Trees growing near a home are often a source of worry to a homeowner, mainly because of the roots. And while tree roots can do damage to a home's foundation, it's probably not for the reason many believe. Those roots, in fact, won't be able to push through the foundation, buckling it in spots. Rather, roots can rob the soil near the foundation of crucial moisture. Soil subsidence and loss of key foundation support then develops.
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House foundations depend on the surrounding soil for support to keep from bowing outward, for instance. Ideally, the soil was dense to begin with and then compacted when the foundation was laid, but it may not have been. Some soils have a lot of sand, which can mean they need moisture to maintain their solidity. When they're deprived of that moisture, they can start settling, leaving the foundation in that area with less support.
The roots of a tree just aren't able to push their way through foundation walls and are often easily turned away by simple barriers. However, they do remove a lot of moisture from adjacent soil. Also, as they grow larger over the years they can further loosen soil, heaving some of it out of their way. As a result, a pressure imbalance develops between the soil and the foundation, leading to outward bowing.
In many cases, tree root systems that have managed to create soil settling or subsidence are within 16 feet or so of a home. Remember that tree roots grow outward to search for water. If you keep any trees, bushes and shrubs near your home properly watered, there's little chance of them creating problems. Usually, those within 20 to 30 feet of your house will benefit the most from regular watering.
House foundations act as effective root barriers. However, roots will continue to search for water. And they may go after your underground water pipes if there are any leaks. Also, certain species of tree are more thirsty than others, especially if they're larger types. These include oaks, which have extensive root systems. If you plant a tree near your house, try for at least slightly farther away than half the width of its maximum branch spread at maturity.
- Renegade Gardener: Myth of the Week 2007: "Tree Roots Can Grow into a House Foundation ... Damage"
- The Telegraph: Will Tree Roots Damage My House?; F. Cutler, et al.; Oct. 30, 2009
- Tree Boss: Trees Growing Close to Foundations; Sandy Feather; 2008
- ACES.edu: Tree Roots ... Where Do They Go?; Nov. 8, 2008
- ABC.net.au.: Tree Root Damage Factsheet; March 11, 2000