Why Do Trees Cause Concrete to Crack? (How to Prevent it)


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Have you ever thought that an aesthetically grown tree at your front door or in the backyard can cause big trouble for you? It can give you never-ending problems and crack the walls of your house.

When the tree roots absorbs water, the soil moisture level is lowered, resulting in shrinkage. This shrinkage causes movement of underground soil, and the concrete foundation is disturbed. The same happens when water is lost during transpiration; pressure develops under the concrete and causes it to crack.

If your house or any building is suffering from root damage, you are at the right place to find all the causal factors. 

Some effort has to be made to prevent serious damage to concrete structures. Here you will get the core reasons for cracks and the preventive measures to deal with this situation. 

Most importantly, you will also find the answers to some of the underlying issues caused by roots. So, what are you waiting for? Let’s dig in!

Why trees cause concrete to crack

Why do trees cause concrete to crack? 

The roots’ trees are the main culprits of cracks in concrete and result in significant structural problems.

Tress roots tend to grow in search of water and nutrients. This is why we often find where there are cracks in a house foundation, there are also some type of water line which has developed a small leak.

Additionally, when we talk about damaging the trees’ roots, we cannot neglect the soil in which the plant is growing. 

Both are equally responsible for the cracks.

Most soils are expansive and can become loose while absorbing significant amounts of water. When soil absorbs water, the volume of the soil is increased, and it expands. 

This expansion causes pressure to the building and results in the movement of the building. 

Similarly, when soil releases water, it shrinks and again results in a crack to the concrete structure due to stress. 

The damage may be minor or significant and depends on the 

  • Extent of root movement
  • Amount of soil movement

That is why, when you are building your house or growing trees closeby, make sure you have an idea about the soil to prevent future problems. 

Roots in search of water

As you know, plants need water to grow which they absorb from the roots.

When you water the plant, it penetrates into the soil where it becomes available for the roots. 

Plants and trees search for water by allowing their roots to grow outwards and also downwards into the soil. 

As roots absorb water from the soil, the soil’s  moisture content decreases. This causes it to shrink and move downwards, which is known as subsidence.

This generally happens with clayey soil. If you are making a new house or establishing a garden, make sure you know what type of soil sits in the base.  

Transpiration

Transpiration

Transpiration is the loss of water from leaves that the plant absorbs through roots. The water travels from roots to stem and then the leaves, where it exits to the atmosphere. 

When the water is lost from the leaf of the plant, the roots will absorb moisture from the soil which causes the surrounding area to shrink. 

This shrinkage disturbs your house and concrete cracks. Whether it is sidewalks, driveways, or patio walls, small cracks will keep spreading and enlarge. 

Strength of the Foundation vs the Pressure from the Roots   

Concrete side walls and driveways are made with rebars embedded within the concrete to help it flex without breaking. 

The forces that are placed on these structures by subsiding soil or growing roots are so great that they can cause even a 6 inch thick reinforced driveway to crack. 

The additional weight of cars and other machinery on driveways can add to the breaking force required to crack the concrete. 

To get a grasp on the forces that cause concrete to crack we will have to discuss the concept of strength.

Compressive strength is the strength of building material to bear the super high weight. 

But when it comes to tensile strength, that is, the amount of stress a material can withstand without breaking. 

When roots put pressure, they create tension on the foundation.

From the definition of tensile strength, if the concrete tensile strength is weak, it will cause cracks in the foundation.

plant growing through cracks in concrete

How to Prevent Tree Roots from Damaging Concrete?

If your house or surrounding structure is getting damaged and you are worried about safeguarding, there are several steps you can take to make your place safe. 

These are all workable and give ease of sustaining your property.

Install a root barrier

The first thing you can do to prevent tree roots from breaking in concrete is to install root barriers. 

This is the most effective way that you can use when paving your sidewalk or foundation. 

If you want to do it in an established house, dig the ground deep and install a root barrier. 

Metal barriers are best and long-lasting so, if you’re going to get rid of this problem for a longer period, invest in barriers. 

Remove invasively growing roots

If the roots are grown invasively, cut them and remove them from the damaging section of your house or driveway. 

It would be best if you did this when new roots are developed.

A more effective way in controlling unruly roots is to just remove or cut down the tree that’s causing the problem in the first place. 

Grow slow-growing plants

When gardening is your passion, plan it properly and grow plants that are favorable to your place. 

You can plant slow-growing trees with a less aggressive root system to deal with this situation.

There are some slow-growing trees that you can plant in front of your house. 

  • Japanese snowball
  • Magnolia
  • Japanese red maple
  • Chinese fringe tree
  • Juniper
  • Cherry laurel

Make a Deep Foundation

When designing your house, make a deep foundation to prevent root damage.

You can also make full basements to add more strength to the building. 

The older homes with shallow basements are more vulnerable to destruction from roots than newly designed houses with full basement.

Can I Cut a Tree Root Without Killing the Tree?

You can cut and eliminate damaging roots without killing the tree, especially if it is not very young. 

If you are working on an established tree, make sure you are pruning roots more than 2 inches wide. Do not remove roots that are very close to the trunk as it can make the plant unstable and unhealthy. 

Herbicides are an excellent option to remove the roots of a tree, but you have to be very careful when using these chemicals. 

As plants live in combinations and there are chances of chemical transfer from one plant to the other. So, if you are using any herbicide, do not forget to go through the instructions. 

Also, only use chemicals on trees that are far apart from other plants.

The second option is to cut the roots manually. You need to be very conscious when cutting and never remove roots more than twenty percent of above-ground tree roots. 

Steps to Cut a Tree Root without Killing the Tree

  • First, clear the surface with the spade and remove the soil around the tree. 
  • Trace the roots and remove them underneath the soil. 
  • Now measure the tree’s diameter as you need to cut roots that are 3-5 times the diameter of the tree. Like if your tree’s diameter is 4 feet, locate roots that are 12 feet apart from the tree. 
  • Mark the surface and dig in the soil to expose the roots. 
  • Use a saw to cut roots and carefully pull the roots up.
     
  • After cutting, cover the hole with soil and make sure there is no surface left without soil.
weeds growing through cracks in concrete

Can an Existing Crack get Bigger if Weeds Grow in them? 

Weeds can grow wherever there is an opening in the concrete. Additionally, if the tree roots have cracked the concrete, there are chances that it will get bigger if weeds grow in them. 

These invasively growing weeds do not need care and may extend to damage the building. 

They can easily be removed using home remedies, pull out with your hands or use commercially available weed killers. 

Once the weeds have been removed you would then have to seal the crack to prevent further weed growth in the future.

Knowing What Trees to Plant

One of the best approaches is to research and plan. 

When you grow a plant and turn it into a tree after years, you don’t expect the roots to be causing any damage to your home.

Which is why you should plan things and grow what suits your soil, climate, and need. 

Many plants grow at a slow rate, have tall growth, and do not make complex root systems. 

Go with the best suitable trees and avoid trees that grow invasively. 

Here is a list of trees that you can grow at your place without worrying about the potential root damage.

  • Oaks
  • Poplars
  • Ash
  • Norway maple
  • Tulip tree
  • Silver maple
  • Black locust
  • Sweetgum
  • Sycamore
  • Boxelder

If your property is damaged with the roots, work with preventive tips and make your place safe.

If you want to remove roots permanently, you can also do that but bear in mind respect nature before doing anything.

JayLea

JayLea has a passion for plants and has been gardening since 2015. He has valuable knowledge about gardening and houseplant care and can answer everyday practical questions that every plant owner has.

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