Expansive clay soil is common in eastern and central Texas. Its volume is highly sensitive to moisture content. During wet times of the year, the soil expands while dry periods cause it to shrink. This variability causes problems when home foundations warp after the soil they rest on becomes uneven. This soil unevenness is caused by an uneven moisture content. Soil near the edges of the foundation tends to dry out faster than the soil directly beneath the foundation. This causes the soil at the edge to shrink more than the soil at the center which produces a mound shaped profile. This in turn causes the foundation to warp and crack.
How Tree Roots Damage Foundations
Tree roots worsen the foundation problems caused by expansive soil. During dry weather, the soil dries out except for the moisture trapped beneath the foundation of a house. This moisture attracts tree roots which grow toward and under the foundation. They extract this moisture and in the process cause the soil to dry up and shrink. This often causes the foundation to bend toward the tree because the soil under that part of the foundation has shrunk due to the moisture loss to the roots.
This damage usually extends beyond the immediate area of the roots because moisture wicks into the dry region near the roots from the surrounding soil. To give you an idea of how much moisture is lost, a large oak tree can drink up to 200 gallons of water per day. Several smaller trees together use up about 50 gallons per day.
Tree Root Barriers
Tree root barriers block root growth toward the foundation of your house. A trench is dug at least 30 inches deep (the root depth of trees common to the area) between the tree and the foundation. An impermeable material that blocks root growth is placed into the trench. The trench is then refilled with the same soil that was removed. Tree root barriers can be placed even after roots have grown under the foundation. In this case, the roots are pruned at the trench.
A root barrier also helps to restore the levelness of the ground affected by tree roots. After removal of water absorbing roots, the affected ground recovers its normal moisture content, causing it to expand back to its previous state. This re-leveling can be helped along by installing a proper foundation watering system. Attempting to re-level your foundation without a tree root barrier will be ineffective because of the large water consumption rate of trees, especially large ones. Setting up and maintaining a watering system that keeps pace with the thirst of these trees isn’t practical.
If your foundation hasn’t been affected by a nearby tree, placing a root barrier may still be appropriate. A rule of thumb is that roots will extend outward by about the same distance as the tree’s farthest branch. This is a very inexact rule because sometimes roots extend farther. However, this means that if any tree overhangs your house, it will likely become a problem if it hasn’t already.
When Not To Use A Tree Root Barrier
When you have a tree that is older than your house, it means your foundation was built on soil that had adjusted to the moisture requirements of the tree. Building a tree root barrier will disturb this adjustment, causing the area where the roots were to become more moist and to expand. This expansion warps and damages your foundation.
Tree root barriers make sense when your property has trees and you have already spent money on foundation repair. They prevent the problem from recurring. It’s also a good idea to not wait for an expensive foundation problem to happen before installing them.
If you have any questions about whether a tree root barrier is appropriate for your situation, contact us today.