AVOIDING TREE DAMAGE DURING CONSTRUCTION

    As cities and suburbs expand, wooded lands are being developed
    into commercial and residential sites. Homes are constructed in the
    midst of trees to take advantage of the aesthetic and environmental
    value of the wooded lots. Wooded properties can be worth as much
    as 20 percent more than those without trees, and people value the
    opportunity to live among trees.
    Unfortunately, the processes involved with construction can be
    deadly to nearby trees. Unless the damage is extreme, the trees
    may not die immediately but could decline over several years. With
    this delay in symptom development, you may not associate the loss
    of the tree with the construction.

    It is possible to preserve trees on building sites if the right measures
    are taken. The most important step is to hire a professional arborist
    during the planning stage. An arborist can help you decide which
    trees can be saved and can work with the builder to protect the
    trees throughout each construction phase.
    How Trees Are Damaged During Construction
    Physical Injury to Trunk and Crown. Construction equipment can injure
    the aboveground portion of a tree by breaking branches, tearing the bark,
    and wounding the trunk. These injuries are permanent and, if extensive, can
    be fatal.
    Cutting of Roots. The digging and trenching that are necessary to
    construct a house and install underground utilities will likely sever a portion
    of the roots of many trees in the area. It is easy to appreciate the potential
    for damage if you understand where roots grow. The roots of a tree are
    found mostly in the upper 6 to 12 inches of the soil. In a mature tree, the
    roots extend far from the trunk. In fact, roots typically are found growing a
    distance of one to three times the height of the tree. The amount of damage
    a tree can suffer from root loss depends, in part, on how close to the tree
    the cut is made. Severing one major root can cause the loss of 5 to 20
    percent of the root system.
    Another problem that may result from root loss caused by digging and
    trenching is that the potential for the trees to fall over is increased. The
    roots play a critical role in anchoring a tree. If the major support roots are
    cut on one side of a tree, the tree may fall or blow over.
    Less damage is done to tree roots if utilities are tunneled under a tree rather
    than across the roots.
    Soil Compaction. An ideal soil for root growth and development is about
    50 percent pore space. These pores—the spaces between soil
    particles—are filled with water and air. The heavy equipment used in
    construction com-pacts the soil and can dramatically reduce the amount of
    pore space. This compaction not only inhibits root growth and penetration
    but also decreases oxygen in the soil that is essential to the growth and
    function of the roots.
    Smothering Roots by Adding Soil. Most people are surprised to learn
    that 90 percent of the fine roots that absorb water and minerals are in the
    upper 6 to 12 inches of soil. Roots require space, air, and water. Roots
    grow best where these requirements are met, which is usually near the soil
    surface. Piling soil over the root system or increasing the grade smothers
    the roots. It takes only a few inches of added soil to kill a sensitive mature
    tree.
    Exposure to the Elements. Trees in a forest grow as a community,
    protecting each other from the elements. The trees grow tall, with long,
    straight trunks and high canopies. Removing neighboring trees or opening
    the shared canopies of trees during construction exposes the remaining
    trees to sunlight and wind. The higher levels of sunlight may cause
    sunscald on the trunks and branches. Also, the remaining trees are more
    prone to breaking from wind or ice loading.
    Getting Advice
    Hire a professional arborist in the early planning stage. Many of the trees on
    your property may be saved if the proper steps are taken. Allow the arborist
    to meet with you and your building contractor. Your Tree Works arborist can
    assess the trees on your property, determine which are healthy and
    structurally sound, and suggest measures to preserve and protect them.
    One of the first decisions is determining which trees are to be preserved
    and which should be removed. You must consider the species, size,
    maturity, location, and condition of each tree. The largest, most mature
    trees are not always the best choices to preserve. Younger, more vigorous
    trees usually can survive and adapt to the stresses of construction better.
    Try to maintain diversity of species and ages. We can advise you about
    which trees are more sensitive to compaction, grade changes, and root
    damage.
    Planning
    Treeworks and your builder should work together in planning the
    construction. The builder may need to be educated regarding the value of
    the trees on your property and the importance of saving them. Few builders
    are aware of the way trees’ roots grow and what must be done to protect
    them.
    Sometimes small changes in the placement or design of your house can
    make a great difference in whether a critical tree will survive. An alternative
    plan may be more friendly to the root system. For example, bridging over
    the roots may substitute for a conventional walkway. Because trenching
    near a tree for utility installation can be damaging, tunneling under the root
    system may be a good option.
    Erecting Barriers
    Because our ability to repair construction damage to trees is limited, it is
    vital that trees be protected from injury. The single most important action
    you can take is to set up construction fences around all of the trees that are
    to remain. The fences should be placed as far out from the trunks of the
    trees as possible. As a general guideline, allow 1 foot of space from the
    trunk for each inch of trunk diameter. The intent is not merely to protect the
    aboveground portions of the trees but also the root systems. Remember
    that the root systems extend much farther than the drip lines of the trees.
    Instruct construction personnel to keep the fenced area clear of building
    materials, waste, and excess soil. No digging, trenching, or other soil
    disturbance should be allowed in the fenced area.
    Protective fences should be erected as far out from the trunks as possible
    in order to protect the root system.
    Limiting Access
    If at all possible, it is best to allow only one access route on and off the
    property. All contractors must be instructed where they are permitted to
    drive and park their vehicles. Often this same access drive can later serve
    as the route for utility wires, water lines, or the driveway.
    Specify storage areas for equipment, soil, and construction materials. Limit
    areas for burning (if permitted), cement wash-out pits, and construction work
    zones. These areas should be away from protected trees.
    Specifications
    Get it in writing. All of the measures intended to protect your trees must be
    written into the construction specifications. The written specifications
    should detail exactly what can and cannot be done to and around the trees.
    Each subcontractor must be made aware of the barriers, limitations, and
    specified work zones. It is a good idea to post signs as a reminder.
    Fines and penalties for violations should be built into the specifications. Not
    too surprisingly, subcontractors are much more likely to adhere to the tree
    preservation clauses if their profit is at stake. The severity of the fines
    should be proportional to the potential damage to the trees and should
    increase for multiple infractions.
    Maintaining Good Communications
    It is important to work together as a team. You may share clear objectives
    with your arborist and your builder, but one subcontractor can destroy your
    prudent efforts. Construction damage to trees is often irreversible.
    Visit the site at least once a day if possible. Your vigilance will pay off as
    workers learn to take your wishes seriously. Take photos at every stage of
    construction. If any infraction of the specifications does occur, it will be
    important to prove liability.
    Final Stages
    It is not unusual to go to great lengths to preserve trees during construction,
    only to have them injured during landscaping. Installing irrigation systems
    and rototilling planting beds are two ways the root systems of trees can be
    damaged. Remember also that small increases in grade (as little as 2 to 6
    inches) that place additional soil over the roots can be devastating to your
    trees. Careful planning and communicating with landscape designers and
    contractors is just as important as avoiding tree damage during
    construction.
    Post-Construction Tree Maintenance
    Your trees will require several years to adjust to the injury and
    environmental changes that occur during construction. Stressed trees are
    more prone to health problems such as disease and insect infestations.
    Talk to us about continued maintenance for your trees. Continue to monitor
    your trees, and have them periodically evaluated for declining health or
    safety hazards.
    Despite the best intentions and most stringent tree preservation measures,
    your trees still might be injured from the construction process. Tree Works
    can suggest remedial treatments to help reduce stress and improve the
    growing conditions around your trees.