How Water Can Permeate a Concrete Foundation over Time
Is water seeping through your concrete foundation? If left untreated, water can slowly erode your foundation and lead to costly foundation repairs. Here in Toronto, we respond to several hundred basement waterproofing calls a year. Some repairs are minor, while others are costly repairs. Most of the costly foundation repairs we treat could have been prevented, or at least minimized, if proper measures had been taken earlier.
One of the foundation problems we frequently come across is a slowly eroding foundation due to a prolonged period of water penetration.
Nature often has its way with buildings, no matter the constructors’ intentions. Sometimes builders don’t try hard at all. Perhaps they are running short on time or materials. Possibly, they don’t understand the theory behind what they are doing. Property owners end up with the result, long after the construction team is gone.
In this article, we examine the phenomenon of wet concrete foundations. What causes them, why they happen in some places and not in others, what to do about the problem, and so on.
The Inherent Weakness of Concrete
Concrete consists of five essential ingredients:
- The first is stone chip that adds bulk and strength.
- The second is the steel bars that prevent the mix from cracking.
- The others are cement mixed with sand to form a “glue” that holds the thing together when water’s added.
Concrete is porous when it’s dry. When there’s water in the area, it sucks it up like a giant wick.
Where Does the Water Comes From?
Dig a hole that’s deep enough, and it starts to fill with water like a drinking well. That’s because there’s always water somewhere beneath the ground. The only uncertainty is the depth. It could come from rainwater that’s filtered down, from an underground stream, from a leaking water pipe, or from a leach drain.
The same gravity that prevents us from flying off the earth presses down upon the ground, compressing it. This force pressurizes the moisture just like when a child squeezes the trigger on a toy water gun. Scientists call the energy that results hydrostatic pressure. This turns ground water into a mighty powerful thing that can find a way through most materials.
Concrete is a Natural Target
We mentioned earlier that dry concrete acts like a natural wick. As the water pooled on top evaporates, it siphons up more to replace it. This is why vacuuming it away seldom helps. Sometimes the concrete cracks due to poor construction methods, ground movement, or a weak mixture of the “glue”. When this happens, groundwater comes bubbling up through a fissure.
How to Prevent This From Happening
As we said earlier, nature will have its way. If you must build in damp earth, you can try to divert the water by installing French drains, and putting down a moisture barrier before you cast the slab. This is by no means as simple a matter as it may sound. Water is a dynamic thing and incredibly persistent.
What to Do if This Fails
Over time, the water permeating through your concrete floor is going to soften and dilute the glue, eventually causing it to begin to disintegrate. There are two strategies to counter this.
- The preferred one is to install French drains that lead the groundwater elsewhere.
- Second prize is to try to stop the siphon process by applying a waterproofing medium on top.
More often than not, you need a combination of the two to achieve success.
