The structural engineer who inspected my foundation Monday is recommending a root barrier be installed in a back corner of the yard to keep roots from a nearby live oak tree away from my concrete slab.
They are also called root walls and root caps. The idea is to cut any roots that are reaching under the foundation, then put something in the ground between the tree and the slab to keep the roots from returning.
The hope is that by keeping the tree from drawing moisture from under the slab, the clay soil will re-hydrate and give the foundation in the back of the house some lift. Not much, but some. The tree is 12 feet from the corner of the foundation.
The engineer also recommends calling in an arborist to make sure we send the root barrier deep enough to thwart the roots of the particular species of tree…in this case a live oak, and also to advise us in how to do this while inflicting the least amount of damage on the hapless tree.
The specs for the root barrier are certainly conservative and to me bordering on overkill. It is to be 25 feet long, ok, three feet deep, er, ok, and if done with concrete, A FOOT THICK. Yikes! The concern here is roots, not bullets.
The recommended alternative to concrete is a really thick plastic barrier at least 20 mil. However using plastic is termed a temporary solution, lasting no more than ten years. The engineering report listed a couple of sources from where to fetch such material.
The thing that I found out in calling around for estimates is that not a lot of arborists or tree companies have much enthusiasm for root barriers. I was referred to foundation repair contractors. To be sure, there is debate about how much harm tree roots really do to a foundation and the tree folks tend to side with the trees. Understandable.
As it stands now, I’ve emailed the specs to one foundation repair company that does barriers and another is supposed to call Monday to set up a time for an estimate. Stay tuned.