extract from web.
The root system of a mature crabapple tree is neither aggressive nor invasive. Crabapple roots are not known to break or grow through home or building foundations unless the foundation is already cracked or leaking. Crabapple roots are generally surface roots, with a few sections that penetrate deep into the soil. Because crabapple varieties include trees of all different sizes, the size of the root system depends on the size of the tree.
To determine the size of your tree’s roots, measure the distance from the trunk of the tree out to the dripline. The dripline is located under the edge of the outermost section of the tree’s canopy. Feeder roots, which extend the furthest from the tree, typically extend two to three times this distance. For example, if the dripline is 8 feet from the trunk of the tree, the roots will likely extend 16 to 24 feet from the crabapple’s trunk."