Retaining Walls: Kent vs Seattle
How do retaining walls rules compare between Kent, WA and Seattle, WA?
Kent has fewer restrictions than Seattle.
Kent, WA
King County
Kent requires a building permit for retaining walls over 4 feet tall measured from footing to top. Walls supporting surcharges or on geologically hazardous slopes need a permit at any height under WAC 51-16.
View full Kent rules →Seattle, WA
King County
King County requires a permit for any retaining wall over 4 ft tall or any wall supporting a surcharge load. Walls in landslide or steep-slope critical areas need geotechnical review regardless of height.
View full Seattle rules →Key Facts Comparison
| Fact | Kent | Seattle |
|---|---|---|
| No Permit | Under 4 feet unsurcharged | - |
| Permit Needed | Over 4 feet or surcharge | - |
| Critical Areas | Always permit needed | KCC 21A.24 review |
| Code | WAC 51-16-080 / KCC 11.06 | - |
| Permit Trigger | - | Over 4 ft (footing to top) |
| Surcharge Rule | - | Permit at any height |
| Geotech | - | Required in slope hazards |
| Drainage | - | Required by IRC |
Highlighted rows indicate differences between cities.
Kent FAQ
Do I need a permit for a retaining wall in Kent?
Only if the wall exceeds 4 feet from footing to top, supports a surcharge, or sits in a critical area under KCC 11.06.
Is a rockery considered a retaining wall in Kent?
Yes. Kent treats dry-stack rockeries under the same 4-foot height threshold as engineered retaining walls.
Seattle FAQ
How tall can my retaining wall be without a permit in unincorporated King County?
Up to 4 feet from the bottom of the footing to the top of the wall, with no surcharge load. Walls in a mapped landslide or steep-slope hazard area typically need a permit and geotechnical report regardless of height.
Do I need an engineer for my retaining wall?
Yes if the wall is over 4 feet, supports a surcharge, or is located in a landslide, steep-slope, or erosion hazard area. A licensed geotechnical or civil engineer must prepare the report.
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