What Is a Significant Tree? (Tree Permit Rules by City)

A significant tree is a tree that is legally protected by city code once it reaches a certain diameter at breast height (DBH).
When a tree crosses that threshold, permits, arborist reports, and mitigation are often required before removal or major pruning.

These size thresholds are different in every city — what’s legal in Puyallup may be illegal in Bellevue or Renton.

Significant Tree Size by City (DBH)

“DBH” means diameter measured at 4.5 ft above grade. Rules vary by city and site conditions (especially ECAs).

City Significant Tree Size Notes
Bellevue 6" DBH+ Applies to viable trees under Bellevue land-use code.
Federal Way 6" DBH+ Removal of trees ≥ 6" DBH generally requires city approval.
Issaquah 6" DBH+ Standard threshold used for regulated trees in most zones.
Kent 6" DBH+ Common permit and retention trigger size.
Newcastle 6" DBH+ Standard significant-tree size for removal permitting.
Puyallup 15" DBH+ Notably higher threshold than most nearby cities.
Renton 6" DBH+ Exception: alder and cottonwood typically qualify at 8" DBH+.
Sammamish 6" DBH+ Standard municipal significant-tree threshold.
Seattle 6" DSH / DBH+ Threshold varies by lot, tree type, and removal window.
Shoreline 6" DBH+ Common regulated-tree size under local code.
Tacoma 6" DBH+ Applies to most regulated trees; some zones differ.

Tip: If you’re close to the threshold (or in a steep slope / wetland / shoreline buffer), assume permitting may apply. Use our Tree Diameter Calculator.

Why 6 inches is the standard across most cities

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Most cities in Washington regulate trees starting at 6 inches DBH because that size aligns with professional arborist standards used nationwide.


Under ISA (International Society of Arboriculture) and ANSI A300 guidelines, trees at or above 6" DBH are considered established structural trees — large enough to provide meaningful canopy, stormwater control, and habitat, and large enough that improper removal can cause environmental harm.


Cities adopted this threshold into municipal codes so that trees are reviewed before they reach sizes that would cause erosion, slope failure, or canopy loss if removed without oversight.

What Happens If Your Tree Is “Significant”?

Once a tree meets your city’s “significant tree” threshold, removal and major pruning are often regulated under municipal code. The exact rules vary, but most cities require documentation before approval is granted.

Common requirements

  • 🧾 City review or permit approval
  • 📋 Site plan or tree inventory (when required)
  • 🌲 Arborist report for condition, impacts, or justification
  • ⚠️ Tree risk assessment for hazard-related removals
  • 🌱 Mitigation or replanting requirements

Why cities regulate them

  • Canopy retention and neighborhood tree cover
  • Slope stability and erosion control
  • Stormwater and drainage impacts
  • Wildlife habitat and ecological function
  • Protection of ECAs (steep slopes, wetlands, shorelines)

How to Measure Tree Diameter (DBH)

Cities measure tree size using Diameter at Breast Height (DBH). This is the standard method used by arborists, cities, and permit departments.

1. Find breast height

Measure 4.5 feet above ground on the uphill side of the tree. This height is fixed in nearly all city codes.

2. Measure the trunk

Wrap a tape measure around the trunk at 4.5 ft to get the circumference. Divide by 3.1416 (π) to get diameter, or use a diameter tape.

3. Special cases

For multi-stem trees, leaning trees, or trees on slopes, cities use special measurement rules — this is where arborist verification matters.

Use our free tool: Tree Diameter Calculator to convert circumference to DBH and see if your tree may be regulated.

Can a Significant Tree Be Removed?

In most cities, the answer is yes — but removal typically requires documentation and, in many cases, permit approval. Even when a tree is hazardous, cities usually want a clear record showing why removal is justified.

Common reasons cities approve removal

  • ⚠️ Verified hazard / failure potential
  • 🪲 Significant decline, disease, or pest impacts
  • 🏠 Documented conflict with structures or required clearances
  • 🧱 Development or construction with approved plans
  • 🌧️ Site stability concerns (steep slopes, erosion, drainage)

What’s usually needed

  • 📋 Tree species + DBH measurement (and location)
  • 🌲 Arborist report describing condition and impacts
  • 🧭 Site context (slope, soil, proximity to targets)
  • 🧾 Permit application / city review (when required)
  • 🌱 Mitigation or replanting plan (often required)

Important: If your tree is in a critical area (ECA) such as a steep slope, wetland, stream buffer, or shoreline, additional review may apply even when the tree meets removal criteria.

Helpful next steps: Tree Removal Permits by City · Arborist Reports & Permit Documentation · Tree Risk Assessments (TRAQ)

Significant Tree & Permit FAQs

These are the most common questions homeowners ask when they’re trying to determine whether a tree is regulated, whether a permit is required, and what happens if a significant tree needs to be removed. While rules vary by city and site conditions, these answers reflect how significant tree codes are typically enforced across the Puget Sound region.

  • What is considered a “significant tree”?

    A significant tree is a tree that becomes legally protected once it reaches a minimum diameter at breast height (DBH) set by city code. In most Puget Sound cities, this threshold is 6 inches DBH, meaning permits or city approval are required before removal or major pruning.

  • How big does a tree have to be to be considered significant?

    In most Washington cities, a tree becomes significant at 6 inches in diameter, measured 4.5 feet above the ground (DBH). Some cities use higher thresholds (such as 15 inches in Puyallup) or apply stricter rules inside steep slopes, wetlands, and shoreline buffers.

  • Do I need a permit to remove a significant tree?

    Yes. Once a tree meets the city’s significant-tree size threshold, removal, topping, or heavy pruning typically requires a permit or city review. Many cities also require an arborist report, tree inventory, or mitigation plan before approval is granted.

  • Can a significant tree be removed if it is dangerous?

    Yes — but cities require documentation showing the risk. This is usually done with an ISA Tree Risk Assessment (TRAQ) or an arborist report that verifies decay, structural defects, root failure, or likelihood of impact to people or property.

  • How do I know if my tree meets the size threshold?

    Measure the trunk at 4.5 feet above the ground on the uphill side of the tree. If the tree is multi-stemmed or on a slope, special measurement rules apply. You can calculate DBH from circumference using a tree diameter calculator or have an arborist verify it.

  • What happens if I remove a significant tree without a permit?

    Cities can issue stop-work orders, fines, replacement requirements, civil penalties, and property liens. In some jurisdictions, illegal removal can cost tens of thousands of dollars in mitigation and restoration fees.

  • Do Environmentally Critical Areas (ECAs) change the rules?

    Yes. If a tree is located in a steep slope, wetland, stream buffer, or shoreline, even small trees may be protected. ECAs often trigger stricter review, arborist reports, and geotechnical oversight, even when the tree meets normal removal thresholds.

🌲Need Help with a Regulated or Significant Tree?


Whether you’re dealing with a significant tree, an ECA (critical area), or a city permit requirement, Sound Tree Care helps homeowners move forward safely, legally, and without guesswork.

Our ISA-Certified Arborists specialize in documenting hazardous trees, navigating city tree codes, and preparing permit-ready reports for regulated properties across the Puget Sound region.


We provide code-compliant solutions for:

  • Significant tree removals
  • Steep slopes, wetlands, and shoreline buffers
  • Permit-required tree work
  • Development and construction impacts
  • Hazard and risk-based removals


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