Ask anyone what they think about waterproofing a basement and they will have an idea or opinion about how it should be done. Ask a person who has experienced a basement leak in their own home and they will have a very definite idea of how to solve basement leaking. The truth lies in the fact that not many people understand how to waterproof a basement unless they have years of experience doing it.

Dig It Out

The most common belief of how to waterproof a basement is that it is done from the outside. That you dig out the earth around the sides of the foundation wall and ‘seal’ the wall somehow whether it be with plastic sheeting, tar, or other membrane. The fundamental problem with this approach is that the basement also has a floor and you cannot dig under the floor. It is also the space under the floor that builds up the most water pressure and tends to be the greatest source of leaks. The biggest problem though with this concept is that there really isn’t anything that you can use to seal porous and underground concrete. Any vapor barriers have to have some sort of seams for water to go around and they cannot run underneath the house i.e. the most terminate at the bottom of the wall and so water can simply rise up between the barrier and the wall. Tar also is useless after a few seasons because after it has gotten wet and dry, hot and cold it becomes brittle and cracks along the bottom of the wall where the footer and foundation wall meet. This is also the spot the where most water enters.

Painting

Another common idea is that you can paint the walls with a waterproof paint that will stop any leaks. This is simply impossible. Water is one of the smallest molecules on earth. Paint is one of the largest. Any paint, no matter how it is made, will peel if water is applied from beneath the substrate it is attached to. Paint actually does more harm than good as it prevents the real condition of the wall from being apparent for many months until there is a bigger problem with mold or crumbling mortar.

Yard Slope

It is another very common misconception that it is the slope of the yard that is causing the basement to leak. That the slope of the ground is leading water to the basement and so the solution is to slope the ground away from the house. This concept would be entirely true if the basement floor were only 1 foot under ground, but most basement floors are 6,7 or more feet under ground and it is the water much deeper underground that is causing the problem, not the little bit of water apparent on the surface. In a heavy rain there is much more water in the ground than there is on the surface, the dirt is very absorbent. The real problem here is the fact that although there is water accumulating outside the foundation wall there is nothing to prevent the water from penetrating the wall and flooding the basement. Basements are deep in the ground and waterproofing them often requires more than one solution.

The most foolproof solution is to install a sub-floor drainage system that also drains the wall. This sub-floor system then drains to a sump pump well where the water is collected and expelled. There are many different varieties and designs of such systems each with their own twists, but a good one should have a lifetime warranty on both the pump, the system and the install.