How To Look At A House
McGarry and Madsen's home inspection blog for buyers of
site-built, mobile/manfuactured and modular homes
How can trees damage a house?
Friday, August 31, 2018
The right types of trees strategically placed around a home provide numerous benefits beyond just shade and curb appeal. They hold the soil in place on a sloping site, provide a windbreak, and a habitat for birds and other backyard wildlife. Plus, some varieties provide flowers or fruit.
But the wrong species of tree, or the right tree in the wrong location can cause minor to catastrophic damage to a home. Here’s some of the ways that trees can be detrimental:
•• Dead, diseased, or structurally defective trees can fall on the house. The tree in the photo above was sheared by lightning and, while still alive, will eventually topple. That cute tree hollow that’s home to the elves in cookie commercials is actually a structural defect that warrants removal of a tree.
•• Branches overhanging the roof can fall, causing anything from a minor puncture to major structural damage. Also, leaves falling on a low-slope or flat roof can accumulate into a mat that blocks roof drainage and becomes acidic as it rots, which both stains and deteriorates the roof surface.
•• Leaves and small branches can clog gutters, causing water backup onto roof overhang areas and, in northern climates, ice dams.
•• Tree branches growing directly over the surface of the roof sway back and forth in the wind and scrape away the the surface of shingles. If the home has a septic system, roots of trees nearby will follow the outflow of water backwards into the drainfield and, eventually, into the septic tank, clogging the system.
•• Trees close enough to a house that their roots can grow under the foundation, floor slab, porch, or patio may damage the structure. While large roots of some species can cause uplift, like in the photo below, it is more common that the leeching of water from under the structure by a maze of thirsty roots will cause settlement over time.
Removal of the all the lateral roots near the surface of the soil on one side of a tree—during the construction of a new in-ground pool, for example—will weaken the tree’s resistance to lateral wind loads and cause it to fall in a storm. Also, trees that lean more than 15-degrees out of vertical may be dangerous, especially if they were originally growing vertically or there is uplifted soil on one side. Some species of trees that become unbalanced will develop a callous-like growth at the base on the weakened side called “reaction wood,” which is one way that a knowledgeable tree surgeon will recognize a problem.
“You know, Gainesville is rated as one of the top ten cities for trees in U.S.,” says Robin Hargis, a certified arborist with Sky Frog Tree Service. “When I first moved here I thought I’d died and gone to heaven. But all those wonderful trees require maintenance.” It’s a good idea to look over all your trees periodically for any potential hazards, and large, older trees should be examined carefully from top to bottom. Robin also recommends having a professional arborist inspect the trees on your property on a regular basis and whenever you notice an sign of a potential problem.
If you suspect a problem, call a tree surgeon that is registered as a Certified Master Arborist with the ISA (International Association of Arboriculture)—which means that he or she has passed testing and is well-educated in tree growth, diseases, and proper pruning techniques.
Also, see our blog post Which trees are most likely to fall over on your house in a hurricane?
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