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Why Is Your Basement Leaking: The Answer May Surprise You

Leaking Basement

A leaking basement is never a good thing, but it's an issue that many homeowners share. Unfortunately, regardless of how well protected a basement is, at some point, there's a good chance it'll need attention to prevent leaking. Determining the source of a minor leak can be a critical step in preventing an expensive basement flood. 

The Tell Tale Signs That You Have a Leaking Basement 

If you are a homeowner with a basement, you might as well get used to the idea that basements are prone to leaking. This is because water tends to take the path of least resistance. Since a basement is the lowest level in a home, it tends to be like a magnet to unwanted water. 

Keeping an eye out for the critical warning signs of basement flooding ​can help you get a jump on any leaking issues that may be in the early stages of a major problem. If you know the causes of flooding basement and know how to prevent leaks from starting, you'll be able to save a lot of time and money. 

When you find a pool of water on the floor, it's pretty obvious that there's a problem. But other times, a leak can be tricky to detect . . . especially if you're not looking for the subtle signs.

Here are a few of indicators that may point you in the direction of a basement leak: ​

  • Mold and Mildew: Mold and mildew are often found near areas that have been exposed to moisture. Mold frequently has spores that can be inhaled. This can cause respiratory issues and trigger allergies. 
  • Rust Stains: Rust is formed by oxidation and it's a clear indiction that there's moisture exposure. Look for a reddish flaky layer of iron oxide, It can be commonly found on metal surfaces, such as steel or iron.
  • Efflorescence: A white mineral deposit that's often powdery or fuzzy. Efflorescence is typically seen on brick, concrete, and tiles. Minerals, such as salts, are carried by water thru masonry materials. As water passes thru the foundation's wall, the minerals within the water are dissolved within the masonry material. When the water evaporates, the minerals are left on the surface in a white, powdery film.
  • Rotting or Wet Wood: Wood rots when it's  exposed to moisture. If the moisture content of the wood goes above 30% (Fiber Saturation Point) wood decay spores will find their way to the surface of the wood. When wood decay spores are exposed to air, and the temperature rises, the spores germinate and penetrate the wood. 
  • Floor Stains: If your floors are stained it could be an indication of water absorption from a leak. 
  • Drylock Flake: Basement foundations are built with porous materials, commonly concrete, and moisture and water can easily seep thru. Drylock (also known as Drylok) is a common waterproofing concrete sealant that's designed to keep water out of your basement. However, if it's not properly applied (generally to surfaces that have not been adequately sealed) the product will bubble and eventually flake off.
  • Seepage: Water seepage frequently occurs when water is coming through cracks in the foundation or other porous material. It's quite common to see dampness or staining around floor cracks when seeping is taking place.
  • Wall Cracks: Frequently a crack will form since concrete shrinks as it cures. However, cracks could also be an indication that the foundation has settled and damage has occurred. When wall cracks happen in basements, there are 2 main types, and both can be the cause of seepage in your basement.
    1. Vertical or diagonal cracks - These types of cracks are common as your foundation ages. 
    2. Horizontal Cracks - These are the most serious types of cracks because they are caused by lateral pressure against the walls. 

What Causes a Basement to Leak?

Window Wells - Finding water around your window wells is a common way to discover your basement is leaking. This type of leaking is not related to ground water pressure like the other 2 types below.

Windows are installed in basements to allow light and air in, however, during heavy rains water can collect within the window well. This can also happen if there are drainage issues around your home.​

The more water collecting within the window well the more pressure is placed upon the window itself. The result can be seepage thru cracks or gaps around the window. 

​One of the more common causes of basement flooding is seen when water becomes trapped in the window well outside. When this happens, the pressure on the window and it's seals increases. When enough pressure builds, the seal eventually fails and water begins to seep or spill in causing a huge mess. This disaster can usually be spotted early by watching for seepage, as water tends to find cracks and gaps around windows. 

Hydrostatic Pressure - In simple terms this is the amount of pressure exerted by a fluid. The pressure is heavily influenced by the water table within the ground. 

The water table is the level below ground that's saturated with water. It not only differs by location, such a living by a lake or in a desert, but it also changes with each season. During the Winter, when there tends to be heavy rains or melting snow, the water table is higher than during the Summer.

Water tables do not rise until the soil becomes saturated and unable to absorb anymore liquid. Hydrostatic pressure increases on your home's foundation as the water table rises underneath your home. The water must find somewhere to go, and if your foundation is the path of least resistance, it will find itself inside your basement.

Lateral Pressure - Lateral pressure happens when the soil surrounding your home expands and increases the pressure against the foundation. It not only can cause leaks, but it can also cause serious damage to your foundation.

A home's foundation can typically deal with normal weather conditions because the soil can usually drain adequately. However, during heavy rains or melting snow the threat from lateral pressure can be quite high.

When your home was built, the soil needed to be excavated and then it was backfilled when your house was finished. The soil surrounding your home is not nearly as compact because it was excavated. The looser the soil, the more water the soil will be able to absorb. As absorption increases, the soil expands and places pressure on the walls of your foundation and can eventually cause a crack.

The type of soil that surrounds your home also makes a difference. Soils such as sand are capable of draining quickly and absorb very little. However, clay will absorb more water and put more pressure on the walls of your foundation as the clay expands.

To make a bad situation worse, if your gutters are clogged and your downspouts do not direct the water far enough away from the house, a build-up of water can develop near the foundation creating even more lateral pressure and increasing the likelihood of leakage. ​

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