Construction Damage

Construction Damage Kills Trees

Construction Damage is any injury that occurs to a tree during or because of any construction process, including demolition, site preparation, or building.

Trunk and Canopy Damage

You can see on the trunk where there is an old scar from previous construction damage. In the foreground of the photo is recent damage where roots have been cut. — Figure 1. This elm has been abused in many ways over the years. You can see on the trunk where there is an old scar from previous damage. In the foreground of the photo is recent damage where roots have been cut.

Trunk and canopy damage is evident and promptly noticed by the property owner. In some extreme cases, construction damage is severe enough that trees may die almost immediately. Broken branches or scrapes/missing bark on the trunk are telltale signs of past construction activity (Figure 1). Usually, trees will recover from these types of injuries if they are small; however, each wound allows microscopic decay organisms to enter the tree, creating a potential for future problems. Construction equipment striking the tree and damaging the cambium layer on more than 50% of the tree’s circumference can cause rapid death.

Prune broken branches to speed recovery and enhance aesthetic appeal. Trunk wounds cannot be repaired once they occur, but they should not be painted with wound paint, as this will actually cause more harm than good.

Root Damage

Construction damage most often affects tree roots and is hard to diagnose. Most damage goes unnoticed and causes a slow decline over many years (5 to 10). Symptoms manifest slowly, so property owners don’t draw the connection to the construction.

Root Facts

A common misconception about roots is they are located deep in the ground, but 50% of tree roots occur within the first foot of soil.
An astounding 90% of all tree roots are located in the top 3 feet of soil.
Roots extend 2-3 times past the drip-line of the tree.
More than 60% of the fine-absorbing roots occur outside the drip line.

Let’s dig a little deeper into root damage.

Severed roots

Construction Emporia Topeka Kansas city Lawrence — Figure 2. This maple tree had structural roots severed during grade reduction for a parking lot. Notice the mechanical scrapes on the root flares. This tree was removed a few weeks after this photo was taken because the entire tree was starting to lean into the house behind it.

Trenching and digging equipment will sever roots, as will lowering the soil grade. The closer to the tree roots that are cut, the less likely a tree is to recover. Large roots cut inside a distance of approximately 4-5 times the DBH (diameter of the tree at breast height) are structural roots. When multiple structural roots are cut, trees become unstable and unsafe. These trees should be considered for removal since the anchors have been cut (Figure 2). For example, if a tree measures 22 inches in diameter the structural root zone will be around 8-10 ft radius. Roots cut in the structural root zone greatly increase the likelihood of tree failure.

Impact of cutting Roots

Expect recovery when less than 20% of the root zone is impacted on healthy trees.
Cutting 20-40% of roots typically causes dieback.
Cutting roots higher than 40% will usually cause tree death.

Recovery and survivability depend on the tree species and the tree’s condition before the damage occurred.

Suffocated roots

Fill and compaction suffocate tree roots.

Construction Emporia Topeka Lawrence, Kansas City — Figure 3. Construction activities create “hydrologic discontinuity” (fancy words meaning the water flow has been disrupted or altered). This standing water around this sweetgum tree can cause roots to suffocate, resulting in tree decline.

Construction Damage Emporia Topeka Lawrence Kansas city — Figure 4. Soil piled around trees can suffocate roots and compact the underlying soil.

Fill soil is material brought in to change or level the grade after construction. This alters the soil respiration rate. Most tree roots are in the top 12 inches of soil because the gas exchange is better closer to the surface. Fill and grade changes limit gas exchange with the atmosphere and can suffocate roots. The structure and composition of fill can also alter soil hydrologic components (Figure 3).

Even temporary soil piles can smother the tree’s roots. Remove fill located around trees and return the soil to its original grade to the drip line of the tree. (Figure 4)

Soil compaction occurs when people, equipment, and supplies compress the soil’s pore space (Figure 5). Healthy soil has roughly 50% pore space. Compacted soil dramatically reduces pore space, reducing fine root development, and limits the amount of water available to the tree. Compaction also reduces the soil respiration rate. Reduced respiration causes stress on the tree, but the process is usually slow, so damage will not show until years later. This is problematic because the time gap between construction and damage makes it hard for homeowners and contractors to connect the construction to the tree decline. Most contractors are unaware of the damage they cause.

Some soils compact more easily than others. Wet soils and soils with a high clay content are more susceptible to compaction.

Construction Damage Topeka and Emporia Lawrence Kansas City — Figure 5. This house was built with the intention of saving the clump of elm trees in the front yard. Elms are usually pretty tough but the amount of soil compaction will likely kill this tree. Soil compaction can be a chronic problem and this may affect new plantings for years to come.

Prevention is imperative

Prevention is the best way to keep trees healthy during and after construction. Wellnitz Tree Care can help you develop plans based on the tree species, age, condition, etc., to protect your tree from construction damage. We follow the American National Standards Institute guidelines (ANSI A300 part 5) to help establish tree protection zones and proper construction procedures around trees. Our practices help minimize damage and mitigate it after construction if encroachment occurs within tree protection zones. We work with contractors throughout the process, from planning through post-construction and landscaping.

Construction Damaged Trees

Wellnitz Tree Care helps trees previously impacted by construction activities, provided the damage is not too severe. Our certified arborists can alleviate soil compaction with an Air Spade or by vertical mulching. Products such as Cambistat can aid in fine root regeneration if roots have been severed. Unfortunately, some trees we just can’t help. If this is the case, we can remove the trees and grind stumps. Wellnitz Tree Care can even help recommend a new tree.