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Popular Methods of Basement Waterproofing


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Waterproofing for basements has become very trendy as homeowners have sought to convert rough basement space into living space. Techniques and strategies for waterproofing can be categorized into two major categories: Internal and External. We will explore popular methods and techniques of waterproofing basement walls externally in this article.

Why should you waterproof your basement walls externally?

Internal waterproofing is more popular and cheaper, isn’t it? On a general scale, yes. The Internal methods are very common and many of them are not expensive. Nevertheless, to be frank, internal basement waterproofing is not really waterproofing at all because water is not prevented from entering the basement walls. Instead, the method only deals with the water that has entered. But when you do your waterproof externally, you actual prevent water from entering them in the first instance. This is crucial because water is a natural destructive agent to building materials. With time, continuous water exposure breaks down the composition of any material even the mortar and block of which are the major building materials for most foundation walls.

So what can you do to the outside of your basement walls? There are two strategies in exterior basement waterproofing: drainage and barriers. A third strategy called diversion which can be thought of as an adjunct to drainage, also exists. When you install systems to drain water from the ground surrounding the basement, you are using drainage. In drainage, you’re giving the water an easier path to follow than to enter your foundation walls considering that water follows the path of least resistance.

The rain gutters and downspouts on your house constitute the diversion systems. The function of these systems is to divert that rain water away from the ground surrounding the foundation and therefore remove any undue burden on the drainage system. Barrier systems involve the application of a waterproof coating on the external surface of your foundation walls. When this is done, the small amount of ground moisture in contact with your basement walls will still not get in because it won’t be able to penetrate the waterproof barrier. All of the products, devices, and techniques that are available for external basement waterproofing are in one of these three categories. Nevertheless, they are all more effective if used with one another.

Commonalities Between Barrier and Drainage Methods

Substantial excavation around the structure is required for both to expose the basement walls. This excavation represents the majority of the expense of exterior waterproofing and can be the main reason behind the decision for interior solutions by most homeowners. Excavation is expensive, disruptive and risky. Your foundation walls can be damaged with an excavator by an inexperienced operator. Shifts in your foundation walls can result from excessive excavation at any a point.

Lastly, there’s always a likelihood that excavation can damage an underground utility line that was either incorrectly marked or that was not known. All of these possibilities can contribute substantially to the project cost. The benefits may still make external waterproofing a worthwhile venture, despite the risks and costs associated with it.

Exterior drainage systems are usually called footer drains or tile drains. A channel that is dug around the perimeter of the foundation walls at a depth just below the wall footer is the major component of this system. The channel is filled with gravel, in other words, an aggregate. A pipe is laid in the middle of the aggregate. There are perforations on the pipe that permit liquid water to enter into it. As ground water descends it finds little or no resistance to entering the trench as there is abundance of air spaces within the gravel (aggregate). The water easily enters the pipe through the perforations once in the trench. The pipe then leads to a remote drainage location like a storm drain or a natural ground water drainage path.

A good exterior footer drain system benefits tremendously from a good diversion system. Just like we earlier said, the rain gutters and spouts on a building makes up the diversion system. Why do I need to worry about the rain water when I have an underground system draining water away from my house? You may wonder. You should worry about the rain water because it carries silt and other particulate matter dissolved within it. That sediment builds up within the footer drains and begins to obstruct the flow of water with time. If more water flows into the footer drains, the sediments will accumulate faster. Most rain water will be kept out of the drainage system by a good diversion system. This is carried out by gutters collecting water from the roof edges and downspouts emptying at least 5 feet away from the foundation walls onto ground sloping away from the house. In an ideal scenario, the downspouts will drain into underground pipes emptying into storm drains. If more rain water is diverted away from the footer drainage system, the system will last longer.

Lastly, waterproof layers applied to the outside surface of the foundation walls make up the barrier systems. Any residue of soil is removed to get a clean application, once the ground is excavated to expose the wall surfaces. The barrier material, which is often referred to as a sealant, is usually based on rubber or a polymer. Some products are actually a cement or asphalt and applied as such. The latest commercially available products are quite versatile. They can be applied with sprayers because they are thin enough, and this greatly reduces the labor required and they are still durable enough and strong enough that once fully cured many are warranted to last 10 years or more when properly used.

External diversion, drainage and barrier systems working together are remarkably effective at waterproofing basement walls. While external systems can be costly and most are installed during building construction, a well designed system installed at any point in a building’s life cycle can give comfortable, water-free basement living for several years.


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