Problems With Concrete Over Tree Roots – What To Do With Tree Roots Covered In Concrete

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By Darcy Larum, Landscape Designer

Years ago, a concrete worker I knew asked me in frustration, “Why do you always walk on the grass? I install sidewalks for people to walk on.” I just laughed and said, “That’s funny, I install lawns for people to walk on.” The concrete vs. nature argument is not a new one. As much as we all may long for a lush, green world, most of us live in a concrete jungle. Trees, who have no voice to join the argument, are often the biggest victims of this battle. Continue reading to learn about concrete over tree roots.

Problems with Concrete Over Tree Roots

Concrete workers are not arboristsor landscapers. Their expertise is in laying concrete not growing trees. When a concrete worker is at your home giving you an estimate on a driveway, patio or sidewalk, that is not the right time or the right person to ask how the concrete will affect trees near the project.

Ideally, if you have large trees that you would like to keep safe and healthy, you should first call an arborist to come tell you the best location to place a concrete structure without damaging the tree roots. Then, call a concrete company. A little planning ahead can save you a lot of money in tree removal or redoing concrete.

Oftentimes, tree roots are pruned or cut to make way for concrete areas. This practice can be very bad for the tree. Roots are what anchor tall, top heavy trees in to the ground. Cutting major roots that are anchoring a tree can cause the tree to easily be damaged by high winds and strong weather.

Roots also absorb water, oxygen and other nutrients that are essential to tree growth and development. If half a tree’s roots are cut off, that side of the tree will die back from lack of water and nutrients. Cutting roots can also lead to insects or diseases penetrating the fresh cuts and infecting the tree.

Root pruning is especially bad for older trees, although young roots that are pruned to make room for concrete patios, sidewalks or driveways may grow back.

What to do with Tree Roots Covered in Concrete

Tree roots covered in concrete will not be able to absorb water, oxygen or nutrients. However, professional concrete workers do not usually pour concrete directly on the bare ground or tree roots. Generally, a thick layer of gravel paver base and/or sand is put down, compacted and then the concrete is poured over this. Sometimes, metal grids are also put beneath the gravel base.

Both metal grids and a layer of compacted gravel will help tree roots grow deeper, avoiding the gravel or grid. Metal grids or rebar used when pouring concrete also help prevent large roots from being able to heave the concrete up.

Oops, I poured concrete patio over tree roots by accident…now what?! If concrete has been poured directly upon the ground and tree roots, not much can be done. The concrete should be removed and re-done properly, with a thick paver base. This should preferably be away from the tree’s root zone. Care should be taken to remove any concrete from the tree roots, though the damage may already be done.

A close eye should be kept on the overall health of the tree. Trees do not usually show signs of stress or damage immediately. It can often take a year or two to see the effects caused to a tree.

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