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Contra Costa County · Building on your lot

Building in a flood zone in Contra Costa County

Contra Costa County's own rules on building in a flood zone, with the code text for every value.

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

What Contra Costa County's code says

Contra Costa County code What Contra Costa County's code adds
Floodplain permit
  • A county public works floodplain permit is needed before construction, a grading or building permit, or any development.
    Applies: Property in any special flood hazard area.
    § 82-28.802 · code text
    A floodplain permit shall be obtained from the Contra Costa County public works department before construction, and prior to issuance of a grading permit or building permit, or commencement of development on any property within any area of special flood hazards established in Section 82-28.604.
Height of the lowest floor
  • At or above base flood elevation plus 2 feet in the San Francisco Bay Delta Estuarine Region, 1 foot elsewhere.
    Applies: New or substantially improved structures, including homes, in special flood hazard areas; the lowest floor includes the basement.
    § 82-28.1002 · code text
    New construction and substantial improvement of any structure shall have the lowest floor, including basement, elevated to or above the base flood elevation plus required freeboard.
  • Above highest adjacent grade by at least the FIRM depth number plus freeboard, or at least 2 feet if none.
    Applies: New or substantially improved structures, including homes, in zones AH, AO or VO.
    § 82-28.1002 · code text
    New construction and substantial improvement of any structure in zone AH, AO or VO shall have the lowest floor, including basement, elevated above the highest adjacent grade at least as high as the depth number specified in meters (feet) on the FIRM plus required freeboard, or at least 0.61 meters (two feet) if no depth number is specified.

Who this affects

HomeownersContractorsDesigners

Frequently asked questions

What are the rules for building in a Contra Costa County flood zone?

Contra Costa County's code: A county public works floodplain permit is needed before construction, a grading or building permit, or any development. (Property in any special flood hazard area.) (§ 82-28.802); At or above base flood elevation plus 2 feet in the San Francisco Bay Delta Estuarine Region, 1 foot elsewhere. (New or substantially improved structures, including homes, in special flood hazard areas; the lowest floor includes the basement.) (§ 82-28.1002).

General information, not legal advice.

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