Trees are typically considered practical and enjoyable additions for the positive effects they have, which may include improved aesthetics, reduced energy use for heating and cooling and environmental benefits. Trees growing near a house or other structures, however, may pose a threat to foundations and other structural elements. Although the best root damage prevention method is to plant only vegetation that is unlikely to produce intrusive roots and to leave adequate space around the slab, this can be difficult to observe if the tree is already established and prized in the landscape. Steps can be taken to discourage roots from growing under the slab.
Discourage root growth near the slab. Do not water or fertilize the area of the landscape between the tree and the slab and make sure that water drains away from the slab quickly. If an awning or roof-line extends well beyond the slab, it may be keeping the soil around and under the slab dry enough to discourage tree roots.
Install root barrier cloth around the slab or the tree's root system by digging a deep, narrow trench and inserting the barrier. Some commercially available root barriers act as solid deflectors while others contain herbicides that deter roots. For barriers to be effective, they must be installed deep enough and have no breaks that allow root penetration. Follow manufacturer instructions for proper installation, including depth.
Remove the tree entirely by cutting it down and treating the stump with an herbicide to prevent re-sprouting and ensure root death. Although this is generally a last resort, it may be warranted so as to prevent structural damage if the tree is a species that tends to produce damaging roots or is sufficiently close to the slab. Alternatively, a homeowner may elect to sever only large roots growing toward the house. This method, however, may still result in tree death or severe damage and potential limb breakage.