Simi Valley | Hillside, Fire and Flood Rules

Simi Valley Hillside, Fire and Flood Rules: Slope Density, Ridgelines, Grading, Fire Zones and Flood Zones

Section 9-32.010 opens: "The City is situated among a series of major and minor hills." Those hills are why Simi Valley has its own Hillside Performance Standards, Chapter 9-32, which cut the number of homes allowed as the land gets steeper, keep buildings off the ridgelines seen from the valley, and limit grading. Fire and flood add two more layers: SB 9 homes in very high fire hazard zones must meet fire construction rules, and Title 7 bans new homes in mapped flood zones. This page sets out all three. The Simi Valley overview gives the short version.

Where the Hillside Rules Apply

Section 9-32.020 applies the standards "to any parcel or any portion of a parcel of land in any land use zone which is located outside of the valley floor boundary line as noted on the Development Map of the Valley Floor." The map is attached to the chapter as Exhibits A and B, which Municode prints as images; this guide did not read them, so ask the Planning Division where a lot sits. Every use the base zone allows stays allowed, subject to the chapter's findings and standards. The purpose is to preserve the hills, promote "single-family, detached housing in hillside areas," keep open space, and protect public safety.

Section 9-32.040 lists 14 exceptions. The ones that matter most to owners:

• A home, additions and accessory buildings on a residential parcel legally subdivided by July 21, 1986, "which does not involve grading for structures on visually prominent ridgelines or on land with a slope in excess of 20 percent or grading in excess of 1,000 cubic yards."
• Any parcel whose only slopes of 10 percent or more are isolated landforms with "a horizontal run of less than 100 feet and a vertical rise of less than 30 feet."
• Lot line adjustments, lot mergers and condominium conversions of existing buildings.
• Rebuilding homes that existed before July 21, 1986 and were destroyed or damaged by fire, earthquake or another natural disaster.
• Fire breaks and fire roads required by the County Fire Department.

Approval requires written findings that the project respects the hills, keeps development off slopes of 20 percent or more except as allowed, lowers density as slope rises, keeps grading "to an absolute minimum," and avoids "mass grading of large pads and excessive terracing." A variance from the chapter follows Section 9-52.090, and a project of four or fewer homes or lots that asks for any deviation needs a Planned Development or Cluster Development Permit.

Homes Allowed by Slope

Source: Simi Valley Municipal Code Sec. 9-32.070, Table 3-3.

Slope is the rise of the land divided by the horizontal run, times 100: a hill that rises 20 feet over 100 feet is a 20 percent slope. Section 9-32.060 requires a slope map "prepared and signed by a registered civil engineer or licensed land surveyor," at a scale of at least one inch to 200 feet, with contours no more than two feet apart (10 feet where the slope is over 20 percent), covering neighboring land within 150 feet. The map sorts the site into bands of 0 to 10, 10 to 15, 15 to 20 and 20 percent or more, with the acres in each. Small isolated slopes under 100 feet of run and 30 feet of rise join the surrounding band, and ravines, ridges and terraces under 150 feet wide in steep areas count as 20 percent or more.

The allowed homes are the sum of each band's acres times its rate in Table 3-3. As a worked example (VanPlex arithmetic), a 10 acre parcel with 4 acres under 10 percent at a 7 per acre General Plan target, 2 acres at 15 to 20 percent and 4 acres at 20 percent or more counts 28 + 0.5 + 0.1 = 28.6 homes. Land that will flood in a 100-year storm, geologic hazard areas without mitigation, and land in an open flood control channel are left out. Homes may be moved to land under 20 percent slope, but hillside sites "shall only be developed with single-family, detached units with a maximum density of seven units per acre." Two exceptions: senior housing, and projects hidden from the valley floor where at least 25 percent of homes are affordable to low and very low income households, capped at 10 homes per gross acre including any bonus.

Table 3-3 contradicts itself on the 10 to 15 percent band, printing "1 unit per 2 acre (2 units per acre)." One home per two acres is 0.5 homes per acre, a quarter of the figure in brackets. The code does not say which controls; ask the Planning Division before relying on either.

Ridgelines and Views

Section 9-32.150 says "there shall be no development along visually prominent ridge lines." Structures may not be built on top of one, and "No point on any structure subject to the provisions of the performance standards shall be closer to a visually prominent ridge line than 150 feet measured horizontally on a topographic map or 50 feet measured vertically on a cross section, whichever is more restrictive," unless the structure sits at or below the lowest visible elevation of the ridge. Homes lost to this rule may move elsewhere on the parcel.

A ridgeline counts if it is visible from the valley floor, which the code defines as "continuously visible for more than 1,000 feet" along the Simi Valley freeway between Kuehner Drive and Oak Park, Madera Road, Tierra Rejada Road, or Kuehner Drive. The City keeps a map of the ridgelines, but "If there should be a conflict between the written provisions of this Section or a detailed site analysis and the map, the written provisions shall control."

Grading, Streets and Buildings

• Grading over 1,000 cubic yards: "No manufactured slope shall exceed 30 feet in height," counting any retaining wall, and none may be steeper than "two horizontal to one vertical." Slopes must be rounded and shaped to look natural, and long cut or fill slopes must curve.
• Drainage: natural drainage courses stay natural where feasible, and interim facilities must allow "no increase in peak runoff from a 10 year storm."
• Streets: local streets are 28 feet curb to curb with five-foot shoulders, a road across slopes over 20 percent may run no more than 100 feet for each home it serves, and residential streets may be no steeper than 10 percent.
• Buildings: "The maximum height of any building constructed on land subject to the standards set forth in this Article shall be two stories or 35 feet, whichever is less." Split-level designs that hide grading under the building are encouraged.
• Landscaping must "reduce fire hazards, stabilize cut/fill slopes, reduce erosion," keep drought-resistant native plants where possible, and favor native trees such as the California Live Oak and Valley Oak.

Sources: Simi Valley Municipal Code Secs. 9-32.060, 9-32.110, 9-32.160 and 9-32.180.

The Director, with the City Engineer, may waive any report when recent reports less than one year old exist, when the reports are part of an environmental document, when the project has "four or fewer residential structures or lots," or when each home sits on five acres or more, off 20 percent slopes, with under 1,000 cubic yards of grading.

ADUs and SB 9 Homes on Hillside Land

Section 9-44.160 says ADUs "proposed in slopes subject to the Hillside Performance Standards ... will be limited to 800 square feet in size," with driveways under Chapter 9-32. Section 9-24.080 limits SB 9 homes "on parcels outside the valley floor" to 800 square feet, and Urban Lot Splits on slopes of 20 percent or more follow the chapter. Government Code 66321 bars a maximum ADU size below 850 square feet, or 1,000 with more than one bedroom, so for ADUs the state floor controls. Government Code 65852.21 lets a city hold an SB 9 home to 800 square feet, so the SB 9 cap stands. The ADUs and SB 9 page has the details.

Fire Hazard Zones

Section 9-24.080 says a Two-Unit Residential Development "shall not be permitted within the Very High Fire Hazard Zones, unless proposed buildings are designed to meet the high fire construction standards adopted or enforced by the City, as determined by the Building Official, the Ventura County Fire District, or the State Fire Marshall, including, but not limited to, any requirement for fire sprinklers." No variance from the fire codes is allowed. An Urban Lot Split is allowed only if the property "is not located within a Very High Fire Hazard Area."

Section 8-26.01 adopts "The California Wildland-Urban Interface Code, 2025 Edition" as a primary building code of the City, through Ordinance No. 1366, in force December 18, 2025. Government Code 51179 requires a city to designate moderate, high and very high fire hazard severity zones by ordinance "within 120 days of receiving recommendations from the State Fire Marshal," and bars it from lowering a zone the State Fire Marshal set. The Simi Valley code read for this guide prints no such designation; its Title 4 fire prevention chapter was repealed in 2008. Check the State Fire Marshal map for the lot. The property tax, fire zones and insurance page explains the state maps.

Flood Zones

Title 7, Chapter 5 applies to every special flood hazard area, "an area having special flood hazards and shown on the Flood Insurance Rate Map (FIRM) as Zone A, AO, AH or AE." The maps are FEMA's study and map dated September 27, 1991 "and all subsequent amendments and/or revisions." Section 7-5.601 prohibits "New construction of any residential or non-residential structures" in those areas, along with basements below the base flood elevation and crawl spaces more than two feet below grade. The Director of Public Works runs the chapter, and any development in a flood area needs a flood area development permit with plans showing 300 feet around the site.

Outside the mapped zones, Section 7-5.602 still applies to development over one-half acre or adding more than 5,000 square feet of hard surface: "The lowest floor elevation of any structures shall be at least one foot above the crown of the nearest street." The code and the SB 9 section differ here. Section 9-24.080 lets SB 9 homes go in the "100 year flood zone" when the Public Works Director approves mitigation, while Section 7-5.601 bars all new residential construction in a mapped flood zone. The code does not say which controls; plan around the Title 7 ban unless the Public Works Director confirms otherwise in writing.

Where to Go Next

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

Frequently Asked Questions

Official sources (checked October 2026)