Fontana | ADUs and SB 9

Fontana ADUs, Junior ADUs and SB 9 Two-Unit Projects

An accessory dwelling unit (ADU) is a second, smaller home on a lot with a main home, with its own kitchen, bathroom and entrance. A junior ADU is a unit of 500 square feet or less built inside a house. An SB 9 two-unit project is two main homes on one lot in a single-family zone. Fontana regulates ADUs in Section 30-467 and SB 9 projects in Section 30-434.1 of the Zoning and Development Code. This page explains both and names each place where the City text is stricter than state law. The Fontana overview sums up the whole guide.

Fontana's ADU Section

Section 30-467 was last amended by Ordinance No. 1983, adopted on February 24, 2026 "to comply with recent changes in State law," according to City Council file 26-0818. Its purpose is to allow ADUs "in compliance with Chapter 13 of Division 1 of Title 7 of the California Government Code," the state ADU law. It applies to every ADU application found complete on or after January 1, 2025; an earlier applicant may choose the old rules in writing.

Every ADU and junior ADU needs an ADU permit and a building permit. Section 30-467(d) says "An ADU permit is considered and approved ministerially, without discretionary review or a hearing." The City has 15 business days to say whether an application is complete and must list any missing items. Once complete, the City must approve or deny within 60 days, or the application is deemed approved, unless the applicant asks for a delay or the ADU comes with a new house that the City has not yet acted on. A denial must list every defect and how to fix it. An applicant may appeal an incompleteness finding or a denial in writing to the City Clerk, and the Planning Commission must decide within 60 business days. A demolition permit for a detached garage being replaced by an ADU is reviewed and issued with the ADU.

Section 30-467(e) sorts ADUs into two classes. Class 1 ADUs are "approved under Government Code § 66323," the list of ADUs a city must approve with no local standards beyond the few the statute names. Class 2 ADUs are "approved under Government Code §§ 66314 through 66322," which let a city set its own standards within state limits.

ADU Types Compared

Sources: Fontana Zoning and Development Code Section 30-467(c), (e) and (g), Supplement 18; City of Fontana ADU Information Sheet, March 2026.

Class 2 ADU Standards

Most new detached ADUs larger than 800 square feet are Class 2. Section 30-467(g) sets the rules:

• Size. Up to 1,200 square feet. An attached ADU on a lot with an existing house is also limited to 50 percent of the house's floor area. No limit from the percentage, floor area ratio, front setback, lot coverage or open space rules "may require the ADU to be less than 800 square feet."
• Setbacks. An 18 foot front setback and 4 foot side and rear setbacks, with no setback for an ADU built in the same place and size as a legal existing structure.
• Lot coverage. The ADU may not push total lot coverage above 50 percent, subject to the 800 square foot guarantee.
• Stories. One story, except that an attached ADU may have up to two stories within the height limit.
• Parking. One space, which may sit in a setback or in tandem, meaning one car behind another. None is needed within one-half mile walking distance of public transit, in an architecturally and historically significant historic district, for a conversion, where on-street permits are required but not offered, within one block of a car share stop, or with a new house that meets one of those tests. Garage spaces lost to an ADU need not be replaced.
• Design. Materials, colors and roof slope must match the house, lights must be down-lights, the ADU needs its own outside entrance, and rooms must be at least ten feet wide in every direction with walls seven feet high.
• Privacy. Windows and doors may not have a direct line of sight to a neighbor. Windows and doors within 30 feet of a property line that is not a street must use clerestory windows six feet above the floor, or frosted or obscure glass.
• Historic sites. An ADU on or within 600 feet of a property on the California Register of Historical Resources must be placed so it cannot be seen from a public street.

Heights in Section 30-467(f)(2) apply to both classes. A detached ADU may be 16 feet, or 18 feet within one-half mile walking distance of a major transit stop or high quality transit corridor, plus two feet to match the house's roof pitch. A detached ADU next to a multifamily building of more than one story may be 18 feet. An attached ADU may be 25 feet or the height limit of the zone, whichever is lower, and no more than two stories.

Junior ADUs and Rules for Every Unit

Section 30-467(c)(6) defines a junior ADU as a unit of "no more than 500 square feet of interior livable space" that is "contained entirely within an existing or proposed single-family structure," including an attached garage. It needs an efficiency kitchen with a cooking appliance, counter and storage, and either its own bathroom or a shared one with an inside door to the house. In line with Government Code 66333, a junior ADU "may only be created on a lot zoned for single-family residences." The owner must live on the property only when the bathroom is shared. A deed restriction, on a form the City provides, must be recorded before the building permit.

Some rules apply to every ADU and junior ADU. No unit may be rented "for a term that is shorter than 30 days." No unit may be sold apart from the lot and main home, except as Government Code 65852.26 allows. Sprinklers are required only if the house has them, and an ADU does not trigger sprinklers in the house. No certificate of occupancy may issue for an ADU before the house's, except after a disaster declared by the Governor on or after February 1, 2025. The City may not deny an ADU because of an unrelated nonconforming condition on the lot, and may not deny legalizing an unpermitted ADU built before January 1, 2020 for building code or ADU rule reasons, unless it is substandard under Health and Safety Code 17920.3.

ADU Fees and Pre-Approved Plans

Section 30-467(h) says "No impact fee is required for an ADU that is less than 750 square feet in size." For larger ADUs, impact fees are charged in proportion to the house: the ADU's floor area divided by the house's floor area, times the fee for a new home. A converted ADU on a single-family lot needs no new utility connection or connection fee unless built with a new house; other ADUs need a separate connection for City utilities. The City's ADU fee sheet, effective January 1, 2023, lists impact fees "APPLIES TO UNITS 750 SF OR GREATER": municipal services $2,630, landscape median $326, public facilities $520, police $552, library $116 and fire $431. Sewer expansion of $7,600 and sewer connection of $1,023 per main home apply only where the ADU connects to City sewer.

The City's Standard ADU Plans page lists three pre-approved detached designs under AB 1332: Morning Glory, 462 square feet with one bedroom; Carnation, 738 square feet with two bedrooms; and Sunflower, 1,143 square feet with three bedrooms. The page says the plans "will require site specific information and permit approval." See the permits and fees page for the rest of the fee schedule.

SB 9 Two-Unit Projects in Fontana

Section 30-434.1 was adopted by Ordinance No. 1877 in December 2021 and amended by Ordinance No. 1885 in February 2022. It allows "the development of two primary dwelling units" on a legally subdivided lot in a single-family residential zone, or a second main home beside an existing one. The Planning Director approves or denies it "ministerially," without discretionary review. Government Code 65852.21 requires a decision within 60 days of a complete application, or the project is deemed approved.

• Who may apply. Only individual property owners, a community land trust or a qualified nonprofit corporation. The applicant must provide a certificate of compliance with the Subdivision Map Act.
• Where. Not on prime farmland, wetlands, hazardous waste sites, protected habitat or conservation land; not in a historic district or on a landmark; and in a very high fire hazard severity zone, earthquake fault zone or flood zone only under the listed conditions.
• Existing housing. No demolition or alteration of housing a tenant occupied in the last three years, rent- or price-controlled housing, or income-restricted housing. No more than 25 percent of an existing home's exterior walls may be removed unless no tenant lived there in the last three years.
• Size and height. Each new main home more than 500 and no more than 800 square feet. On a lot over 2,000 square feet, one story and 16 feet; on a smaller lot, two stories and 22 feet with a five foot stepback above the first floor. No rooftop decks.
• Setbacks. Zone setbacks apply, but they "must yield" so two homes of 800 square feet fit, with at least four feet from side and rear lines. The front setback area must be at least half drought-tolerant landscaping and free of structures over three feet.
• Parking. One space per new home, except within one-half mile walking distance of frequent bus service or a rail or bus rapid transit station, or within one block of a car share location.
• Design and screening. Matching materials, color and roof pitch; down-lights; no direct line of sight to a neighbor; evergreen screening plants at least six feet tall, or a six foot fence.
• Use. Residential only, no rentals under 30 days, no separate sale of the two homes, and the owners must live in one home unless the lot came from an urban lot split.
• Notice. At least 30 business days before construction, the owner writes to the owners of adjacent residential lots. The section says this notice gives neighbors no right to comment.

A lot that did not come from an urban lot split may have a two-unit project "plus any ADU or JADU that must be allowed under state law and the City's ADU ordinance." On a lot from an urban lot split, the total is two homes of any kind. The City may deny a project only if the building official finds in writing a "specific, adverse impact" on public health and safety or the physical environment that cannot be avoided. The lots and subdivisions page covers urban lot splits.

Where City Text and State Law Differ

• The 750 square foot fee line. Section 30-467(h) and the City fee sheet charge impact fees on an ADU of 750 square feet. Government Code 66311.5 bars any impact fee on an ADU "that has 750 square feet of interior livable space or less." The statute controls, so an ADU of exactly 750 square feet pays no impact fee.
• ADUs in R-3, R-4 and R-5. Table 30-430 lists an ADU as not permitted in R-3 under residential uses, and Table 30-446 does the same for R-4 and R-5, while both tables permit ADUs as accessory uses. Government Code 66323 requires approval of converted and detached ADUs on lots with multifamily homes. The statute controls, and Section 30-467(f)(1) itself allows Class 1 ADUs "in a residential or mixed-use zone."
• SB 9 standards that apply only to SB 9 homes. Government Code 65852.21 bars standards "that do not apply uniformly to development within the underlying zone," unless they are more permissive. Fontana's 16 foot, one story cap, the owner-only applicant rule and the screening rules apply only to SB 9 homes, while an R-1 house may be 35 feet. Where they conflict, the statute controls.
• Unfinished template text. Section 30-434.1(e)(6) prints "[Include a lot coverage standard here if desired.]" and "[Include an open space standard here if desired.]" with no standard. The section states no lot coverage or open space number for SB 9 two-unit projects.
• Wrong cross-references. Section 30-467(g)(5) points parking exceptions to "subsection (g)(4)(a)" and defines public transit at "(c)(11)," when the parking rule is (g)(5)(a) and the definition is (c)(12). Section 30-467(f) refers to ADUs approved under "(d)(1) or (d)(2)," which are the permit and fee paragraphs; the classes are in (e)(1) and (e)(2).

Where to Go Next

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

Frequently Asked Questions

Official sources (checked October 2026)