Do Tree Roots Cause Damage to Sidewalks, Foundations & Plumbing?

Tree roots are often blamed for ruining a lot of things around them. They have been known to lift sidewalks, infiltrate sewage systems, and cause tripping hazards.

But are tree roots the true culprit, or are they taking the fall for the real issue? We investigate. Join us as we get to the root of these issues…

The Suspect: Tree Roots – The roots of a tree have been found in an unlikely location. We know that roots are how plants, including trees, receive nutrients, water, and oxygen. They also help to steady a tree, providing stability in high winds and storms.

Location: Your Yard – Most tree roots remain in the top 18 to 24 inches of soil. Though you may have heard that roots take up about as much space as the tree itself, the truth is that a tree’s root system can be about three times wider than the tree is tall.

Victim #1 – Underground pipes/sewer systems

Issue: Tree roots are accused of breaking and entering the underground pipes and completely blocking the entire system, causing widespread blockages and clogged pipes.

Defense: In roots’ defense, they will not go anywhere that they do not see an opening. So they may have entered the pipes, but that means the pipes were already warped and broken, either from age or from soil movement. The joints of pipes, especially, are vulnerable to failures and breaks.

Solution: The roots, which may have taken up the entire pipe system, obviously need to be removed. Blocked sewers must be cleared mechanically (with additional maintenance required at least yearly). There are also chemical foam treatments available, or, if nothing else works, the ruptured pipes may need to be replaced.

Victim #2 – Sidewalks, driveways, and roadways

Issue: The roots of a nearby tree are causing sidewalks to buckle, roadways to crack, and/or driveways to lift up.

Defense: Most often this is an issue of the wrong tree being planted in the wrong place. We love our beautiful, tall oaks, for instance, but they need a lot of room to grow. If they are planted in the small area between a sidewalk and a street curb, for instance, the roots will not have enough room to properly grow. (See this article for tips on how to choose the right tree for your property.)

Solution: This can be easily prevented by planting trees or shrubs with a smaller root ball in the area, ensuring that there are at least 4 feet (15 feet recommended) between the tree and pavement, or using some kind of barrier to prevent roots growing under sidewalks or roadways.

If it is a mature tree, suggested solutions include moving the sidewalk away from the tree (you’ve probably seen those meandering sidewalks before) to give the roots more room to grow, or creating a bridge over the roots. You’ll see the bridge option a lot in state parks.

Other options include using an air spade to remove some of the soil below the roots to create more room. The sidewalk will need to be replaced in this instance, and a meandering version still might make the most sense.

Some choose to prune away offending roots, but this should be attempted with caution, as roots help a tree remain stable. If the roots are pruned back, the tree may fall, especially in high wind situations. Cutting too many roots or the wrong ones can kill the tree, so root pruning should only be attempted by a Certified Arborist.

You should never pave over the roots of a tree, as doing so will almost certainly kill the tree and lead to many problems in the future. A tree needs water and oxygen to survive, and paving over the roots is like suffocating the tree. If you have to insert a driveway, consider bending it away from the tree (similar to the meandering sidewalks), or using pavers. The pavers are less likely to crack as water and oxygen can still reach the tree roots.

Victim #3 – Building foundations

Issue: The suspects, tree roots, were found at the scene of the crime, invading the foundation of a home through cracks. The roots are being charged with ruining the foundation.

Defense: Roots are almost never the cause of this problem, but they do help highlight it and can add to the issue. As with plumbing, roots will go where they see an opening. Like most things, they take the path of least resistance. If roots are found in a foundation, it may point to a recent drought in the area, as foundations tend to shift when significant amounts of moisture are removed from the surrounding soil. Tree roots can add to this issue as they also remove moisture from the ground (since they need it to survive). Remember that in most instances, however, tree roots remain closer to the surface.

For concrete slab foundations, what generally happens is that the tree roots are seeking water, and find it below the concrete slab. The soil under the slab slumps, and the foundation can crack without the needed soil pressure underneath.

For houses here in the Dayton area, you probably have a home with a basement. In these instances, the foundation is usually much stronger and less likely to crack from the shifting soil around it. It does happen in some instances, though, if too much moisture has been removed from the ground surrounding the foundation. Read more in defense of tree roots here.

Solution: Again, prevention can go a long way. Don’t plant large trees close to a building – ideally, you shouldn’t plant trees within at least 20 feet of your house (see our planting tips for more details).  If you have a mature tree close to your house, be sure that it is well-watered so that it doesn’t have to seek moisture elsewhere.

Other things that can remove moisture from your soil include gardens, poorly insulated basements, and drainage pipes, so oftentimes the dry soil was caused by other things, and the tree took the blame. Check how those other things are working and if they might be causing the soil around your foundation to dry out.

Keep in mind: just because a tree is near to a foundation that is failing does not mean that the tree needs to be removed. A root barrier may be a solution in this case.

Victim #4 – Anyone who has tripped over exposed tree roots

Issue: Tree roots are accused of willfully getting in the way of pedestrians, and occasionally tripping them with their exposed roots.

Defense: Exposed roots usually happen from soil erosion or from frost heaving, where the ground repeatedly freezes and then thaws, pushing roots to the surface. Roots grow in the top few inches of the soil, so this is apt to happen frequently.

Solution: Exposed roots should NOT be cut or covered with soil. Cutting the roots can stress or kill the tree, and covering them with soil can cut off the oxygen supply.

With exposed roots, mulch is usually the best option. Cover the roots with compost or wood chips, but be sure to only use about an inch or two of mulch and make sure that the mulch doesn’t touch the tree’s trunk. (Avoid “mulch volcanoes” at all costs – here’s how to use mulch correctly). The mulch helps retain moisture, keeps the ground from eroding further, and acts as an insulator, protecting against further frost damage.

What do you think?

Now having been presented with the evidence, do you think that trees are entirely to blame for the crimes of which they have been accused? Do they deserve to die/be removed for these issues?

Verdict: The final decision is up to you, but we hope that these facts have cleared up a few things about tree roots, and helped you to root out the real culprits.