| Damage Control
Protect your trees — and your property value — from construction hazards
By:
Joe Provey
Online Rating:
  (6/10) The beauty of a tree goes far beyond its appearance. Besides being decorative, trees provide privacy, hide unpleasant views, buffer strong winds, reduce erosion, filter the air and lessen your home’s energy consumption. That’s why the premium placed on treed properties can be as much as 20 percent more than those without trees, according to the International Society of Arborculture (ISA).
Nevertheless, homeowners and contractors often fail to consider how home additions and other improvements will affect surrounding trees. For example, excavating for foundations and swimming pools can damage trees dozens of yards away. Even small projects such as tilling a garden bed, laying pipes for lawn irrigation or running an electrical line to a garage or shed can critically injure trees worth thousands of dollars.
The root of the problem
Because a tree’s root system is highly vulnerable, it’s easy to accidentally initiate the demise of a mature, healthy tree without causing any visible damage. In other words, you can’t ensure its survival by simply protecting a tree’s trunk and branches during construction activities.
The root system spreads far beyond the tree’s drip line, to a diameter of one to three times the height of the tree (see illustrations, p. 80). In this area, small, fragile roots work to supply nutrients, oxygen and water to the tree and help to anchor it in an upright position. And though we commonly think of roots as extending deep into the ground, 90 percent of the roots that feed a tree are found within the top 12 to 18 in. of the soil.
To improve a tree’s chances of survival, you must protect its root zone during construction and landscaping projects. The rule of thumb, according to the ISA, is to fence off a root-protection zone with a radius of 1 ft. for every inch of trunk diameter. Within this area, you should avoid trenching, rototilling and regrading, which can cut off significant portions of a tree’s root system.
Raising the grade, compacting the soil, and piling materials, topsoil or debris beneath a tree can also kill the roots. In ideal conditions, about 50 percent of topsoil is filled with pores — tiny open spaces that accommodate moisture and air. Extra weight, including the weight of trucks and heavy equipment, in the root zone can close up these pores and deprive roots of oxygen.
Whether because of ignorance or carelessness, many contractors provide only minimal protection by avoiding obvious damage to tree trunks and branches during construction. It can take several years for a tree to die as a result of root damage, and by then it will be difficult to lay blame.
Contractors also often recommend cutting down trees that pose obstacles, pointing out that you can replant later. However, it can take decades for saplings to mature. Rather than proceeding recklessly, you’re better off working with the contractor to develop a tree-preservation plan that will protect your property’s beauty and value.
Plan to plan
Before beginning a remodeling project, new construction or any type of excavation, map out the mature trees on your property. Mark each tree’s location and note its species, condition and height and the diameters of its trunk and canopy (the spread of the branches). Draw circles around each tree to indicate the root protection zones.
Next, identify the areas on your property where excavation will take place and where utility lines, trucks and heavy equipment must go. Note the places that are suitable for material and debris storage. Then mark the least intrusive routes for trucks and utilities and the best sites for storage.
Finally, highlight problem areas where you can’t avoid driving over or cutting away tree roots, especially those well inside the root zones. Mark for removal trees that are in the way of construction — or very close to it. Also plan to cut down trees that are in poor condition or diseased. List in the builder’s contract the trees that can be preserved, and mark them on the map as well.
On the job site, post signs and install temporary fencing around all trees that are to be saved. Whether you’re working as your own contractor or you’ve hired a general contractor, be certain that the tree-preservation plan is communicated to all subcontractors before they begin working.
If you don’t feel qualified to complete your own tree-preservation plan, contact a local certified consulting arboriculturist or licensed landscape architect (see SOURCES).
Preservation tips
Taking all possible preventive measures can save a tree from stress and setback — or from the fate of a chainsaw. Before you excavate or even scratch the surface in the vicinity of a tree, consider these recommendations:
• Move it — Rather than cut down a healthy tree that’s in the way, you may be able to transplant it. You can successfully relocate a tree — even one with a trunk as large as 4 to 6 in. dia. — by hiring a professional tree mover. Although transplantation can be expensive, remember that felling, cutting and disposing of a tree can be costly, too — not to mention the price of planting a new one.
• Use alternative tools — Although cutting down trees may allow easier access to the site, it’s not always necessary. For example, boom-supported hoses can sometimes
be used to pour concrete into forms, keeping heavy trucks well away from nearby trees.
• Tunnel in — When laying pipes or cables, tunnel under root masses with an auger rather than cut a trench across roots. A trench that’s 10 ft. away from a 20-in.-dia. tree trunk will wipe out 20 percent to 30 percent of the tree’s root system. Severing roots will also make the tree more likely to topple during a windstorm.
• Provide a cushion — If you must move heavy equipment over roots, put down a protective 6-in. bed of gravel or wood chips. Lay landscape fabric first to make cleanup easier, and remove the material as soon as the job is done.
• Prune preemptively — Trim tree canopies to permit equipment to pass beneath them. This will reduce unnecessary damage to branches and help prevent tree disease later by promoting quick healing. When you have no choice but to dig within the root zone, prune the roots with a sharpened spade rather than tear them with excavation euipment.
• Adjust for grade — To keep soil away from the base of a tree’s trunk, install gravel-filled tree wells around trees when the surrounding grade will be raised. If the grade must be lowered, construct retaining walls to preserve the original grade surrounding as much of the root area as possible.
• Aid recovery — Once the project is complete, aerate trees that have been under stress during construction. The ISA recommends boring 2- to 4-in.-dia. holes every 3 ft. OC to a depth of at least 12 in. and then filling the holes with peat moss, wood chips or pea gravel. Do not fertilize stressed trees during the first year after construction. Most important, irrigate. Be sure that soil drains well and then provide a long, slow soaking with water over the entire root zone once a week if rainfall is inadequate.
Whatever you do, don’t assume a “we’ll take our chances” attitude toward tree survival. Trees can take a long time to die and will be messy and unsightly in the meantime. The cost of eventual removal may be higher because of obstacles added during construction, such as utility lines, plantings, play structures and walkways. The steps you take to preserve an established tree will be worthwhile in terms of aesthetics, energy savings, environmental benefits and property value.
Joe Provey is a free-lance writer from Bridgeport, Connecticut.
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