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

35 CCC, rather than a stand-alone fence or wall chapter. 040 requires a grading permit from the Department of Building and Planning for any grading activity unless a specific exemption applies. 050(P) exempts an excavation below finished grade for basements and footings of a building, retaining wall or other structure authorized by a valid building permit, but the exemption stops at walls with an unsupported height of five feet or less after construction is complete; a taller retaining wall, or any fill placed with the excavated material, falls back under the full grading permit process.

070(H)(5) requires the grading plan's cross-section drawings to show the retaining wall and the adjacent grade for at least 20 feet on either side of the wall, along with maximum depth of cut and fill and existing and proposed building setbacks. 130, triggers a further requirement: the grading plan must be prepared and stamped by a geotechnical engineer, engineering geologist, or civil engineer licensed in Washington. 080(H) separately requires any finished slope steeper than two horizontal to one vertical to be engineered, a standard that reaches many taller retaining walls even when the excavation itself falls under the five-foot permit exemption.