Arizona ash trees
The roots on this mature Arizona ash tree are getting close to the house and I'm afraid the may disrupt the slab. I don't want to loose the tree so I was wondering if I could kill the outer most roots that are danger ing the house and the tree would not be affected.
Daniel; Lateral roots more than 12 - 15 feet from the tree trunk will not likely lift or crack a substantial concrete house foundation. But they can undermine, lift and crack a less substantial structure like a garage floor. Of course un-reinforced slabs, garden walls and headers are more vulnerable.
You can probably get away with cutting a limited number of the lateral roots without severely harming the tree. Root prune with clean cuts, don't poison them with herbicide or the chemical could translocate into the parent tree and cause harm.
Install an 18" to preferably 24" deep root barrier to retard re-growth of the roots in that direction. I believe that plastic/composite root barrier material is available at home improvement and garden supply stores like Home Depot and Lowes.
Some things to keep in mind: cutting a large percentage of the root system can affect the physiological health and sometimes the structural integrity of the tree. Roots are there for uptake of water and nutrients.
The closer you cut to the trunk, them more potential for harm and for destabilizing the tree, making it vulnerable to wind-throw toppling.