Fontana | Hillside and Fire Zones

Fontana Hillside Overlay and Fire Hazard Zones: Slope Limits, the 2025 Fire Map and SB 9

Fontana has two overlay districts that limit homes on steep or fire-prone land: the hillside overlay and the fire hazard overlay. An overlay is a second layer on the zoning map that adds rules to the base district. This page explains how many homes a sloped lot may hold, how the City's 2025 fire hazard map works, what a fuel modification zone is, and the extra fire rules for SB 9 projects. All rules come from Article IX of the Zoning and Development Code, Supplement 18, and City Council records. The Fontana overview sums up the whole guide.

The Hillside Overlay

Section 30-622 describes the hillside overlay as "A district that protects the public health and safety, minimizes environmental impacts, and requires development to conform to the natural topography of hillside areas." It applies to lots designated in the overlay on the zoning map, "in addition to the provisions in the underlying zoning district," and where the two conflict, the overlay controls (Section 30-630(d)). Its goals include "preserving steep hillsides in open space," limiting earth moved on and off a site, and keeping prominent ridges natural.

Section 30-631 requires a hillside development permit for "All projects within a hillside overlay district and located on a lot with a slope of ten percent or greater," and it covers every kind of permit, from grading and building permits to tentative maps and design review. The Director of Community Development decides when the average natural slope is under 15 percent, cuts or fills are under five feet deep, and earthwork is under 2,500 cubic yards. The Planning Commission decides steeper or larger projects, any fill or cut that would change "a natural drainage channel, blue line stream, waters of the United States, or other watercourse," and anything the Director refers to it.

A hillside application carries more studies than a flat lot. It needs a biotic resources management plan covering plants and animals, impacts and mitigation, with "No net loss of sensitive habitats," plus an archaeological, historic and paleontological report. It also needs a fire management plan with special building standards, such as one-hour rated exteriors, double pane or tempered glass, solid core doors and no combustible gutters, and fuel modification zones: "in the northern area of the City, 300-foot wide zones are required; in the Jurupa Mountains, 200-foot wide zones are required." A fence and landscape plan with fire retardant plants must be approved before any building permit.

Homes Allowed by Slope

Source: Fontana Zoning and Development Code Table 30-633, Supplement 18. Fractions above 0.5 round up.

How the Slope Rules Work

Average slope is the overall steepness of a lot, worked out from a contour map. Section 30-630 gives the formula "Average slope = (0.00229 x I x L)/A," where I is the contour interval in feet, L the combined length of contour lines in feet and A the gross area of the lot in acres. Table 30-633 turns the result into a cap on homes and on grading. By VanPlex arithmetic, a four acre lot with an average slope of 12 percent allows 7 homes and may grade or disturb up to 75 percent of the lot. The same lot at 22 percent allows 2 homes and 25 percent grading. These caps sit on top of the base district: in R-1, for example, the district's 5.0 homes per adjusted gross acre still limits the count.

At 25 percent or more, "No buildings or structures shall be allowed except for fencing, low-water-use landscaping and irrigation systems," and those parts of the lot stay "in a natural condition, without alteration of any sort." An owner may grade only to protect the lot or neighbors from slope failure, fire, earthquake damage or flooding, with a grading permit that shows the need.

Design controls in Section 30-633(b) follow. "No portion or architectural feature of a home shall exceed a height of 25 feet as measured from the natural grade," which matches note (5) to Table 30-434. Buildings must step with the slope, and anyone building or enlarging a structure must show "via a line of sight analysis" that the work does not block the view from an existing home. Retaining walls uphill of a building may be four feet high and downhill walls three feet, with terraces at least three feet apart. Wood fences are not allowed; walls must be masonry, decorative block or river rock.

The 2025 Fire Hazard Map

A fire hazard severity zone is an area the State Fire Marshal rates moderate, high or very high by the fire behavior it expects there. The City's Fire Hazard Severity Zones page says hazard "is based on the physical conditions that create a likelihood and expected fire behavior over a 30 to 50-year period without considering mitigation measures such as home hardening." Under Government Code 51179, a city "shall designate, by ordinance, moderate, high, and very high fire hazard severity zones in its jurisdiction within 120 days of receiving recommendations from the State Fire Marshal."

Fontana did so in Ordinance No. 1972, which "adopts the 2025 Fire Hazard Severity Zone Map as reflected in Exhibit A." The map in Exhibit A is the State Fire Marshal's Local Responsibility Area map for Fontana dated March 24, 2025. City Council file 25-0421 records that the ordinance was introduced by a 3-0 vote on July 8, 2025, and the ordinance was adopted on July 22, 2025, to take effect thirty days later. The staff report for file 25-0340 says the map "identifies areas for inclusion within the northern and southern boundaries of the City."

The same staff report describes what the zones mean for owners. In very high zones, properties must meet the vegetation rules of Government Code 51182, including "maintain[ing] defensible space of 100 feet from each side and from the front and rear of the structure, but not beyond the property line." In high zones, "all new construction or major remodels classified by the Building Official as new construction are required to meet the wildfire resistant construction requirements included in Chapter 7A of the Building Standards Code." Sellers in high and very high zones must make a natural hazard disclosure under Civil Code 1102.19.

Building in the Fire Hazard Overlay

Section 30-656 creates the fire hazard overlay "to provide greater public safety to City residents and structures in areas prone to wildfires." A fuel modification zone is a strip of land between homes and wild land where plants that burn are removed, thinned or replaced with fire-resistant plants. Every tentative tract map, tentative parcel map or design review application in the overlay must include a fuel modification zone plan approved by the Fontana Fire Protection District. Every building permit for a new house or apartment on residential land in the overlay must show the same details, and the zone must be installed before the certificate of occupancy. An addition or rebuild of 50 percent or more of a building brings the whole building under these rules.

• Access. Two points of vehicle access, unless the project sits only on a cul-de-sac or the Fire District approves an emergency-only route with a 26 foot paved surface.
• Cul-de-sacs. Up to 350 feet long, or up to 600 feet with Fire Chief findings and no more than 15 homes.
• Fuel zones. At least 100 feet wide from private side or rear lot lines, on City, homeowners association or easement land, and not on private open space within individual lots unless a fire protection plan allows it.
• Perimeter roads. A fire access road at least 20 feet wide with grades of 14 percent or less, or 12 foot access ways between lots every 350 feet.
• Construction. New buildings must meet Chapter 7A of the California Building Code on "Materials and construction methods for exterior wildfire exposure."
• Fences. Wood or vinyl fences must stay five feet from the nearest building, and side yard gates are required on both sides.

The Fire Chief or Fire Marshal and the Director of Community Development may accept "alternate protection measures" in a fire protection plan for access, cul-de-sac length, fuel zone width and perimeter access, if they give "the same or a greater level of protection." Separately, Fontana adopted the 2025 California Wildland-Urban Interface Code "with no amendments" by Ordinance No. 1975 (Sections 5-615 and 5-616), and Section 11-26 requires sprinklers in new buildings, with an exception for buildings of 500 square feet or less (Section 11-28).

SB 9, Maps and Buyers in Fire Zones

Fontana's SB 9 sections, 30-434.1 and 30-302.1, summarize state law by excluding a lot "Within a very high fire hazard severity zone, unless the site complies with all fire-hazard mitigation measures required by existing building standards." Fontana then adds five measures for an SB 9 lot in a very high zone: direct access to a paved public street at least 40 feet wide that can carry 75,000 pounds, with two separate points of access; dwellings that meet current fire code for very high zones; fire sprinklers in all enclosed structures; every side of every home within a 150 foot hose pull of the street or a hydrant; and, without a pool, "a water reservoir of at least 5,000 gallons per dwelling." Before an urban lot split application, the owner must get a City certificate that the site meets these measures, and pay for the inspection.

For any parcel map in a very high fire hazard severity zone, Section 26-218 requires findings that the subdivision meets state fire safe regulations and that fire protection service will be available. A residential subdivider must also tell buyers of "any known wildfire area within or contiguous to the subdivision" in the buyer package of Section 26-378. The lots and subdivisions page covers maps in full.

Where City Documents Disagree

• Which map applies. Section 30-656(a), as printed in Supplement 18 with Ordinance No. 1972 in its history note, still says the overlay "shall initially be based on the 2008 very high fire hazard severity zones map" and later maps "as deemed appropriate by the City." Ordinance No. 1972 adopts the 2025 map. The adopted ordinance controls.
• A wrong section number. The title of Ordinance No. 1972 amends "Section 30-656(a)," but its Section 3 says it "amends Section 30-626(a)," which is the medical center overlay. The title and the staff report both name Section 30-656(a).
• Alternate measures. Sections 30-656 and 30-658 refer to alternate protection measures "in accordance with the provisions of Section 30-656(e)." Section 30-656(e) covers Fire District standards; the alternate measures are in Section 30-658(e).
• Hillside uses. Section 30-632, the hillside uses section, says uses "shall be permitted in the utility corridor overlay district," a copying error from the utility corridor division.
• State and local areas. The City's Fire Hazard Severity Zones page describes "three levels of hazard in the State Responsibility Areas," while Ordinance No. 1972 adopts the Local Responsibility Area map, which also has moderate, high and very high zones.

Where to Go Next

Related on VanPlex: the property tax, fire zones and insurance page, the SB 9 page and the Fontana overview.

Frequently Asked Questions

Official sources (checked October 2026)