I have a retaining wall approximately 18 inches high on the street side. As it goes around to the sides, it decreases in height until it is about 6 inches on the house side. A water oak tree is in the front right corner on the tall side. The landscape ties the wall is made from is rotting and I need to replace it. Feeder roots have grown out beyond the wall. I want to use stones/bricks so that it will be stronger and won't rot. How can I place the stones level across the roots and not jeopardize the tree? The landscape ties are across the roots currently and have been for the last 19 years (replaced a few times).
You have quite a project ahead of you.
Your trees roots have all ready impacted the existing retaining wall and now the new project and all your work may be damaged by the tree roots continuing to grow.
I do think this is an area to call a professional in order for your tree and your new retaining wall to have the best outcome.
I have a couple of great links for you to help you get started.