408 867-0143 | Since 1973 | ISA Certified Arborist
Saratoga Tree Service

Sidewalk Damage by Tree Roots


The problem of walkways and other slabs being lifted or otherwise damaged has reached astronomical proportions. Cities are spending millions of dollars on sidewalk repairs each year. Complexes are perplexed by the costs of replacement driveways and other cement.


The problem seems to only get worse as time goes on. Replacement of cement is perpetuated by newly encroaching roots. It seems that even if the roots are chopped out, it is only a matter of time before they come back and start the damage cycle all over again.


Some of the procedures to stop this problem are so drastic that it seems almost criminal. Municipalities are inundated with old beautiful trees that have out grown the containment areas and in some cases are overlapping the concrete. The shear mass of the trunk caliper is busting out all over causing unbelievable damage.


The sad part of this story is that someone planned this and chose these trees. Now that these trees have created a pristine environment that makes a neighborhood the beautiful shady place to live, the roots create havoc. Potential liabilities spring up all over and not many organizations are willing to live with the gamble. We live in a sue happy society and the trees become the victims of precautionary measures. I’ve seen whole trunks ground back on both sides to make room for the "fix". Roots are treated with little respect and torn out with heavy equipment. Special root cutting machinery is designed to sever everything to make room for different types of barriers. These barriers are designed to "redirect" the new roots that develop after this devastating surgery. Chemical barriers have also been developed to inhibit cell division when new roots make contact.


Trees are tough right? They hardly ever die when these drastic procedures are performed thus perpetuating the concept that it is OK to do this. Similar to the misconception that it OK to top trees because they come back, these practices are ruining these specimens and creating future hazardous trees.


Trees can survive for a long time on stored reserves. If the roots are cut, (even massive amounts of roots), the tree generally survives. But this survival is only temporary. As it takes a long time for a tree to develop and grow large, it usually takes a long time for the tree to die. Some of the potential liabilities created by massive root destruction far outweigh the trip hazard problems. Large trees can stand until the wind decides to get a little stronger than the norm.


If the tree survives the current seasons storms, it is still a candidate for toppling in the future years because the open wounds are starting to rot.


In our efforts to solve the problems of buckling cement we are inadvertently causing future problems of equal or greater liability. If a large tree falls down, structures and vehicles can be crushed. People can be seriously injured or killed. And the turbulent upheaval of a falling tree can lift up and damage the previously repaired side walk


Examples of large old trees with drastic grinding performed many years ago are abundant. Just because they are still standing, and look visually healthy, does not mean that problems are not developing. At the very least, drastic grinding shortens the life of the tree, which In turn requires a removal that maybe should have been considered in the first place. By now, the replacement tree could have developed, and you would be better off. It seems that decisions are often made for the here and now, with little thought of the future. This statement pertains to the choice of new trees as well as trying to get a few more years out of an older, damaged tree. People also get personal attachments to a particular tree, as I am attached to a few of my favorite trees. Common sense should over power these feelings of sentiment when the tree has been damaged by massive root severing.


Alternatives to such a destructive measure need to be addressed. If a community is blessed with beautiful established trees, every effort should be made to try and live in a co-existence with these other living things. All too often the personal feelings of an individual regarding the mess or uplifting growth of roots, condemns the tree to drastic measures or removal. There are better ways to accomplish these same objectives with little damage to the tree. Re-routing the side walk around the tree gives the tree more room to expand, but unfortunately this procedure is not often done. Often because of encroachment on private property, or hazardous traffic situations with protruding curbs. Where possible, this approach should be considered.


Another solution, though temporary, is adding material to the raised edges, such as asphalt, to lessen the trip hazards. Grinding down the raised edges is also an inexpensive temporary fix. Another possibility is to add fill, and re-pour in a way that develops a mounded walkway. Once again, as the roots continue to grow larger in diameter, the lifting problem will resume.


A suggestion that was recently brought to my attention, that seems to make sense, is to pour a smaller section, over the damaging roots, with separations that limit the amount of damage for easier repairs. When a three foot section is all that needs replacement, it is easier and less costly to fix, than a larger continuous walk.


Careful selective removal of surface roots with a sharp ax, after the cement has been removed, will slow down the lifting problem with little damage to the tree.


Selective removal of the offending roots is much more desirable than complete destruction to stop all the roots. The roots that are six inches or more under the slab, generally cause very little lifting, and should not be eliminated. Even the roots that are closer to the slabs underside, don’t necessarily need to be cut out. Loosening the soil above the root before pouring, will allow more compression room before causing lift.


Another great suggestion is adding an underlayment of a compressible material such as a two part pourable polyurethane foam. If one inch of foam is between the roots and the slab, the roots will compress into the foam for a longer period of time. This method has it’s limitations. If heavy vehicular traffic is driving over the slab, the foam may not be adequate support, but on walk ways, there should not be a problem.


None of these suggestions is a cure or a complete stop to the problem at hand. All of these suggestions are keeping the needs of the tree in mind. I feel that where large established trees are to be left in place, an attitude adjustment is needed. There is no perfect answer to a problem that was caused by improper planning in the first place. You can’t expect a large variety of tree to conform to an inadequate growing space. A decision must be made to either live with the trees growth by careful co-existence, or start over with proper varieties in the first place. Don’t destroy the tree and hope for the best. Take a good hard look at the benefits these trees give us, before you complain about the problems these trees cause. You might find that the loss in your own environment is greater than the problems caused by the trees normal growth habits.


Proper planning is the only answer. Sadly, this planning does not pertain to the pre—existing mistakes of past tree choices. Future tree planting efforts are much more thought out. We now know better varieties for tight planting areas. Root barriers are being put in, as a preventative, rather than a desperate effort after the fact. Common sense thinking about growth patterns can help save money and needless repairs. Of course, by the time these trees get big, they will be someone else’s problem anyway. (OUCH)!




Like a tree, this site is growing. Check back often to see how we are evolving.