Got Nature? Blog

Question: Can tree roots cause damage to a home’s foundation? I have a 3’ in diameter pin oak tree that is within 10 feet of my house. A certified arborist took a look at it and said that he would like to use an Air Knife to expose the roots near the foundation (a walkout basement) to determine if the roots are causing damage and/or need to be pruned, or whether the tree needs to be removed since it is situated too close to the house. Before I spend $500 for them to use the Air Knife, I wondered if you thought it would be worthwhile or not necessary.

Answer: Tree roots can damage a house foundation, with an invitation to do so. Tree roots are very opportunistic and will only grow and penetrate where it is easiest to grow such as friable soils and mulch. Typically, when roots encounter solid, impervious surfaces such as pipes, sidewalks, curbs and foundations, they are redirected laterally or up and over. However, if there is a breach or a crack nearby, they can and will exploit those voids in search of moisture. Such as sewer pipes aren’t damaged by the roots, they are just very capable of finding those leaks and moving into the moist and often nutrient-rich pipe.

Roots normally grow horizontally and not very far beneath the soil surface. Sometimes when roots encounter the looser backfill soil near the foundation, they can abruptly start growing down. You may be able to locate these roots, if they exist, by excavating a foot or two down within a few feet of the foundation. If you find a suspect root, cut it off. Unfortunately, in some cases excavation down to the base of the foundation may be necessary. This may have to be done anyway to repair and stabilize it. Cutting the roots should prevent future problems, especially if a root barrier is installed to prevent re-growth.

Resources
Surface Root Syndrome, The Education Store, Purdue Extension resource center
The Nature of Teaching: Trees of the Midwest, The Education Store
Tree Appraisal and the Value of Trees, The Education Store
Construction and Trees: Guidelines for Protection, The Education Store

Lindsey Purcell, Urban Forestry Specialist
Purdue University, Department of Forestry and Natural Resources