Trees are beautiful. They provide shade, they suck up groundwater to prevent basement flooding, they look pretty, and their roots hold hills together. They do provide a lot of benefits.
They also cause problems when they are too close to buildings. Their roots ruin foundations, the leaves clog gutters and sewers, their acidity ruins roofs, and they cause damage or injury when branches fall. For this reason, it is best to keep trees away from buildings and high use areas and to prune any nearby trees before they become problematic.
In many cities, you are not allowed to just cut down a tree or even prune it. There’s often rules about where trees are allowed to be cut down, how many are allowed to be cut down, and what size trees are allowed to be cut down. Many land use codes refer to large trees as “exceptional,” “significant,” or “protected.” These are trees that have strict limitations for removal due to their size. The size is commonly measured by the diameter of the trunk at “breast height,” which is 4.5’ above the ground. Different species have different thresholds of trunk diameter that cause them to be considered exceptional. Typically, if a tree is considered exceptional (or whatever special term your city uses), you simply cannot cut it down, AND you can’t even build or disturb the soil within a certain distance of it.
If a tree is classified as exceptional, most cities will require you to hire an arborist to document the species and size of the tree, and that arborist will be required to write a report to describe how it must be protected during construction with fences, excavation methods, and other techniques. Additionally, their report also prescribes the “dripline” which is the outer ring of its canopy. Generally, the roots stretch out as far as the branches, so the dripline distinguishes the land that often cannot be disturbed. In some cities, the dripline is divided into an “inner root zone” and an “outer root zone.” The inner root zone is an area that absolutely cannot be disturbed, and an outer root zone is an area that might be allowed to have certain minimal disturbance with special monitoring and expert oversight from a certified arborist.
This really puts a burden on construction since additional setbacks from exceptional trees paired with other limitations like setbacks from property lines, setbacks from steep slopes, limitations to the percentage of land allowed to be developed, and other limiting factors really makes it a challenge to build. With so many factors limiting development, land gets harder and harder to build on, it becomes less valuable while causing other available land to become increasingly more expensive, and consequently less housing gets built which contributes to the ongoing housing shortage and overpriced homes.
As a homeowner with trees on your property, you really need to be diligent about this. If a tree is getting larger and larger each year, at some point it might be considered “exceptional,” and you won’t be allowed to remove it even though it will literally start to destroy your home (and maybe even you). It is best to remove these beasts before they become a problem. Small problems are easier to solve than big ones (cheaper to remove smaller trees too). As a tree gets bigger and bigger, at some point cutting it down would cause it to fall on your home, and that causes tree crews to expensively dismantle it limb by limb to avoid costly damage. It would have been much cheaper to remove that tree when it was a little twig. Or better yet, it would have been best to just plant it far from your home in the first place.
In Seattle, there is new legislation that categorizes all trees into tier 1-4. Tier 1 trees have historic historic significance and cannot be altered. Tier 2 trees are any with trunks 24” in diameter or greater (and additional smaller trees on a special list). Tier 3 trees have trunks 12” to 24” that aren’t on the special list from Tier 2. Tier 4 includes all trees with trunks 6” to 12” that are not on the special list. When removing or pruning trees that are Tier 1-4, there are special reporting requirements and permit fees depending on the situation. More detail is provided at https://www.seattle.gov/DPD/Publications/CAM/Tip242B.pdf
The moral of the story is to remove your potentially problematic trees before their trunks become 6”, or you will have a hard time (and expensive time) dealing with them once they have matured. The other main point is to be very thoughtful about where you plant trees. Remember that they grow up to become monsters that will damage your property if planted too close to your home.
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