February 20, 2005Basement Waterproofing - Inside - Part OneNow that you've covered the basics of basement waterproofing outside your house, it's time to turn your attention to the basement itself. While those first steps will keep a great deal of water away from the foundation under most conditions, the extremely high groundwater levels during times of intense and prolonged rainstorms present issues in many basement waterproofing projects. The effects of hydrostatic pressure--the force that pushes against your basement walls at any given point as a result of the weight of the water above it--should not be discounted. The higher the water table rises around your basement, the more hydrostatic pressure will be exerted against the concrete. The most common way to waterproof your basement under those conditions is to relieve that pressure, via a sump pump. Here's a little experiment you can try at home. All you'll need is a good sized mixing bowl and a disposable paper (or foam) cup. Take the mixing bowl and fill it with water, halfway to the top. Now, grasp the disposable cup by its rim, and holding it upright, place it in the middle of the bowl and press down until it hits the bottom of the bowl. As you push the cup downward, you'll feel the water pushing back. The pressure you feel is hydrostatic, in a sense. Let go of the cup and it will pop to the surface. A high water table works on a basement wall in a similar matter. Of course, the concrete basement wall is too heavy for the water to pop it out of the ground. But that water wants to find its way in, any way it can. So far, the cup has represented an impervious basement, sealed against the elements. We're about to change that. Take a pen or pencil and carefully poke a few holes in the side of your disposable cup. (They don't have to be big holes.) Now, try holding the cup at the bottom of the water filled bowl again. As the water starts to stream into the cup, you'll notice how it becomes easier and easier to hold it at the bottom of the bowl. Once the water level has equalized between the cup and the bowl, the cup will sit their happily ... you now have the equivalent of a basement full of water. Water seeks a level. It pushes against your basement wall in the hope of getting inside. Once it finds a way inside, watch out. The worst basement flooding I've experienced took place during Hurricane Floyd. The water first started seeping in through tiny cracks between the basement walls and floor. As the rain continued to fall, the sump pump was overwhelmed and water flowed freely from the sump hole into the basement. As the ground water level rose, the intense hydrostatic pressure popped holes in the basement walls. Water streamed into the basement from those holes as if propelled by by hoses. As this was happening, I scurried around the basement, plugging those leaks on the fly with hydraulic cement (which amazingly enough, will cure both underwater and under pressure). Through it all, thankfully, our electric service never failed. The sump pump continued to operate and I was able to drop auxiliary pumps into the basement to help with the process of draining. All in all, the basement hit a high mark of three feet, as a result of the storm. I quickly learned that an adequate sump pump system is one of the most important aspects of a successfully waterproofed basement.
|
