Seattle, WA Environmental Rules: Flood Elevation Requirements (2026)
Key Facts
- Freeboard required
- 3 feet above base flood elevation (A zones)
- VE zone standard
- Elevation at base flood elevation itself
- Vertical datum
- NAVD 88 mean sea level reference
- Governing sections
- SMC 25.06.030 and 25.06.110
- Enforcing department
- Seattle Department of Construction and Inspections
Summary
Seattle requires new construction in A-zone flood hazard areas to sit at least three feet above the base flood elevation, per SMC 25.06.030's definition of 'flood protection elevation.' SMC 25.06.110 applies the standard to residential and nonresidential buildings citywide, enforced by the Seattle Department of Construction and Inspections.
"Base flood elevation (BFE)" or "base flood level" means the level or elevation above mean sea level, as calculated by reference to the vertical datum of NAVD 88, to which floodwater is anticipated to rise during the base flood. ... "Flood protection elevation" means the following unless otherwise permitted by code:1.Base flood elevation in the VE zone; and2.For A zones:a.Three feet above the base flood elevation for new construction except for floating structures;b.Base flood elevation for floating structures;c.For substantial improvement except for floating structures, if the elevation of the existing structure is:1)At or above base flood elevation, the elevation of the existing structure; or2)Below base flood elevation, base flood elevation plus three feet.
Official source re-checked September 7, 2026: no newer edition of the code had been published (publisher’s edition: Municipal Code: Supplement 44 Update 1).
Full Breakdown
030 defines 'base flood elevation (BFE)' as the level above mean sea level, calculated by reference to the NAVD 88 vertical datum, to which floodwater is anticipated to rise during the base flood, the flood with a one percent annual chance of being equaled or exceeded. The same section then defines 'flood protection elevation,' the actual construction standard: in a VE zone, it equals the base flood elevation; in an A zone, new construction (other than floating structures) must reach three feet above BFE, floating structures need only reach BFE itself, and substantially improved existing structures use their current elevation if it's already at or above BFE, or BFE plus three feet if it isn't.
A applies this to residential construction, requiring the lowest floor, including any basement, at or above the flood protection elevation in AE and other A zones where BFE is known. C. C must sit at or above the flood protection elevation, or the 500-year flood height where available, because even a slight flood risk is considered unacceptable for those uses.
Violations & Fines
Building with the lowest floor below the required flood protection elevation, or dry-floodproofing a nonresidential structure without the required engineer or architect certification, violates SMC 25.06.110. SMC 25.06.140 backs the standard with a cumulative civil penalty of $500 per day, running from the date the violation began until compliance is achieved, in addition to any other enforcement action the City may take.
Frequently Asked Questions
How much freeboard does Seattle require above base flood elevation?
Does the freeboard rule apply to commercial buildings too?
What vertical reference does Seattle use to measure base flood elevation?
Sources & Official References
Other rules in Seattle
Compare Seattle to another location·View the Washington environmental rules overview
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Flood Elevation Requirements in Nearby Cities
How other cities in King County handle flood elevation requirements.