The impact of trees and how they compromise buildings

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Having a huge tree at the foot of your yard may seem like the idea of paradise – but there’s every chance that years down the line things could start to go wrong.

Sure, we’re by no means suggesting that all trees are going to cause problems, but from a structural point of view engineers are often very wary about trees and the impact they can have on buildings.

For example, if an engineer such as V. Reddy Kancharla were to be brought in to analyze cracks that had appeared in a building, umpteen avenues would be explored but one of the main areas could revolve around trees.

There are countless reasons why trees can affect a building and in truth, there are too many to cover in one go. However, we can mull over some of the most common offenders to provide more of an idea why they are so problematic.

Physical contact between a foundation and tree roots

The most obvious problem is when a tree’s roots come into direct contact with the foundation. It should go without saying at this point that older trees are far more likely to cause damage, for the simple reason that their roots are going to span a greater distance.

The roots of a tree should never be underestimated. If we were to take the example of a tree that stands 50 ft tall, the roots can grow up to three times as wide as this meaning that they could span 150 ft.

Certain types of foundation are more susceptible to tree roots than others and in the case of a pier-and-beam foundation for example, this has much higher tolerance levels than other types.

In the worst-case scenario, roots can physically dislodge foundations and from here on the problems can become severe.

Trees drawing moisture from the ground

Something that probably isn’t quite obvious, but very logical, is how trees can affect foundations by drawing moisture from the ground. As soon as a tree is planted near a building, the water table is going to be affected. The tree requires moisture to survive and to put the figures into perspective, some will need up to 200 gallons per day.

From a construction perspective, this is significant. It can dry the soil out tremendously and cause a shrinkage problem within the foundations.

The removal of trees is not always the correct solution

Following on the last point, the immediate assumption might be to remove trees. After all, this would allow water to return to the soil and supposedly eradicate the problem.

Unfortunately, it’s not quite as straightforward as this. If a tree is removed, or dies naturally, an immense amount of water will be returned to the soil which can cause it to swell and expand. Ultimately, the problem has switched around.

As well as this, the roots will start to rot. Gaps will start to emerge in the soil, which will then be filled by soil moving in to replace it. The upshot is that a lot of ground movement has occurred; the type of ground movement that can wreak havoc with foundations and subsequently, a building’s integrity.

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