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Diamond Bar · Building on your lot

Building on a hillside in Diamond Bar

Diamond Bar's own rules on building on a hillside, with the code text for every value.

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

What Diamond Bar's code says

Diamond Bar code What Diamond Bar's code adds
Grading and retaining walls
  • Finished slopes may be no steeper than 50% (2:1).
    Applies: Hillside lots.
    § 22.22.080 · code text
    Finished slopes shall not be created greater than 50 percent (2:1) except adjacent to a structure where the created slope is limited to a maximum of 67 percent (1.5:1).
  • Finished slopes may be no steeper than 67% (1.5:1).
    Applies: Hillside lots, next to a structure.
    § 22.22.080 · code text
    Finished slopes shall not be created greater than 50 percent (2:1) except adjacent to a structure where the created slope is limited to a maximum of 67 percent (1.5:1).
  • Retaining walls may be no higher than 4 feet.
    Applies: Retaining walls for lot pads on hillside lots.
    § 22.22.080 · code text
    Retaining walls associated with lot pads shall not exceed four feet in height.
  • One side-yard retaining wall up to 42 inches high is allowed.
    Applies: Hillside lots sloping with the street, where necessary.
    § 22.22.080 · code text
    On lots sloping with the street, and other configurations not discussed above, one retaining wall, not to exceed 42 inches in height, may be used in a side yard where necessary.
When hillside rules apply
  • Hillside rules start at a 10% natural slope.
    Applies: Natural slopes of 10% to 24.9%, not landform graded, need special hillside design that minimizes grading.
    § 22.22.070 · code text
    1. | 10% to 24.9% | Special hillside architectural and design techniques that minimize grading are required in this slope category.

Who this affects

HomeownersContractorsDesigners

Frequently asked questions

What extra rules apply to a hillside lot in Diamond Bar?

Diamond Bar's code: Hillside rules start at a 10% natural slope. (Natural slopes of 10% to 24.9%, not landform graded, need special hillside design that minimizes grading.) (§ 22.22.070); Finished slopes may be no steeper than 50% (2:1). (Hillside lots.) (§ 22.22.080).

General information, not legal advice.

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Ask GoCodebook how Diamond Bar's building on a hillside rules apply to your situation and get an answer that cites the section.

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Diamond Bar Municipal Code — full text