If you have a lot and are planning on building a home on it, take some time to examine your existing trees and any plans for future trees. Trees could pose a problem for your home if their roots grow underneath its foundation.
When tree roots grow underneath your home, they can suck all the moisture out of the soil and cause the soil to dry out and shrink, which can cause a condition known as differential settlement.
Differential settlement occurs when the part of your house that sits atop dry, compacted soil sinks while the part of your house that sits atop moist, expanded soil remains level. When one part of your house sinks, its structure can become seriously damaged.
One way to defend your new home against differential settlement is to install one or more root barriers around trees before you build on your lot.
What Are Root Barriers?
Root barriers are physical underground walls that are placed to inhibit or direct tree root growth and prevent tree roots from growing up underneath your home. Broadly, root barriers are used to deflect the growth of tree roots in a different direction or deeper into the soil, where they will cause less damage to your home, sidewalks, and curbs.
For young trees, root barriers can be set up a certain distance away from the root systems to guide the natural growth and direction of roots as the trees mature.
For mature trees, which may need to have their roots cut, root barriers deflect the growth of new, regenerated roots from the cut end. That way the roots won’t simply grow right back into the areas from which they were cut.
3 Kinds of Root Barriers
There are three kinds of root barriers: physical, geo-textile, and chemical.
Physical root barriers are solid walls, typically made up of 90-degree, raised rib plastic panels made of polyethylene, polypropylene, or polystyrene. Physical root barriers can also be made of poured concrete.
Because physical root barriers are either totally or mostly impermeable, they have the added benefit of doubling as moisture barriers. Moisture barriers can be important for maintaining more constant moisture levels around your home’s foundation.
Geo-textile root barriers are made of heat-fused nylon mesh and typically requires support, such as proper backfilling, to stand vertically.
Although these kinds of root barriers can be effective, some plant and tree species actually engage or escape in the fabric. Still, because geo-textile mesh can offer an ideal rooting surface, it may also encourage roots to grow deeper by creating deeper corridors in the soil that have greater oxygen availability.
Some fabric root barriers contain chemical herbicides that impede root growth by burning off root hairs. The chemical is either heat-bonded to the fabric or attached to the fabric in pellet form. The chemicals are usually non-toxic and do not leech into the soil. Like geo-textile barriers, chemical barriers need support to stand vertically.
Controlled-release chemical barriers work best, as single-application barriers release too much chemical initially and then weaken rapidly over time.
A word of warning: if you use chemicals to limit the growth of a tree’s main root system, you’ll need to increase irrigation so that it can develop higher-density feeder roots to compensate.
Root Barrier Installation
Installation of root barrier systems is pretty straightforward:
- Dig a trench in the ground between the side of trees or other plantings and the home, sidewalk, or curb you’re looking to protect
- Install the root barrier
- Cover up the trench
Plastic root barrier panels are connected by couplings, strips, or glue in a linear fashion. Concrete root barriers are simply poured in the ground. Fabric geo-textile and chemical barriers are rolled out and laid out in the trench.
While some guides recommend installing root barriers between 12 and 24 inches deep, other sources recommend installing three feet deep (36 inches) so that the barrier ends up at least one foot deeper than your foundation.
Root Barrier Life Expectancy
While it may seem like a lot of work to install a root barrier system, the good news is that physical barriers made of plastic or concrete should last indefinitely.
If you go with a chemical barrier, you can probably expect a lifespan of about five years. Just keep in mind that the amount of water that your yard gets will strongly influence that figure. The more water you get, the shorter a chemical barrier will last.
Why Root Barriers Should Be Installed Before Building
Many people wait until they have a problem to install a root barrier system. But take it from us, you don’t want to wait until part of your home starts sinking and you’re on the verge of serious structural damage before you install a root barrier. Instead, plan your system at the very beginning, before you build on your lot.
Contact Frankel for questions about whether you should develop plans for a root barrier system before building on your lot.