How root barriers can help improve slab foundation performance
A single large oak tree can take 150 to 250 gallons on water out of the ground every day.
No foundation watering system can make up for this much water. Not even close. If a large oak tree overhangs a foundation footprint, using root barriers has to be considered as part of a foundation maintenance program.
Many people find it hard to believe that their beloved trees are a source of foundation movement. Virtually all engineers trained in this area are convinced that trees are a major source of excessive foundation movement. Consider the following email I received from a past client:
About thirty years ago my neighbor planted a live oak tree between our two patio homes about 6-8 feet from my home. Over the years my foundation suffered from the water needs of that tree until there were very wide (1/2-3/4”) cracks above doors, causing them to bind. Sliding glass doors would not close or latch. In the winter when the tree was dormant, the foundation would come up, and then in the summer, the foundation would sink. Slowly, the problem spread to other rooms on that side of the house, even though I had piers and a foundation watering system installed. With the drought of 2011, things got even worse.
Mr. Gray advised removal of the tree as a partial solution to the problem. I was skeptical, believing that it might keep things from worsening, but never thinking that there would be significant improvement in my problem areas. To my complete surprise, once the tree was removed, we saw immediate changes and, over time, the cracks have nearly closed and sticking doors have returned to normal without any additional foundation work.
Trees do affect foundations—much more than I would have ever believed. It was like magic, watching my home rise and become stable. It has been nine months since the tree was removed, and though we have had another fairly dry summer, there has been no recurrence of the previous settlement. I continue to monitor the progress and will soon begin to repair the cosmetic damage.
The video below provides a good introduction to what root barriers are, how they work and how they can allow a foundation to perform in a more satisfactory manner. The following video is a 3 1/2 minute explanation of what root barriers are, how they work, where they are used and when they should be used.
