Archive for August 4th, 2011
Root of foundation issues may have nothing to do with tree
The Garden Guru: Root of foundation issues may have nothing to do with trees
by Neil Sperry, star-telegram.com
July 29th 2011
It happens every time we have a serious drought: Trees get blamed for foundation, walkway and driveway problems, and people start removing some of their most valuable landscaping assets.
Well, just a moment there, Nellie. Before you take an axe to the apple tree, let’s be sure it’s actually the culprit.
We’ll begin with a little lesson in soil science. Stifle the yawns — we’ll do it in one paragraph. The black clay gumbo soils that cover most of North Texas are extremely expansive and contractive, and it’s all driven by moisture. That means that they’ll expand when they’re wet, and they’ll contract when they’re dry. “Contract,” as in cracks wide enough to lose small pets. The counterbalance to that is that those same soils will swell when they’re fully imbibed with water during the inevitable rainy seasons.
As the soils go, so go our foundations. All of that expansion and contraction puts slabs of concrete under incredible stress. Cracks begin to develop. You’ll see the issues crop up in mortar joints, and you’ll notice them in wallboard and tile floors. Doors and windows won’t operate properly.
And that’s about when the subject of tree roots enters the picture. You’ll be told that it all can be traced back to the plants’ roots, and you may even be told that the plants have to come out.
As is shouted on late-night TV, “But, wait, there’s more!” The fact that goes missing is that those roots are there in all conditions, from drought to flash flooding. Yet the foundation problems only show up when it’s dry. So don’t you think that the soils might be at least partly to blame for the foundation troubles?
If you’re concerned about possible structural problems in your house, retain a dependable foundation-repair specialist for your home inspection. Then hire a certified arborist for a second and concurrent opinion. It may very well be that tree roots are part of the cause, but the arborist may have suggestions of ways to save the trees so that they and your foundation can coexist. It may involve severing roots that have grown directly beneath the concrete. It could mean the installation of a subsurface barrier to prevent further root growth. The arborist may decide that the tree is far enough from the slab that no roots of any significance are involved.
Slow-drip irrigation applied through soaker hoses laid just a few inches from the concrete will help keep the soil hydrated (or “swollen”). That will mitigate the moisture pulled out of the ground by the tree’s roots. Cover the soaker hoses with a couple inches of mulch, and you’ll reduce the soil-to-air contact. That will help keep the soil from drying so quickly.
You can also get a pretty good handle on the number of large roots that might be involved by inserting a rod (probe) into the ground along your foundation. Stick it in every couple of inches, and you’ll be able to determine where the roots are. Once you find them, dig to see how large they are. If you do need to remove them, that’s work that’s best done in October, after the worst of the hot, dry summer weather has passed.
Protecting roots during construction
Still the advocates for our shade trees, let’s also step to their rescue when we have to make changes in the trees’ surroundings. If 90 percent of any tree’s roots are in the top foot of soil, as we so often hear, then take great pains to protect them when construction is done anywhere near them. Do not add soil that will cover more than 10 or 15 percent of a tree’s entire root system. Install a retaining wall to hold back the new soil, and let the well you create cover a large percentage of the tree’s original root zone (hopefully all of it). Again, a certified arborist can guide you.
Don’t cut utility trenches across them. Think of the root system as a wagon wheel. Don’t cut across its spokes. Pipes and wiring don’t cost very much compared with the value of a large shade tree. Run them around its perimeter. If you must install sprinkler heads or wiring for landscape lighting, dig in from the outside, more or less parallel to the roots.
A large and vigorous shade tree of a quality species can add thousands of dollars to the resale value of an urban property. Think twice about sacrificing that tree when problems arise. Get all the facts by hiring a tree specialist.
Neil Sperry publishes Gardens magazine and hosts Texas Gardening noon-1 p.m. Saturdays and 9 a.m.-noon Sundays on WBAP AM/FM. Reach him during those hours at 800-288-9227 or 214-787-1820.
Original Page: http://www.star-telegram.com/2011/07/29/3253921/the-garden-guru-root-of-foundation.html#tvg
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