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Tree Protection During Construction

We are used to looking up at trees. But look down at the base of the trunk and imagine roots extending 2x the width of the canopy (or more) all around the tree. The physics of trees are pretty amazing and often misunderstood. For instance, many people don't realize the most sensitive roots are found in the upper 6-12 inches of soil. This makes them easily susceptible to damage. However, they are not visible beneath a lawn or landscaping and thus are easily forgotten.

Construction within a tree's root zone can have severe and lasting impacts. Installing a fence, paving a driveway, building a patio or digging for a drain may cause permanent damage to roots and surrounding soils. Cutting large roots (greater than 2 inches diameter) can negatively impact tree health and stability. Soil compaction by foot traffic, wheeled carts, machinery or heavy materials can also negatively impact tree health or lead to failure in a tree that is already stressed.

The easiest way to protect your trees is consider the root zone in your planning and then install temporary tree protection fencing to prevent damage. A common guideline is to install protective fencing at the "drip line" of the tree (ie. the outer circumference of the canopy). This fencing helps remind everyone to...

  1. Store materials away from the tree

  2. Prevent driving vehicles and heavy equipment over tree roots

  3. Avoid attaching anything to the tree using nails or spikes

  4. A Certified Arborist can help you determine where and how the fence should be installed for maximum benefit. We also recommend adding signage to help everyone understand the purpose of the tree protection zone. Printable Sign - City of Seattle

This reference guide from ISA (International Society of Arboriculture) is a helpful resource.

If you have questions about how to protect trees on your property during a project, contact Tree133.

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