Basement waterproofing has become increasingly popular as homeowners have sought to turn basement space into living space. Waterproofing techniques and strategies can be grouped into two main categories: external and internal. In this article, we’ll explore popular external basement wall waterproofing methods and techniques.
Why waterproof your basement walls externally? Isn’t it true that internal basement waterproofing is more popular and cheaper? Well, in general, yes. Internal methods are very popular, and many of them can be extremely affordable. However, strictly speaking, internal basement waterproofing is not really waterproofing because it does not prevent water from entering the basement walls. Rather, you are devising methods to deal with the water once it enters. On the other hand, when you waterproof your basement walls externally, you are actually preventing water from entering them in the first place. This is important because water is naturally destructive to building materials. Over time, constant exposure to water breaks down the composition of any material, even the mortar and block from which most foundation walls are built.
So what can you do on the outside of your basement walls? Well, exterior basement waterproofing really comes down to two types of strategies: drainage and barriers. There is also a third strategy known as diversion that can be considered a complement to drainage. Drainage means that you are installing systems to drain water from the ground surrounding the basement. Considering that water is following the path of least resistance, you are giving the water an easier path to follow than entering its foundation walls. Diversion systems refer to the gutters and rain downspouts in your home. These systems are designed to divert rainwater from the ground surrounding the foundation and therefore do not place undue burden on the drainage system. Barrier systems involve applying an impermeable coating to the exterior surface of your foundation walls. In this way, the small amount of soil moisture in contact with the basement walls will not yet enter because it cannot penetrate the waterproof barrier. All products, devices and techniques available for waterproofing external basements fall into one of these three categories. In addition, they are all more effective when used together.
Both barrier and drainage methods have something in common. Both require substantial excavation around the structure to expose the basement walls. This excavation accounts for most of the cost of exterior waterproofing and is probably the main reason most homeowners opt for interior solutions. Digging is not only expensive, but also disruptive and risky. An inexperienced operator can damage your foundation walls with an excavator. Excessive excavation at any point can cause changes to your foundation walls. Lastly, there is always the possibility that excavation could damage an underground utility line that was incorrectly marked or is simply not known. All these possibilities can substantially increase the cost of the project. Despite the risks and costs associated with external waterproofing, the benefits can still make it worthwhile.
Exterior drainage systems are generally known as standing drains or tile drains. These systems consist of a channel that is dug around the perimeter of the foundation walls to a depth just below the foot of the wall. The channel is filled with an aggregate, that is, gravel. In the middle of the aggregate there is a pipe. The pipe has perforations that allow the entry of liquid water. As the groundwater descends, it encounters little or no resistance to entering the trench due to the abundance of air spaces within the gravel (aggregate). Once in the trench, the water also easily enters the pipe through the perforations. The pipe then leads to a remote drainage location, such as a storm drain or natural groundwater drainage path.
A good outside footer drainage system benefits greatly from a good diversion system. As we mentioned earlier, a diversion system is made up of the gutters and rain pipes in a building. You may be wondering why you should worry about rainwater when you have an underground system that drains water from your home. The reason is that water carries silt and other dissolved particles within it.