Building on a hillside in Sonora: the local rules

Each rule below links to the section of the Sonora Municipal Code it was read from, with the code text one click away (checked October 2026). General information, not legal advice.

What Sonora's code says

Sonora code What Sonora's code adds
Grading and retaining walls	Cut slopes disturbing 15 feet or more of width must be retained at the toe, limiting disturbance to 15 feet. Applies: Hillside development: cut slopes. The width is the horizontal disturbed earth area. § 17.34.100 · code text Where cut slopes will produce a horizontal disturbed earth area of fifteen feet or more in width, they shall be retained at the toe of the slope so that the horizontal disturbed earth area is no more than fifteen feet in width. Fill slopes should be no steeper than 2:1. Applies: Hillside development. Slopes with a 5-foot horizontal distance may be 1½:1 if a geotechnical report or appearance justifies it. § 17.34.100 · code text Fill slopes should not be steeper than 2:1 except for slopes that have a horizontal distance of five feet, which may be 1-1/2:1 when justifiable in a geotechnical report and/or when aesthetically justifiable. Fill slopes disturbing 15 feet or more of width must be retained at most 15 feet from the slope top. Applies: Hillside development: fill slopes. § 17.34.100 · code text Fill slopes producing a horizontal disturbed earth area of fifteen feet or more shall be retained at a point fifteen feet (maximum) from the top of the slope.
When hillside rules apply	Hillside rules apply at an average slope of 10% or more. Applies: New homes: at most 6 units per gross acre on 10-15% slopes, fewer on steeper slopes. § 17.34.130 · code text L = the combined length in feet of all contour lines within that portion of the project site with slopes of 10% or greater

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Frequently asked questions

What extra rules apply to a hillside lot in Sonora?

Sonora's code: Hillside rules apply at an average slope of 10% or more. (New homes: at most 6 units per gross acre on 10-15% slopes, fewer on steeper slopes.) (§ 17.34.130); Cut slopes disturbing 15 feet or more of width must be retained at the toe, limiting disturbance to 15 feet. (Hillside development: cut slopes. The width is the horizontal disturbed earth area.) (§ 17.34.100).

Building on a hillside in Sonora

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