Concrete Versus Tree Roots


Tree roots are pretty critical to the health and vigor of important shade trees. However, there are times they can cause you concerns.

• If you have tree roots heading beneath the foundation, walk, drive or patio, you can remove one or two per year (October is best time – after hot, dry weather has passed), and you can install a root barrier to prevent regrowth. Hopefully, however, you won’t have to remove the tree entirely.

• Vinyl pond liner (heavy weight) makes a good root barrier. Dig a trench to 16-18 inches between the trunk and the house (perhaps along edge of bed). Trench should be 20-30 ft. long. Lay vinyl in trench, holding several inches above until you have all soil packed back in. Trim flush with soil surface.

• How close is TOO close to the house to plant trees? It certainly depends on the tree species, and it also depends on the house! You wouldn’t want a spreading live oak tree 15 ft. away from a 2-story house, for example, but a more oval/upright cedar elm would be fine at that same distance. Ask your nurseryman.

• As you may surmise from the tip above, I sometimes am more concerned about damage a closely planted shade tree might do to the roof (limbs rubbing) than I am about damage that could be done to foundations.

• How does a shade tree damage the foundation, anyway? It can physically lift and crack even thick slabs of concrete. Roots exert slow and powerful pressure. A mature tree’s roots also take many gallons of water out of the soil every day. In clay soils, that can cause soil shrinkage, cause enough for concrete to fail.

• Can’t you compensate for water that’s lost to trees? Certainly you can, by installing and running a drip soaker hose around the house’s perimeter. However, roots may extend far beneath the foundation, so you may not be able to soak the soil all the way in.

• Anytime you’re dealing with a valuable shade tree, it’s certainly worth the investment of hiring a certified arborist. They “read” trees for a living, and they know how best to help you and your trees – and your house all exist in the same space.

• What about shrubs around the foundation? Can they do the same damage as shade trees’ roots? Probably not. They’re smaller, and they don’t have the same lifting power as huge tree roots can develop. They don’t extend as far beneath the foundation. Don’t be afraid to landscape around your home. Those fears are wildly exaggerated.

Posted by Neil Sperry
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