Tree Service in Seattle, Washington

How Seattle’s Tier System Affects Your Tree

Most Seattle tree jobs stall on paperwork, not on the tree. Since the 2023 tree protection ordinance, the city sorts trees into four tiers, and the tier decides whether removal is even on the table. The code was amended again effective January 21, 2026, changing how tree protection areas are calculated and how they interact with buildable area in Neighborhood Residential zones. A lot of the tree-service content online still describes the old rules.

DSH is diameter at standard height. The Tier 2 species list is where homeowners get caught out — a tree well under 24 inches can still be Tier 2 depending on species, with some thresholds as low as 6 inches. We check the list before quoting, not after.

Hazard Removals — What Seattle Actually Requires

For Tier 1 and Tier 2 trees, hazard is effectively the only route to removal outside a development permit. The city does not take your word for it. It asks for an ISA Basic Tree Risk Assessment Form completed by a certified arborist holding a current ISA Tree Risk Assessment Qualification and submitted by a registered tree service provider, an arborist report covering the tree’s health and what it would hit if it failed, and photographs clear enough to identify species and show proximity to structures. Emergencies work differently — you notify SDCI first and a brief narrative replaces the full assessment. Replacement planting is required for hazardous Tier 1, Tier 2 and Tier 3 removals.

Rules change. Confirm your specific tree with Seattle SDCI, or ask us to check it as part of your estimate.

Seattle's Trees & Local Growing Conditions

According to the City of Seattle's own tree guide, the Douglas-fir is the most common tree you'll see across the city — often reaching well over 100 feet on Seattle's hillsides. Alongside it, Western Red Cedar and Bigleaf Maple round out the native canopy that gives neighborhoods like Magnolia, Lakemont, and Wallingford their wooded character.

Each of these species brings its own care needs. Mature Douglas-firs can drop heavy limbs in wind and wet-snow events; Western Red Cedars show stress (thinning, browning tops) during the dry late-summer stretches typical of the Eastside; and fast-growing Bigleaf Maples often need structural pruning to manage weight over homes, driveways, and fences. Seattle's hilly terrain, clay-heavy soils, and proximity to Lake Washington and Lake Sammamish also mean root health and slope stability are real considerations on many removals.

Our certified arborists know how these local species and conditions behave, so we can recommend the right approach — whether that's targeted pruning to preserve a healthy landmark tree or a safe, fully permitted removal.