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Friday - February 17, 2012

From: Audubon, NJ
Region: Mid-Atlantic
Topic: Pruning, Trees
Title: Roots in foundation of home in Audubon NJ
Answered by: Barbara Medford

QUESTION:

I live in an old house (almost 90 years old), and within the past year I have noticed in one area the concrete basement floor breaking. Today I finally made time to investigate. In these old houses it was fairly common to only have concrete 2" thick in the floor. When I removed the broken pieces I found a root 2" to 3" in diameter that caused the floor to break. There was a large black walnut tree more than 35 years ago that was removed, but now there are two silver maple trees (about 40 years old) in my neighbors yard that are about 45' from the floor fracture. The roots are green (wet) so I assume they are from the Maple Tree. I plan on cutting the root, but is there any more permanent solution to the roots? Quite frankly I could care less about the trees that are messy with leaves and spinners that the neighbor does not take care of.

ANSWER:

We have no way of knowing where those tree roots originated. An expert, on the spot, could probably recognize the species of tree from the root, but we are neither experts nor on the spot. This article from the Morton Arboretum Tree Roots and Foundation Damage explains the problem far better than we can. The main point of the article is that the tree roots didn't start out to destroy your foundation; it started out looking for water. When the roots came to your foundation, they dipped down below the house looking for moisture. Having found it, they have a nice drink, pulling water out of the soil, and causing the soil to subside. The soil, which is the support for your house, started shrinking and, without that support, the cement started cracking.

If no sprouts of the long-removed black walnut tree survived, we think it can be exonerated from the blame. The maples, even 45' away from your foundation, are notorious for invasive roots. There are 12 members of the Acer, maple, genus native to New Jersey and we chose Acer rubrum (Red maple) as an example. If you follow the link to our webpage on the red maple, you will learn that it has high water needs, is know for invasive roots, and grows to heights of 40 to 60 ft. in cultivation.

A tree that grows very tall is going to need lots of space under ground (and not very far down from the surface) to gather sufficient nutrients from the soil, storing water and, perhaps most importantly, anchoring that tree in the ground. You have heard the expression "top-heavy" we are sure; apply that to a large tree and you can perhaps visualize a tree that topples in a wind or even if someone leans against it. And with an instinct for survival, tree roots stand up for themselves, or perhaps we should say "push up" because they will push up sidewalks and driveways, as well as crack foundations in search of water.Remember that roots are radiating out in all direction from that trunk for as much as 2 to 3 times the width of of the top of the tree.

So, it's reasonable to blame the maples in your neighbor's yard, but you can hardly make them cut down trees on their property, even though there is a good chance those roots are affecting structures on their property as well.