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Protect trees during construction project
Dear Ms. Builder: We are planning to make a major several-room addition to our house. We have a beautiful wooded lot and we want to protect the trees. Since there will be some grading, how do we protect the trees? - Mike H.
Dear Mike: When you consider the cost to replace a large tree and reduction in resale value of your house, the death of a tree is a large financial loss. There is also the cost of removing a dead tree. I recently had to pay about $800 to have a large ash tree taken down near my house.
Often the damage done to trees during construction can take four years or more to become apparent. Gradually one tree after another begins to die. Since much of this damage is "invisible" during the construction phase, neither you nor the contractor relates it to the construction done years before.
If your wooded lot is important to you, definitely hire an arborist (tree expert) even before the building plans are complete. The arborist can advise you as to which trees and areas around them that need the most gentle care. For example, this can impact
where a trench is run or where heavy equipment is used and cleaned.
Once your arborist has analyzed your lot, schedule a meeting with your contractor to discuss his report. Also include a clause in the contract to cover any future loss of trees should your contractor not follow the recommendations of your arborist.
Other than a bulldozer smashing into a tree trunk, which is pretty difficult not to notice, the primary indirect damage to trees results from: 1) compacting on the soil, 2) chemicals from construction materials and 3) damage to roots during trenching. Even with no obvious damage, a tree may eventually die from this indirect damage because it is weakened. During a drought or other severe weather, insect infestations, etc., the weakened tree cannot survive as a healthy one would.
As a brief background, good top soil is full of tiny air pockets. Tree roots require these air pockets for oxygen and to provide a holding area for water after a rain. Backing a dump truck or just repeated passes by a pickup truck can compact the soil and destroy these air pockets.
Heavy equipment should avoid any area inside the radius of the drip line of the trees. Your arborist can tell which trees are most sensitive and where your soil is most susceptible to compaction. Mark these areas with some cheap orange plastic fencing available at most home center stores.
Depending on where you live, the soil acidity can range from very acidic to alkaline and various trees prefer various levels of acidity. Many common building material that may end up in the soil, like concrete and brick mortar, are highly alkaline and can affect the soil.
For example, whenever a truck delivers a load of concrete, the chute is hosed down at the end of the job. Mortar mixers are also cleaned out at the end of each work day. Have your arborist discuss this with the contractor to determine a safe location to clean off the equipment with a high alkaline level.
When doing any major room addition, there is going to be some trenching for gas and water lines that may damage roots. Plan the location of these underground lines based on the tree species.
Some trees, like oaks, can handle a substantial amount of root damage (up to 40%). Others, like a beech tree, are much more sensitive to their roots being disturbed.
Here are some sources for arborists and information - American Forests (202) 667-3300, National Arbor Day Foundation (402) 474-5655, World Forestry Center (503) 228-1867, Scenic America (202) 888-4300, International Society of Aboriculture (217) 355-9411.
Send your questions to Ms. Builder, 6906 Royalgreen Dr., Cincinnati, OH 45244 or visit www.dulley.com/msbuilder.