Expensive and extensive. Installing a bentonite waterproofing system on an existing house usually calls for complete excavation of the foundation. Interior drain and sump pump systems are more affordable and also more effective.
Bentonite is a naturally occurring type of clay soil that has many uses. It is a primary ingredient in cat litter and in some pore-cleansing cosmetic products. Bentonite is also used by some contractors as a waterproof coating on basement foundations.
Bentonite waterproofing is an exterior waterproofing treatment that is supposed to work by forming a barrier between wet soil and the building foundation. Like any type of clay, bentonite absorbs moisture.
As water molecules bond to clay particles, the clay expands, filling cracks and gaps in the foundation so that water can’t get in.
Like any exterior waterproofing system, bentonite waterproofing is more effective and more affordable when applied during new construction. The clay is usually applied in thin sheets, but it can also be sprayed onto the foundation.
With an existing house, the foundation must be excavated in order to apply bentonite sheets. Alternatively, some contractors will inject liquid bentonite mud into the soil around the foundation.
Bentonite waterproofing goes by other names, like “hydroclay” “sodium bentonite“ and “granular bentonite.”
Before agreeing to have your foundation treated with bentonite, it’s important to know about certain
limitations and disadvantages. Here’s a quick rundown:
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