SB 9 is the 2021 state law that makes a city approve two homes on a lot in a single-family zone, and a split of that lot, with no hearing. The two-unit rule is Government Code 65852.21. Fremont's Section 18.190.007 states its own purpose as to "Provide objective zoning standards for two-unit developments and urban lot splits within single-family residential zones."

Source: Fremont Municipal Code, Section 18.190.007, subsections (d) and (e), as amended by Ordinance 02-2026 of May 5, 2026.

• What counts. A two-unit development is "a development that proposes no more than two new units or proposes to add one new unit to one existing unit."
• The four-unit cap. "For a parcel where an urban lot split is not proposed or approved, no more than a total of four units of any kind, including accessory dwelling units and junior accessory dwelling units, shall be constructed or maintained."
• Standards. The project must meet the objective zoning, subdivision and design standards of its district, but the zoning administrator "shall modify or waive any standard if the standard would have the effect of physically precluding the construction of two units on either of the resulting parcels created pursuant to this section or would result in a unit size of less than 800 square feet."
• Larger units. A project that goes beyond the minimum size in the statute "shall be subject to the development standards, including but not limited to setbacks, height, size, and second-story square footage, applicable to the parcel as provided in the zoning district."
• Parking. "One parking space shall be required per unit," with no parking where the parcel is within one-half mile walking distance of a major transit stop or a high-quality transit corridor stop, or where "There is a designated parking area for one or more car-share vehicles within one block of the parcel."
• Separate utilities. "The proposed dwelling units shall provide a separate gas, electric and water utility connection directly between each dwelling unit and the utility."
• Tenants. If existing housing would be altered or demolished, the owner signs an affidavit that it is not rent-restricted housing and not "Housing that has been occupied by a tenant in the last three years."
• Historic sites. A two-unit development may not be located in "a contributing structure within a historic district" or on a site listed as a city landmark or historic property.
• Denial. The building official may deny a project only on a written finding of "a specific, adverse impact upon public health and safety for which there is no feasible method to satisfactorily mitigate or avoid."
• Covenant. Before the final building inspection the owner records a covenant limiting the property to residential uses and barring rentals "for a period of less than 30 days."

The lot split half of SB 9 is on the lot size and subdivisions page.

Two Fremont Rules That Add Cost to SB 9

• Impact fees. "Two-unit developments are subject to the city's impact fee ordinance, Chapter 18.290." The fee table is on the permits and fees page.
• The affordable housing ordinance. A two-unit development that meets the definition of a residential project in Chapter 18.155 "shall be subject to the city's affordable housing ordinance (Chapter 18.155), as may be amended." Section 18.155.020 defines a residential project as "any project containing two or more net new living units or residential lots." A project that adds one unit to an existing home is under that count.
• What the ordinance asks of a rental project. Section 18.155.030: "at least 10 percent of all living units shall be made available at an affordable cost to low income households," and "If the fraction is below 0.5, no additional unit nor fee is required for the fractional unit." Ten percent of two units is 0.2 (VanPlex arithmetic).
• What it asks of a for-sale project. Fifteen percent of the units, and "For fractions of affordable units required in for-sale projects, the developer may either construct an additional affordable unit or pay an affordable housing fee for the fractional unit." The fee schedule lists the for-sale in-lieu fee at $44.00 per habitable square foot.

How the City applies these lines to a two-home project was not found in the documents read. Ask the Housing Division for a written answer before pricing a project.

The March 10, 2026 staff report gives the counts. "In 2025, eleven SB 9 applications were submitted to the City," and the City approved nine. Two of the applications submitted and five of those approved were two-unit developments. Three building permits were issued in 2025 for homes applied for under SB 9.

Where the Code, City Documents and State Law Differ

• Attached ADU size. Government Code 66314 says that where there is an existing main home, "the total floor area of an attached accessory dwelling unit shall not exceed 50 percent of the existing primary dwelling." Section 18.190.005 gives a flat 1,000 square feet and has no 50 percent line. The section says the Government Code prevails in a conflict. Ask the City which figure it applies to a small house.
• An old statute number. The utility connection clause cites "Cal. Gov't Code § 66324(d)." The Legislature renumbered Section 66324 as Section 66311.5 effective January 1, 2026. The rule is the same.
• When the ADU ordinance was amended. The March 2026 staff report refers to "the City amending its ADU Ordinance in Fall 2023." The history note under Section 18.190.005 lists Ordinance 06-2023 of July 11, 2023, then Ordinance 01-2025 and Ordinance 02-2026.
• SB 9 in R-2. The use table permits two-unit developments in R-1 and marks them as prohibited in R-2, R-3 and R-G. Section 18.190.007 itself speaks of "a single-family residential zone or a planned district that allows single-family residential units."
• A statute number in the staff report. The March 2026 report cites "Government Code §§ 65851.21" for two-unit developments. The statute is Section 65852.21, which the code cites correctly.

Limits of This Page

The code text is the publisher's copy, current through Ordinance 02-2026 of May 5, 2026. City Council agendas were read through October 6, 2026 and show no later change to either section. The City website answered 403 to a script, so the City's ADU handouts, application forms, SB 9 forms, the Citywide Design Guidelines and the objective standards for historic resources were not read. Building permit fees for a specific ADU, school fees, and water and sewer charges from the Alameda County Water District and the Union Sanitary District are not given. Whether a lot is within one-half mile walking distance of a major transit stop depends on its location; ask the Planning Division.

Where to Go Next

Related on VanPlex: the Fremont overview, the California ADU law page and the California SB 9 page.

Frequently Asked Questions

Official sources (checked October 2026)