While they don’t move very fast, tree roots are the “root” of many home and yard problems. If you see them encroaching on your foundation, driveway, or a public sidewalk, don’t remove the tree or damage its extensive root system to stop it – put in a root barrier!
A barrier will redirect roots away from your home or strangle them before they can get too close, all while keeping the tree’s nutrient system intact.
Why Tree Roots Spread
Trees grow their roots in all directions to find moisture; if they can’t find anything close by, these roots can go a very long way. They might encounter an obstacle – your foundation perhaps, or a 
sidewalk or walkway; if this is the case, they will penetrate the porous concrete and break down the material. Roots can also take too much moisture from the soil, causing the ground to shrink and the foundation to settle. If overgrown and expanding roots continue on their path, the property owner can see expensive repairs in their future.
It’s a feedback loop – even as they dry out the soil, large trees and shrubs will spread their roots out in search of moisture. Until they find it, they will keep expanding. To prevent encroachment, make sure your tree is properly watered and install a root barrier. When installed correctly, the barrier will direct any roots downward and away from your concrete or garden.
Making A Root Barrier
The most inexpensive and effective check on extensive root systems is a manufactured deflector. This usually consists of a thick, sturdy polypropylene sheet that acts as an impenetrable barrier, preventing the expansion of root growth. This “wall” can double as a barrier to prevent excessive dampness and moisture from the surrounding soil.
Another type of barrier is a root trap or screen. This is made from metal screens, welded fibre sheets, or woven fabrics, and the trap should have holes large enough to let the root tip to grow through, but strong enough to prevent the root from growing any further.
The final common root barrier is a fabric with herbicide. This is a textile that is covered with a chemical root growth inhibitor, often cupric carbonate or trifluralin, an herbicide that inhibits root tip expansion. Both are effective, but the barrier will lose their effectiveness over time, depending on the soil temperature and moisture conditions.
Setting Up A Root Barrier
To install a root barrier, measure how far away from the plant or tree you need to dig the trench, using three times the trunk’s diameter as an estimate. Next, determine the number of panels or length of cloth you need by measuring the length of the planned barrier; if you’re using panels, divide that by the width of your panels. Most options on the market are 24 inches long.
Once you know where the root barrier will go, dig a narrow trench about 30 inches deep and 3 to 4 inches wide to accommodate most panels (some panels have ribbing that could need a wider trench). Slide the panels into the trench, making sure the top is at least one inch above the ground so that the roots don’t try to grow over the barrier. Backfill the trench, pouring water into it to compact the dirt.