October 22, 2016

1 - Tree roots under pavement and foundations can cause problems.

Yard and Garden October 22, 2016

Q.

We are purchasing a home. The driveway and slab in the garage have been lifted by the neighbor's tree roots. The neighbor's tree is a rather large pine-type tree. Is there a way to trench or water jet the roots and then put a barrier so this doesn't happen again? Do you have any thoughts on how to proceed? Do you know of a professional that would be able to come take a look?

- Angie T.

Albuquerque

A.

This is a situation when having a good relationship with your neighbor is important. Since you are just purchasing the home, you may not already have a relationship with your neighbor, but you may want to create that relationship quickly.

Trees are valuable and prized in New Mexico, but they can cause problems in some situations. The answer to your question about managing the roots depends on how close the tree is to the driveway and garage. Since the roots are lifting the driveway and foundation, I assume the tree is very close. That limits what you can do. While it is possible to cut the roots and install a root inhibiting barrier, the end result may be undesirable. If the tree is as close as I am imagining from your description, cutting the roots will significantly reduce the root system and may lead to the death of the tree.

Cutting the roots too closely to the tree can also create a hazardous situation. The roots of the tree anchor the tree in the soil, if they are injured, the tree can fall. A large tree can severely damage your house or your neighbor's house if it falls on the house. A falling tree can also damage vehicles or kill people and pets. Cutting the roots is probably not a good idea.

In answering your question about a professional to personally inspect the situation, I suggest you contact your local NMSU Cooperative Extension Service agent. The Extension agent can see the exact nature of the tree situation and make recommendations. The Extension agent will also know tree care professionals in your area that you may contact. If necessary to hire a tree care professional you will want to contact a tree care professional who is certified by the International Society of Arborists - a professional who has studied proper practices and passed tests regarding appropriate tree management methods.

Another factor to consider is the fact that tree roots cannot grow in dry soil. It is not uncommon for tree roots to grow under a driveway, but the soil under a foundation should be dry, so the roots should not invade that soil. The facts that the roots have grown under the garage slab suggests that there is water under the slab. Why is there water under the slab? Is there a leak? Is the landscape overwatered? Is the property sloping so that water can run under the slab? Or is there a high water table? High water tables are not common in most parts of New Mexico. Foundations slabs often have footers that extend deeply into the soil at the perimeter of the slab, below expected frost lines. This footer should also have been a barrier to water and roots. When buying a house be sure inspections check for leaks and problems that would lead to the problem you have described.

Finally, develop a good relationship with your neighbor because any solution to the tree problem will require both of you to agree on the course of action.

Marisa Y. Thompson, PhD, is the Extension Horticulture Specialist, in the Department of Extension Plant Sciences at the New Mexico State University Los Lunas Agricultural Science Center, email: desertblooms@nmsu.edu, office: 505-865-7340, ext. 113.

Links:

For more gardening information, visit the NMSU Extension Horticulture page at Desert Blooms.

Send gardening questions to Southwest Yard and Garden - Attn: Dr. Marisa Thompson at desertblooms@nmsu.edu, or at the Desert Blooms Facebook page.

Please copy your County Extension Agent and indicate your county of residence when you submit your question!