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Companies like AquaGuard Waterproofing Corporation that sell indoor perimeter drainage systems may use the concept of a clay bowl effect when trying to convince you to buy their services. Where is the Science? What is this clay bowl effect? AquaGuard Waterproofing Corporation sales representative drew the picture above when “explaining” the source of water seepage in my basement. I bought this concept and that was my mistake as the real source of the waterseepage was simply the surface water sliding along the foundation through cracks between the walks around the house and the exterior foundation. In other words, even if they hadn’t totally messed up the perimeter drainage installation itself, it was the wrong answer to the water seepage problems in my basement. Again, I bought it so my bad.
Note that it isn’t simply a matter of whether the soil around the foundation is more porous than the undisturbed soil. The real question is how does the water reach the basement walls from the outside? If the water from the surface can be directed away from the foundation by a substantial distance, say 10 to 15 feet, then it will have little opportunity to flow toward the foundation. The first line of defense against surface water is proper drainage away from the foundation.
This was certainly the case for my house, though the AquaGuard Waterproofing Corporation sales representative dismissed that source out of hand. His explanation was the following. It wasn’t a surface water problem at all! The real problem, according to him, was the ground water flowing from around the yard would pool into the clay bowl and seep into the basement where the walls joined the floor. When I told him that I usually saw the water entering from the walls and then flowing to the floor, he stated that was due to the rising water in the clay bowl finding its way into the cracks several feet above the floor. At the time I gave it no particular thought, he was the so-called “Senior Inspector” for AquaGuard. Only later did I realize that his explanation was suspect and quite possibly self-serving. Any difference in the height of the water and the Clay Bowl and the surrounding soil will tend to push the water to whichever side is lower. Of course since there isn’t any significant amount of water in the basement (one would hope) the hydrostatic pressure from the outside will force the water against the wall and, if cracks are present, into the basement. The question is simply this: Is there really a significant level of water building up in the so-called Clay Bowl at all? Or is the water penetrating the soil also simply flowing along the basement wall and finding its way into the house?
I indicated above that in the case of my house the Clay Bowl Effect explanation was suspect. How do I know this? Because after I had the trench path opened up I got to observe what happened when a very heavy rainfall occurred. We received over 5 inches of rain from the remnants of tropical storm Sandy but the basement remained dry. More importantly the trench path was dry. The ground water effect was bogus. Under normal circumstances the water would have flowed along the surface, down (not up) the walls and penetrating wherever it found a crack. Fortunately the contractor I had come in and remove the tar not only patch the numerous cracks in the foundation (the real entry point for the water) but they also did an excellent job caulking the walks along side the foundation. This is a temporary patch, as I still need to grade the surface so water flows away, but it was a great demonstration that the real problem wasn’t what AquaGuard sold me at all.
But I digress.
I want to dedicate this post to exploring where this concept came from and what validity it has, if any. If you search on-line you’ll find waterproofing companies explaining seepage using the “science” of the Clay Bowl Effect. Really? I’ve yet to find an actual scientific article on this, but I’ll keep looking. More to follow!