King County, WA Fence Regulations: Retaining Walls (2026)
Key Facts
- Permit-exempt height
- 4 feet, footing to top
- Exemption voided by
- surcharge or hazardous-liquid impoundment
- Governing code
- K.C.C. 16.02.240, IBC § 105.2 substitute
- Permitting office
- DLS Permitting Division
- Applies in
- unincorporated King County only
Summary
Unincorporated King County requires a building permit for any retaining wall over 4 feet tall, or any wall of any height that holds back a surcharge or stores hazardous liquids.
Work exempt from permit (IBC 105.2). A building permit shall not be required for the following: ... 4. Retaining walls that are not over 4 feet (1.2 m) in height measured from the bottom of the footing to the top of the wall, unless supporting a surcharge or impounding Class I, II or IIIA liquids.
Full Breakdown
King County Code § 16.02.240 exempts retaining walls from a building permit only when they are 4 feet or less, measured from the bottom of the footing to the top of the wall, and are not holding back a surcharge load or impounding Class I, II or IIIA liquids. Cross a 4-foot footing-to-top measurement, or add a surcharge behind the wall, and the exemption disappears: you need a building permit through the Department of Local Services, Permitting Division, with engineered plans. This rule applies only in unincorporated King County; Seattle, Bellevue, Kent, Renton, Federal Way and the county's other 25-plus incorporated cities enforce their own building codes.
Violations & Fines
Building without a required permit exposes the owner to stop-work orders and permit-related penalties under K.C.C. Title 23, plus the cost of after-the-fact engineering and permitting to legalize the wall.
Frequently Asked Questions
Do I need a permit for a 3-foot retaining wall in unincorporated King County?
Does this cover a retaining wall in Seattle or Bellevue?
Sources & Official References
Other rules in King County
Compare King County to another location·View the Washington fence regulations overview
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