How Bentonite Clay Affects Your Home’s Foundation
Nature can be unforgiving—especially to your home’s foundation. If you’ve noticed signs like wall cracks, uneven floors, or stuck windows, the cause might be hidden beneath your home: the soil.
In Colorado, foundation problems are often caused by bentonite clay, a unique soil that behaves differently depending on weather conditions. In this guide, we’ll explore what bentonite clay is, why it causes foundation damage, and what you can do to prevent or repair it.
What Is Bentonite Clay Soil?
Bentonite clay is a highly expansive soil found across much of Colorado. While other soil types—like silt, loam, and especially sand within Denver city limits—are also present, bentonite clay dominates the landscape in many regions and poses the greatest risk to home foundations.
This soil is rich in montmorillonite, a clay mineral formed from weathered volcanic ash. What makes bentonite unique is its fine particle composition and remarkable ability to absorb and retain water. When saturated by rain or snowmelt, it swells dramatically. During dry spells, it shrinks just as drastically—creating cycles of movement that can compromise the structural integrity of your home.
Colorado’s weather only amplifies this effect. Most areas receive more than 60 inches of snow each year, but just around 15 inches of rainfall. With long periods of dryness and frequent droughts, the soil experiences constant moisture fluctuation, making it highly unstable beneath your foundation.
In the next section, we’ll take a closer look at how these weather patterns—and the soil’s response—can directly affect your home.
How Weather Effects Bentonite Clay Soil
As you can see, bentonite clay soil can cause many issues. Considering fluctuations in moisture levels, let’s explore exactly how this soil impacts your home and its foundation.
Wet Conditions: Swelling Soil and Hydrostatic Pressure
When spring snowmelt or heavy rains saturate bentonite clay, it absorbs water and expands with enormous force. As the soil pushes outward, it places intense hydrostatic pressure on your foundation walls.
The 3D rendering illustrates how hydrostatic pressure builds up and leads to foundation damage such as:
- Bowing basement walls
- Cracked concrete slabs
- Heaving floors
- Water intrusion
While bentonite does compact better than other types of soil, it’s still vulnerable. Even slight inconsistencies in the soil can let water in, and hydrostatic pressure will damage the very foundation the soil was supposed to protect.
Dry Conditions: Shrinking and Cracking
Colorado is known for its arid climate and frequent droughts. In extended dry periods, bentonite soil loses moisture, then shrinks and cracks, leaving gaps beneath your home. Without solid support, your foundation begins to settle, tilt, or sink. This back-and-forth cycle of swelling and shrinking is what makes bentonite clay so destructive over time.
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:
- Wall cracks
- Bowing walls
- Floor cracks
- Heaving slab floor
- Uneven floors
- Floor and wall gaps
- Drywall cracks or nail pops
- Sticking doors and windows
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 Beams – Specialized 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.
Stay Aware, Call Groundworks
Colorado’s natural beauty comes with hidden risks. Bentonite clay is part of the landscape—and with it, the potential for serious foundation problems. The best defense is early action.
If you notice any suspicious signs, contact us today to schedule your free inspection and repair estimate. Groundworks has more than two decades of experience helping Colorado homeowners navigate the challenges of expansive soils like bentonite. Whether your home is in Denver, Colorado Springs, or Grand Junction, our local crews understand the soil conditions and how to fix them.
Bentonite Clay FAQs
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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