Leak in the basement? Before you replace weeping tile...

Posted by Luc Gerber on Thu, May 17, 2012 @ 07:39 AM

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If you are going to experience a leak in the basement it will typically happen after heavy rainfall or when there is a rapid snow melt in the spring. In most cases, these basement leaks are attributable to water penetrating the foundation due to hydrostatic pressure; however, this is not always the case.

In general, the average leak in your basement reveals itself as slow seepage of water onto the basement floor. However, not all basement leaks are the result of problems with your foundation, or problems with your weeping tile for that matter. Sometimes, water in the basement is actually a symptom of a rising water table beneath your basement floor. This particular cause of basement leaks is much easier to confirm in an unfinished basement that in a finished basement for the simple reason that visible staining on unfinished basement walls is easy to see while the staining is not visible behind finished basement walls (unless of course you cut the walls open).

Determining the cause of a basement leak

The image below is of a poured concrete foundation showing evidence of water staining several inches above the floor surface. In this particular instance, within the room, there was no visible evidence that water penetration had ever occurred through the foundation walls  (there were several foundation cracks that weren't leaking). Furthermore, the homeowner reported that the basement had flooded to such an extent that there were several inches of water throughout the entire basement. From the visible evidence and the homeowner report we have two very important pieces of information:

  1. The staining on the wall several inches above the floor confirms the presence of moisture along the joint between the foundation and floor;  and
  2. The significant amount of water observed on the basement floor (flooded basement) suggests that there was an easy path of entry for the water.

Basement leak caused by rising water table

This picture above also shows the bed of gravel beneath the open basement floor. It is clear, in this instance, that there is a substantial amount of ground water beneath this basement floor. The presence of this water confirms that there is a high water table. A high water table saturates the soil and the water table’s height is substantially influenced by the amount of precipitation and its duration. Sometimes the water table rises so rapidly, particularly during the spring, that water forces its way into the basement through the natural seam that exists between the basement floor and the foundation wall (in some instances, through floor cracks as well). Check out the video of a high water table flooding a basement.

In situations like this, no amount of exterior waterproofing will resolve this problem. 

Here is an illustration of how a high water table ends up on your basement floor.

Rising water table flooding the basement

In this particular room we found no evidence whatsoever that water had come through the foundation; so where did the water come from? In this instance, the basement leak was simply the result of a rising water table beneath the home.

How to fix this type of basement leak

This type of basement leak can only be fixed by ensuring that the water table beneath the basement floor is not permitted to rise to the point where water can push up through gaps in the basement floor. As the weeping tile is installed around the exterior of the home next to the footing, installation of new weeping tile will not resolve this type of basement leak. The only way to control the height of a rising water table beneath a basement is by using a specially configured sump pump and liner like the one in the image below. Note the water rushing into the sump pump liner (through the walls at the bottom of the liner).

Water draining into sump pump liner
 Note the water under the basement floor rushing into the sump liner

Click on this hyperlink for more information on sources of basement leaks.



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Topics: weeping tile replacement