Damage of Structures due to Tree Roots

There are two main forms of damage due to tree roots. The first involves the growth of tree roots beneath sidewalks, patios, roads, and block walls, where the physical increase in size of growing roots causes uplift and differential movement of the structure. The second type of damage is from tree roots that grow beneath shallow foundations. As the tree roots extract moisture, the clay shrinks and the structure settles. For tree‐root uplift, it is observed that damage more frequently occurs to lightly loaded structures. Damage seems to be less severe for soft or loose soil that can deform as the roots grow, rather than dense or hard soils such as road base. For the example of tree‐root shrinkage presented in this paper, a large Pepper tree caused significant desiccation of the upper 2 ft (0.6 m) of a very highly expansive clay deposit. Laboratory tests recorded expansion of the desiccated clays when they were given access to water. Two solutions to the problem are to plant the tree well away from the structure or to use deepened perimeter footings to restrict roots from gaining access beneath the foundation.