Waterproof Expert

Waterproofing tips & tricks


How long does bentonite waterproofing last?

Bentonite waterproofing can last the lifetime of your building. Bentonite clay itself has a lifespan of hundreds of years. It expands at it absorbs moisture forming a watertight barrier that becomes so dense water cannot seep through. Bentonite can self-repair and supports repeated cycles of wetting and drying without losing its waterproofing characteristics.

How does bentonite waterproofing work?

Bentonite clay is made of sodium bentonite. This material has a high capacity to absorb moisture. It also expands in the process. It can swell to roughly 15 times its volume while in a dry state.

The more moisture it sucks up, the more it expands. The more it expands, the denser it becomes. After reaching its maximum water absorption capacity, bentonite clay will have become so dense that water cannot seep through.

Bentonite clay mixes with the soil and forms a solid membrane that blocks moisture from penetrating the foundation walls. In this manner, water is stopped before it reaches the building itself.

Soil tends to absorb and retain moisture. If you don’t waterproof the foundation of your building, moisture will gradually penetrate through the cracks of the walls and eventually reach your basement.

To prevent that from happening, you need to waterproof your foundation and basement. Bentonite waterproofing is one of the most reliable and cheap methods to get the job done. The average bentonite price is $85 per ton, and a bentonite sheet typically costs $5-10 per square foot.

How do you seal a foundation with bentonite?

There are several methods to seal a foundation using bentonite. Each method comes with its own set of advantages and disadvantages. Consult with your professional waterproofing contractor on the best method to use in your case.

One common method consists of injecting bentonite into the soil. A rod is inserted along the building’s exterior foundation. Then, a low-pressure pump pumps bentonite clay through the rod. The bentonite clay sets up after 45-60 minutes depending on its consistency. The clay continues to expand for 30-35 days forming a watertight membrane that protects the building against water damage.

Another method is to excavate the soil around the foundation to expose the foundation walls. Bentonite is then packed into the space between the foundation walls and the soil. Sometimes, a layer of bentonite is placed between two sheets of geotextile fabric to better keep it in place and prevent it from migrating.

If you live in a low-lying area or the water table is high, you should also use an additional form of waterproofing to make sure your foundation is well protected against water damage.

Always hire a professional waterproofing contractor for such tasks. They are professionally trained, and use the highest quality materials and technologies.


Bentonite clay has a life span of hundreds of years which means that bentonite waterproofing can last the lifetime of your building. Bentonite clay expands as it absorbs moisture. After reaching its maximum water absorption capacity, it forms an impermeable barrier that prevents moisture from reaching the foundation walls.


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