Hello, Raymond here, your certified professional home inspector. I wanted to write about trees being too close to your home’s foundation, your biggest investment. Too often trees are planted to close to the foundation of the home. Tree roots and shrubs can be the source of foundation problems. Trees withdraw large amounts of water from the surrounding soil and in areas of expansive soils this could lead to foundation settlement. Also, bushes and trees can cause damage to the siding and roof if they are not trimmed.
Any reputable home inspector understands that the Houston and surrounding areas are home to large areas of expansive soils, which expand in volume when wet and shrink in volume when dry. This process happens many times and can cause horizontal movement, vertical movement, uplift, heaving and soil movement. This can lead to cracks and damage to your foundation. Usually the moisture content of the soil under the center of the foundation remains stable. Usually it is the soil around the perimeter of the home that is exposed to large volumes of rain and long periods of drought. The swelling and shrinkage of the soil can cause portions of the foundation to rise and fall.
Tree roots and shrubs can cause problems to the foundation when too much water from areas near and under parts of the foundation are absorbed by them. Tree roots can usually extend outward to the end of the tree canopy and up to three times the height of the tree. A tree about one foot in diameter and twenty-five to thirty feet in height can absorb approximately 150 gallons of water per day. If this tree is close to the foundation, then the water absorbed by the tree and evaporation during the extreme dry months can leave the soil in that area much dryer than the soil under other areas of the foundation. This can lead to differential settlement to the foundation. This is why your real estate home inspector advises to plant trees away from you home.
In most cases the solution for tree roots and the risk of foundation problems is to remove the tree and or install tree barricades. A general guide is that a large tree should be no closer than ten to twenty feet to the home foundation. Trees that are closer than this guideline should be considered for removal. However, sometimes there are exceptions. When a large tree is very old, the removal of the tree may cause a large void under the foundation as the tree roots gradually die and decompose. If you have a situation like this, an arborist should be consulted to determine the correct course of action.
Tree barricades can be good solutions to keep tree roots from causing foundation problems. Generally a trench is dug about five feet from the exterior foundation. A series of overlapping sheets of Plexiglas is placed in the trench to a depth of 30 inches. This will prevent the tree roots from growing toward the foundation and withdrawing significant amounts of water.
Trees can very nice to have on your property, just make sure they are not adversely affecting the condition of your foundation. Also, keep safety in mind when removing or trimming trees. It is recommended to contact a qualified contractor or an arborist, when you have medium to large trees.