Bentonite is a naturally occurring clay that swells dramatically when it absorbs water, a property that makes it useful in construction as a waterproofing and sealing material for foundations, ponds, and various below-grade applications.
When bentonite panels or granules come into contact with moisture, they expand and form a dense, low-permeability barrier that resists further water movement through it.
What Is Bentonite Used For?
- Foundation waterproofing panels or sheets
- Sealing joints and penetrations below grade
- Pond and reservoir liners
- Grouting applications requiring a swelling seal
Why Is Bentonite Important?
Because bentonite’s swelling behavior creates a self-sealing barrier, it’s particularly valued for its ability to seal around irregular surfaces or minor construction imperfections that a rigid membrane might not conform to as effectively. This self-healing quality also means minor punctures or damage to a bentonite waterproofing system can sometimes seal themselves as the surrounding bentonite continues to swell into the gap.
Bentonite does have limits worth understanding, since it requires consistent moisture to maintain its swollen, sealed state, and repeated wetting and drying cycles can gradually reduce its long-term effectiveness compared to some synthetic membrane alternatives. Because it’s a naturally occurring material, bentonite is also often favored in projects where environmental considerations make synthetic membrane alternatives less desirable. Its natural origin and long history of use also give it a proven track record across many decades of below-grade construction. This track record continues to make it a trusted choice among waterproofing professionals. That reliability continues to earn it a place in modern practice. Its dependable performance keeps it in steady use today.
Bentonite vs. Foundation Waterproofing
Bentonite is one specific material used within a broader foundation waterproofing system. Foundation waterproofing is the overall goal and can be achieved with bentonite panels, liquid-applied membranes, sheet membranes, or other materials depending on site conditions and budget.