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Mill Valley · Building on your lot

Building in a flood zone in Mill Valley

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

What Mill Valley's code says

Mill Valley code What Mill Valley's code adds
Floodplain permit
  • A development permit is needed before any construction or development, including manufactured homes, in a special flood hazard area.
    § 18.04.090 · code text
    a development permit meeting the requirements of this chapter shall be obtained before any construction or other development, including manufactured homes, within any special flood hazard area established by Section 18.04.050(B).
Building in a floodway
  • No encroachments, including fill, unless a registered engineer or architect shows no rise in flood elevation.
    Applies: Applies in an adopted regulatory floodway, for flood elevation during the base flood discharge.
    § 18.04.110 · code text
    No encroachments, including fill, or other development, as defined by this chapter, shall be permitted within an adopted regulatory floodway, unless it is demonstrated by a registered professional engineer or architect that the encroachment shall not result in an increase in flood elevation during the occurrence of the base flood discharge.
Height of the lowest floor
  • The lowest floor must be 1 foot above the base flood elevation.
    Applies: New or substantially improved homes in AE and AH zones.
    § 18.04.100 · code text
    Elevated one foot above the base flood elevation in AE and AH zones;
  • 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 AO zones. Measured from the building pad's highest adjacent grade.
    § 18.04.100 · code text
    Elevated above the highest adjacent grade of the building pad 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 in AO zones.

Who this affects

HomeownersContractorsDesigners

Frequently asked questions

What are the rules for building in a Mill Valley flood zone?

Mill Valley's code: A development permit is needed before any construction or development, including manufactured homes, in a special flood hazard area. (§ 18.04.090); The lowest floor must be 1 foot above the base flood elevation. (New or substantially improved homes in AE and AH zones.) (§ 18.04.100).

General information, not legal advice.

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Ask GoCodebook how Mill Valley's building in a flood zone rules apply to your situation and get an answer that cites the section.

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