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Hydrostatic Pressure

When water saturates poorly draining soil, it will start pushing against basement walls, causing them to bow or crack. This is called hydrostatic pressure.

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Hydrostatic pressure can have a damaging effect on your foundation walls and the basement. Over time, it can cause your basement walls to bow or crack, allowing water to enter your home. Homes in Denver, CO, that sit close to a temporary water table are the most vulnerable. Let’s explore hydrostatic pressure, a common and often misunderstood water-related foundation issue. 

What Is Hydrostatic Pressure? 

Hydrostatic pressure is the vertical and horizontal force that standing water exerts on any object or surface that stands in its way. When contractors install a concrete slab beneath the water table, hydrostatic pressure will push against the slab walls.  

The wetter the soil gets, the more pressure it will exert on your walls. This water buildup can lead to a host of structural issues. In extreme cases, this pressure can cause your walls to collapse.  

Upward moving water pressure also dissolves concrete salts and becomes alkaline. It’s this alkalinity that causes the concrete to lose its binding properties. This creates more cracks and pores in your foundation and causes your concrete floors to degenerate.   

What Causes Hydrostatic Pressure? 

Soil saturation may be the leading cause of hydrostatic pressure, but it is not the only one. 

  • Poor water drainage: Broken sprinklers, city mains, plumbing, and other water supply lines can also cause the soil in your yard or lawn to get wet.  
  • Improperly dried concrete: Applying surface membranes before the slab dries up completely can also cause moisture to accumulate below or next to your concrete slabs.  
  • Inadequate installation: Sometimes, less experienced flooring and concrete professionals fail to survey the construction site properly or do not use vapor barriers with low permeability ratings. Geotechnical surveyors may also forget to locate nearby water sources. All these will result in hydrostatic pressure.  

Determining Hydrostatic Pressure 

The easiest way to test for hydrostatic pressure is by drilling a hole on your concrete foundation’s surface. Wait a day or two to see if the concrete becomes dark. You can also test hydrostatic pressure by placing a plastic sheet over your basement floor and holding it down with duct tape to see if water droplets form on top of it.  

Concrete epoxy moisture meters will also come in handy in testing hydrostatic pressure. If the moisture content is above 5%, your foundation is at risk of moisture issues.  

Another effective way is to use the calcium chloride test, a surface-based evaluation of concrete moisture, which measures moisture emission rate over a thousand square feet of space within a 24-hour window. This method is not ideal for lightweight concrete. 

A more effective approach is the relative humidity (RH) test. This test uses a probe to measure the moisture concentration deep in the foundation slab. 

How to Fix Hydrostatic Pressure 

Water is a dense liquid that weighs about 60 pounds per cubic foot. Whenever it rains, hydrostatic pressure can build up to thousands of pounds. Such extreme pressure has the potential to damage your foundation walls. To avert these problems, you have to control hydrostatic pressure by eliminating water sources near your home. 

Pressure Relief 

You can reduce hydrostatic pressure around your foundation by diverting water away from it. If you have poorly draining soils, consider installing a sheet drainage material on the ground. What this does is enhance water movement to the foundation drain, significantly reducing the amount of water that pushes against your walls.  

Contractors can also help you reduce hydrostatic pressure by setting up an internal drainage system like BasementGutter™. This device will collect any leaking water and direct it to a sump pump system before it has the chance to turn your basement floor into a waterpark.  

Grading your yard or lawn is another effective method of reducing hydrostatic pressure in the soils around your home. What this does is enable water to flow out and away from your home’s perimeter. 

Your gutters and downspouts need to be in good shape to drain water away from the roof. Make sure they’re clog-free and fastened properly. Otherwise, water will pour down the sides of the walls and collect around your foundation. 

Waterproofing 

Once you grade your yard and implement other exterior drainage measures, you will need to consider additional waterproofing solutions that can help you keep water out of your foundation. One of these is installing a waterproof barrier between the foundation’s slab or wall and the water source. Such a barrier will stop water from poorly drained soils or a high water table from infiltrating your walls.  

Do you have leaking foundation walls? Contact Complete Basement Systems today to schedule a free foundation inspection. Our skilled technicians will identify the cause of dampness and recommend a lasting solution. 

Serving Greater Denver area, Colorado Springs, Eastern Colorado, and parts of Nebraska and Wyoming

Complete Basement Systems, Colorado Springs, CO

5695 Parachute Cir
Colorado Springs, CO 80916

Complete Basement Systems, Denver, CO

11795 E. 45th Avenue
Denver, CO 80239