In the Pacific Northwest we are fortunate to be surrounded by trees. However, it can be tricky to navigate jurisdictional requirements when planned residential construction is affected by existing trees. In this article we will explain the general requirements around tree classification, removal and protection in the Greater Seattle Area. As every city is different, you should always check with your local building department.
TREE CATEGORIZATIONS
Requirements around tree removal vary based on tree size and location. First, it is helpful to know the size of your tree(s) and how they may be classified. To determine the size of an existing tree, find its diameter by measuring the circumference of the trunk at 4'-6" above the ground and dividing that number by 3.14. This is the tree’s diameter. The following terms are often used to classify different trees.
Protected Trees – Trees of exceptional size or rarity, historic significance or a landmark in the community. Cities might refer to these trees with different terms such as “Historic” or “Heritage”. Generally, these trees can only be removed when they pose a safety concern to people or property.
Landmark Trees – Large trees with a diameter greater than 24”/30", depending on the jurisdiction. Removing these trees will require approval and replacement with one or more new trees.
Significant Trees – These trees have a diameter greater than 6" but less than 24”/30". Often a limited number of these trees can be removed each year with some regulations.
Critical Areas Trees – this includes trees designated as part of a preservation plan or those existing in protected areas, easements, wetlands, or buffer zones. Removal of these trees will only be allowed when meeting certain requirements and will require replacement.
TREE REMOVAL REQUIREMENTS
Building departments consider many variables around tree removal. Aside from the natural beauty of trees in our residential areas, maintaining a robust tree canopy promotes healthy air, maintains animal habitats, reduces energy use when shading homes, reduces soil erosion, and is proven to improve mental health. Therefore, jurisdictions in the Seattle area have various requirements that include combinations of arborist input, permits, and tree replacement.
Unrestricted Removal - Trees with a diameter under 6" are usually easiest to remove. You should always check with your local building department, but many cities have no restriction on the number of small trees that can be removed per year and do not require permits or replacement.
Limited Removal - Significant trees (generally 6"-24”/30" diameter) can often be removed, usually with a limit on the number per year based on lot size. Some areas also require a permit for removal and/or replacement trees to be planted.
Restricted Removal - Landmark trees and/or protected trees generally require a certified arborist report, removal permit, and replacement with more than one tree. They may not be approved for removal.
Emergency Removal - most jurisdictions have exceptions for trees that are diseased or present an imminent threat to people or property and will issue a retroactive permit. However, it is important to document the disease and/or threat posed by the tree.
Generally, a site plan is required when applying for a permit to show which trees are being removed. Below is an example site plan created as part of a property survey. A survey may not be required and there are many ways to obtain a site plan for tree removal. In most municipalities, there are heavy fines for removing trees without approval. Always check with your local building department before having trees removed.
TREE PRESERVATION REQUIREMENTS
Trees being preserved during a construction project are required to be surrounded with fencing and proper signage. Most cities provide a diagram to show where and what kind of fencing is required (at the dripline, or a set number of feet beyond the dripline), what signage is needed, and any additional requirements. No soil disturbance or storage of materials is allowed within the fenced area. The diagrams below outline these slightly different requirements in the cities of Seattle and Redmond.
As architects, we are familiar with the tree codes in most cities in the Greater Seattle Area. We can design with these requirements in mind and help our clients navigate the different phases of their projects. Though requirements vary by jurisdiction, we hope these general guidelines clarify how to consider trees and residential construction. To learn more about restrictions in your area, check your local building department’s website. Below are helpful links for the cities we often work with.