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Building in a flood zone in Millbrae

Millbrae'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 Millbrae Municipal Code it was read from, with the code text one click away (checked October 2026). General information, not legal advice.

What Millbrae's code says

Millbrae code What Millbrae's code adds
Floodplain permit
  • A development permit is needed before construction or development begins in any special flood hazard area.
    Covers construction, fill, storage of materials, drainage facilities, and changing or moving a watercourse.
    § 8.50.100 · code text
    A development permit shall be obtained before construction or other development begins within any area of special flood hazard established in MMC § 8.50.040.
Building in a floodway
  • All encroachments, including fill and new construction, are banned unless a registered engineer certifies no base flood level rise.
    Applies: Applies in designated floodways. Allowed development must also meet the flood hazard reduction rules.
    § 8.50.190 · code text
    All encroachments are prohibited, including fill, new construction, substantial improvements and other development unless certification by a registered professional engineer is provided demonstrating that encroachments shall not result in any increase in the base flood levels during the occurrence of the base flood discharge;
Height of the lowest floor
  • Lowest floor at least the flood map depth number plus 1 foot above highest adjacent grade; 2 feet if none.
    Applies: New or substantially improved homes in an AO zone.
    § 8.50.140 · code text
    In an AO zone, elevated above the highest adjacent grade to a height equal to or exceeding one foot above the depth number specified in feet on the FIRM, or elevated at least two feet above the highest adjacent grade if no depth number is specified;
  • The lowest floor must be at least 2 feet above the base flood elevation.
    Applies: New or substantially improved homes in an A zone.
    § 8.50.140 · code text
    In an A zone, elevated to or above the base flood elevation by at least two feet; said base flood elevation shall be determined by one of the methods in MMC § 8.50.120;
  • The lowest floor must be at least 2 feet above the base flood elevation.
    Applies: New or substantially improved homes in flood zones other than AO and A.
    § 8.50.140 · code text
    In all other zones, elevated to or above the base flood elevation by at least two feet.

Who this affects

HomeownersContractorsDesigners

Frequently asked questions

What are the rules for building in a Millbrae flood zone?

Millbrae's code: A development permit is needed before construction or development begins in any special flood hazard area. (Covers construction, fill, storage of materials, drainage facilities, and changing or moving a watercourse.) (§ 8.50.100); Lowest floor at least the flood map depth number plus 1 foot above highest adjacent grade; 2 feet if none. (New or substantially improved homes in an AO zone.) (§ 8.50.140).

General information, not legal advice.

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Millbrae Municipal Code — full text