Thurston County, WA Environmental Rules: Flood Elevation Requirements (2026)
Key Facts
- Freeboard
- 2 feet above base flood elevation, all buildings
- Residential elevation floor
- Lowest floor above freeboard or highest recorded flood
- Manufactured homes
- Lowest floor 2 feet above BFE, anchored
- Maximum penalty
- $1,000 fine and/or 90 days jail per day
- Permit required
- Before any construction in mapped flood hazard area
Summary
Thurston County requires two feet of freeboard above the base flood elevation for new construction and substantial improvements in special flood hazard areas. TCC § 14.38.050(B)(1)(a) sets the elevation floor for residential structures, while § 14.38.020 extends the same two-foot freeboard standard to non-residential buildings, floodproofed commercial buildings, and utility equipment.
"Freeboard" is an increment of elevation added to the base flood elevation. Thurston County defines "freeboard" as two feet of elevation added to the base flood elevation. Freeboard is required for all residential, non-residential, commercial floodproofed buildings, and utilities (all equipment, electrical, or mechanical items) constructed, substantially improved and/or reconstructed due to substantial damage within the special flood hazard area. ... New construction and substantial improvement of any residential structure shall have the lowest floor, including basement, elevated to above the required freeboard (add two feet to the base flood elevation), or the highest known recorded flood elevation, whichever is greater.
Official source re-checked September 7, 2026: no newer edition of the code had been published (publisher’s edition: Code of Ordinances: Supplement 77).
Full Breakdown
020, freeboard means two feet of elevation added to the base flood elevation (BFE), the flood level with a one percent annual chance of occurring, also called the hundred-year flood. Freeboard applies countywide to residential, non-residential and floodproofed commercial buildings, plus all utilities and mechanical, electrical and plumbing equipment, whenever they're constructed, substantially improved, or reconstructed after substantial damage inside a special flood hazard area. 050(B)(1)(a) requires the lowest floor, including any basement, to sit above that two-foot freeboard margin, or above the highest known recorded flood elevation if that number is higher.
050(B)(4), or must be dry floodproofed watertight to that elevation with an engineer's certification of zero rise in flood levels. 050(B)(5). 040(B), and applications must include a current FEMA elevation certificate showing the lowest floor's elevation relative to mean sea level. 060.
Violations & Fines
Building in a special flood hazard area without meeting the freeboard and elevation standards is a misdemeanor under TCC § 14.38.070(A): a fine of up to $1,000, up to 90 days in jail, or both, with every day of continued violation a separate offense. Subsection (C) also declares any violation a public nuisance the county can abate through an injunction in superior court, on top of the criminal penalty.
Frequently Asked Questions
How much freeboard does Thurston County require above the base flood elevation?
Where must the lowest floor of a new house sit in a flood zone?
Does the freeboard rule apply to manufactured homes?
What's the penalty for building below the required flood elevation?
Sources & Official References
Other rules in Thurston County
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