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Construction Damage to Trees

Protecting valuable trees from construction damage

By: Sandy Feather ©2014
Penn State Extension


Q. We built our dream house on a wooded lot, and took down as few trees as possible. We love the shade they provide, and enjoy the close-up antics of birds and squirrels. We have been in the house for a little over two years, and are concerned about some of the trees. Some of them have quite a few dead branches and do not seem to be doing very well. What can we do to help them?

A. It would be helpful to know the species of trees on your lot, since there are problems such as the accidentally-introduced emerald ash borer (EAB) that has been killing ash trees in the Pittsburgh area since before 2007. However, it is likely that some of your trees are suffering from construction damage; this is a common problem when construction occurs near mature trees.


Construction injures established trees in a number of ways:

Heavy equipment running over the roots of trees often damages the roots and compacts the soil around them.

Trenching for utility lines, sidewalks and driveways, and digging out for the foundation can remove or damage significant portions of the trees’ root systems.

Changing the grade of the soil around the trees also takes its toll. Some species of trees such as oaks are very sensitive to having additional soil placed over their root systems. Even as little as two inches of additional soil can cause life-threatening problems for them.

Soil fill over tree roots

Obvious mechanical damage to the trees can also be a problem, especially if it involves a large portion of the trunk (trees can recover from small injuries).

Finally, construction often radically alters the overall environment including water drainage patterns, available light, new patterns of pedestrian and vehicular traffic, and the use of deicing salts where they were not used prior to construction.

Established trees often cannot adapt to such abrupt changes in their environment. The stress also makes them more susceptible to disease and insect problems.

You may be surprised to learn that a tree’s root system can extend out from the trunk one to three times the height of the tree. The fine feeder roots, those responsible for absorbing water and nutrients, are primarily found in the upper six to eighteen inches of soil. Consequently, a tree’s root system can be severely damaged even if equipment has not been working directly under its branches.

Dieback in treetops

It is a good idea to contract with a certified arborist before construction begins. A certified arborist can help identify which trees are worth keeping and which ones should be removed. They also can work with the contractor to set up protection zones around the trees you want to keep. These protection zones are designed to keep heavy equipment away from the trees’ root systems, prevent additional soil from being placed over their root systems, and to protect trees from mechanical damage.

 

Is the Damage Done?

Now that the damage has been done, you would still be wise to hire a certified arborist to determine if there is anything that can be done to save your declining trees. If the trees are not too far-gone, removing dead or dying branches, mulching, fertilizing and cleaning up mechanical damage to the bark can prolong their lives.

Many arborists also use air spades to remove excess soil from over trees’ root systems without causing additional damage to the roots as would happen with other types of digging equipment. Arborists are certified through the International Society of Arboriculture (ISA).

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