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How Bentonite Clay Affects Your Home’s Foundation

Nature and the elements can be brutal, especially to your home. 

Upon spotting damage like wall cracks and uneven floors, it’s natural to wonder how they happened. The answer is complex, yet simple, and lies beneath your home – the soil. 

Your home relies on its foundation for stability, and the foundation depends on the underlying soil for strength. When the soil is unstable – affected by abundant or lacking moisture – the foundation suffers. 

In Colorado, most homeowners are familiar with foundation damage caused by soil, in particular, bentonite clay soil. 

In this article, we’ll delve into bentonite clay soil, how it impacts foundations, and how to repair foundation damage. 


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What Is Bentonite Clay Soil?

Bentonite clay is an expansive soil found throughout much of Colorado. Other types are present – such as silt, loam, or more commonly sand in the Denver city limits – but bentonite clay has a dominant hold in the ground. 

This soil is composed of montmorillonite, a clay mineral that is formed from weathering volcanic ash. 

It is largely made up of small particles and has the ability to absorb and hold large amounts of water, making it highly expansive. That means it swells when exposed to excessive rain or snowmelt and shrinks when dry. 

The weather has a significant impact on the soil’s condition. 

Many locations throughout Colorado typically receive more than 60 inches of annual snowfall, but only about 15 inches of annual rainfall. 

Most residents are familiar with Colorado’s arid, dry nature, as well as frequent droughts

Next, we’ll further explore how weather and soil interact to impact your home. 

Effects of Bentonite Clay Soil on Home Foundations

As you can see, bentonite clay soil is quite problematic. Considering fluctuations in moisture levels, let’s explore exactly how this soil impacts your home and its foundation. 

Shrinking and Unstable When Dry

More often than not, Colorado experiences periods of drought. 

When the bentonite clay soil lacks moisture, it dries up. As this happens, the particles separate and become less dense. 

The soil then shrinks and begins to settle beneath your home, leaving the foundation without proper support. Your foundation will follow suit and begin to settle into the earth as it seeks stability. 

Additionally, the soil surrounding your basement or crawl space walls can recede. 

Expanding and Unstable When Wet

Even with above-average winter snow, Colorado stays generally dry. When the snow melts or the rain does come, usually in the spring, it saturates the soil. 

Because of its near-constant state of dryness, bentonite clay soil cannot handle all this water. As the soil absorbs the water, it expands, and hydrostatic pressure builds. You can see more examples of hydrostatic pressure in this video

This force becomes so strong that as it pushes against your foundation, it leads to various damage like cracking, heaving floors, and bowing walls. 

Signs of Foundation Problems

We just mentioned a couple of symptoms, but here’s a comprehensive list of different foundation problem signs you’ll notice when unstable bentonite clay soil leads to home damage: 

Repairing and Protecting Your Home

Whether your home has suffered at the hands of unstable soil or you want to protect it from potential damage, there are several ways you can do so. 

Repair professionals like Groundworks can install the following solutions in your home. 

Proper Moisture Control

While leaks and flooding aren’t as common in Colorado, it’s a good idea to proactively waterproof your basement or crawl space

This includes installing interior basement or crawl space drains to capture leaking water, a sump pump to remove it from your home, and a dehumidifier to remove excess moisture. 

Foundation Repair Solutions

Pier systems like helical piers are used to bypass unstable bentonite clay soil and put your home back on solid ground. 

These piers, which feature a round helix blade, are installed deep into the ground and past the bentonite clay until they reach bedrock or more stable load bearing strata. 

Not only do these piers permanently stabilize your foundation, but they can potentially lift settling sections. 

Wall Repair Solutions

Various solutions can be installed to address basement walls that have begun to crack and bow inward. 

  • Carbon Fiber Straps – Low-profile carbon fiber straps can be placed on walls with minor cracking and less than two inches of movement. They reinforce the walls by holding them in their current positions. 
  • Wall BeamsSpecialized wall beams that attach to the basement floor and floor joists, which you can see here, push against hydrostatic pressure. They can be professionally tightened at intervals to try to improve the walls. 
  • Wall Anchors – Similarly, a wall anchor system can help brace and potentially correct bowing walls. Earth anchors are embedded in stable soil at least 10 feet away from walls. Steel rods connect these exterior anchors to interior plates in your basement. 

Educate Yourself So You Can Make the Best Decision for Your Home

Colorado’s geography is home to many wonders, including bentonite clay soil. While the earth itself can be breathtaking and bring amazing beauty, it also has a darker side: cracks in walls brought on by its power. 

Being prepared for any potential surprises from nature is key to protecting your home. Make sure you stay vigilant, so you’re ready to act when necessary. 

Groundworks wants to be your partner in foundation repair. Our team has been fixing foundations for more than 20 years. As homeowners ourselves, we know exactly how bentonite clay soil wreaks havoc on foundations, as well as how to fix the problem with tailor-made solutions. 

To learn more, contact us today to schedule your free inspection and repair estimate.

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Bentonite clay is a volatile soil type that contributes to various home damage, so its advantages are slim to none. 

However, what can be said about this soil is that most homeowners in Colorado are aware of its prevalence, as well as the potential issues they’ll have to deal with. It’s not a question of if the foundation will be damaged, but when.

Bentonite clay soil stands out due to its unique chemical makeup. It is composed of weathered volcanic ash and has an abundance of montmorillonite which is known for absorbing water and expanding to many times its original size. This makes bentonite clay highly expansive when exposed to moisture, compared to other clays with less montmorillonite. 

Foundation repair is only covered by your homeowner’s insurance policy if the damage is a result of a sudden or accidental peril.   

These include but are not limited to, tornados, lightning strikes, vandalism, or a vehicle crashing into your home.  

Speak to your insurance agent for a complete coverage overview.   

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Service Areas 

Groundworks is proud to serve communities throughout the United States, especially in Colorado where foundation damage is common because of bentonite clay soil. These areas include: 

  • Denver 
  • Boulder 
  • Fort Collins 
  • Littleton 
  • Colorado Springs 

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