Thurston County, WA Fence Regulations: Retaining Walls (2026)

Section 14.17.030 amends International Building Code [A]105.2, the work-exempt-from-permit list Thurston County enforces, and item 4 sets the retaining-wall threshold: a wall that is "not over four feet (1,219 mm) in height measured from the bottom of the footing to the top of the wall" needs no building permit, unless it supports a surcharge or impounds Class I, II, or IIIA liquids, in which case the exemption disappears no matter how short the wall is.

A retaining wall that exceeds four feet, or that carries a surcharge load or hazardous liquids at any height, falls under the general permit rule in § 14.17.030's [A]105.1: the owner or an authorized agent must apply to the Thurston County Community Planning and Economic Development Department and obtain a permit before construction starts. Fees follow the schedule set under § 14.17.050, based on the department's valuation of the work, and the permit expires one year after issuance unless an inspection is approved or an extension is granted for justifiable cause.

The exemption from a permit is not an exemption from the rest of the code: § 14.17.030's own text warns that work exempt from a permit can still require review under other chapters, including Chapters 14.37 and 14.38, or Titles 15 through 25, so a retaining wall tied to grading, stormwater, or critical-areas work can trigger separate approvals even at four feet or under. Build a wall over four feet without the required permit and § 14.17.060 treats it as a class 1 civil infraction under Chapter 7.80 RCW, with the code's misdemeanor backstop under [A]114.5 adding a fine of up to $1,000, up to ninety days in jail, or both.