Mirrormont Landscaping Rules: Tree Removal & Heritage Trees Rules (2026)

King County regulates tree removal primarily through KCC Title 16.82 (Clearing and Grading) and Title 21A.24 (Critical Areas). On a typical residential parcel outside critical areas, removing a few yard trees for safety or landscaping generally does not require a county permit, though removing more than 7,000 square feet of vegetation on steep slopes, over 5,000 cubic yards of earth, or significant trees within any designated critical area or its buffer triggers permit review. Significant trees are typically defined as 6 inches or larger diameter at breast height (some zones use 12 inches). In critical areas such as wetlands, fish and wildlife habitat conservation areas (notably salmon-bearing streams), shorelines, erosion hazard areas, and steep slopes, tree removal is restricted to preserve stormwater retention, habitat, and slope stability. The Washington DNR administers the Forest Practices Act (RCW 76.09) for commercial timber harvests on parcels generally over 20 acres; a Forest Practices Application is required before cutting. Hazard trees that pose imminent risk may be removed under an emergency exemption with photo documentation and replanting required. Replanting ratios of 3:1 or more are common for permitted removals in buffers.