Tree Root Causing Foundation Problems

How Tree Roots Affect Your Foundation

• The obvious foundation problem tree roots cause is when the roots, which grow outward searching for water and nutrients, are close enough to your foundation that they push against the foundation wall, causing it to crack or move inward. A large tree on one side of your home can also cause the soil on that side to settle more rapidly than the opposite side. This is because the roots absorb the moisture in the soil, making it significantly less on the tree side. The soil shrinks as it dries and separates from the base of the foundation. When the resulting void becomes large enough, the foundation may collapse to find support, causing cracks to form.

Root Barricades

• Root barricades are typically made of polyethylene sheets and installed in the ground to a depth of about 30 inches. These are designed to stop the roots from taking moisture from the soil that is around your foundations. Root barricades are not ideal if the tree is older than the foundation because older trees and their roots are part of the moisture table in the soil around your home. Removal may cause heaving and severe damage to your foundation. It is also not recommended to use root barriers in cases where the soil on the tree's side of the barrier does not provide the moisture and nutrients the tree needs to thrive.

Preventing or Stopping Soil Movement

• During periods of drought, trees cannot go dormant as other plants do, so they will continue to draw moisture from the soil, causing it to become dry. Watering trees near your home's foundation on a regular basis to compensate for periods of drought can limit soil movement around your foundation. Irrigation systems below ground are the most effective method of preventing soil movement, but can be expensive to install and maintain. Surface watering is also effective if done consistently. In clay soils, water absorption is slow and over-watering is possible, so water only as the soil begins to dry out and don't localize watering just at the base of the tree. The entire root system must be covered. The larger your tree, the more water is required. Pruning can also reduce the amount of moisture your tree requires. By pruning you reduce the tree's mass, which lowers its nutrient requirements. To avoid damaging the tree, prune on a two- to five-year cycle and never remove more than 30 percent of the tree's branches.

Modifying Root Growth

• Tree roots grow in the direction of least resistance and where water, air and nutrients are readily accessible. The roots can be encouraged to grow away from foundations by ensuring that the tree has ample room to grow on all other sides and by modifying the soil around these areas so that it is nutrient-rich and aerated. In comparison, the soil near your foundation should be modified so that it provides poor growth conditions. This is done by compacting the soil, adding impervious surfaces such as concrete, or withholding nutrients the tree needs.