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Why Does My Concrete Basement or Garage Floor Sweat?

New Concrete Experience Condensation? - Image 1Concrete is one of the most widely used construction materials around the world, thanks to its durability and strength. Most internal waterproofing system will have some concrete removed and new concrete installed after the system is installed. When concrete is poured, it goes through a process called curing, where it gradually hardens and gains its strength over time (Approximately 30-days). However, one phenomenon that can occur during the curing process is the development of condensation on the concrete surface in high humidity situations, particularly in basements where there is limited air circulation. In this blog post we will explore the reasons behind this wetness and how it can be prevented.

Understanding the Basics of Concrete Curing

Before delving into the causes of condensation on curing concrete, it is essential to understand the basics of the curing process itself. Concrete curing is a chemical reaction between water and cement, which transforms the mixture from a wet, pliable state to a hardened and strong material. During this process, water is slowly released from the mixture, which creates tiny spaces in the concrete, known as capillaries. As the concrete hardens, the capillaries become smaller, and the concrete becomes denser and more resistant to moisture. This happens with all concrete.

The curing process takes place over a period of several days to several weeks, depending on various factors, such as temperature, humidity, and the type of cement used. The curing process is most effective in a humid environment, which helps to keep the concrete moist and prevent it from drying out too quickly. However, if the humidity level is too high, it can lead to the development of condensation on the concrete surface.

Why Does Condensation Occur on Curing Concrete?

There are several reasons why condensation can develop on curing concrete in high humidity situations. The most common causes are:

  1. Temperature Differences: When warm, moist air comes into contact with a cooler concrete surface, the air cools down, and the moisture in the air condenses on the concrete. This phenomenon is similar to the formation of dew on grass in the morning. In basements, where the air is often cooler than in other parts of the house, this temperature difference can be more pronounced, leading to condensation on the concrete. Since this concrete was placed in a basement or below grade space, the ground temperature (usually around 55-degrees) makes the concrete cooler and prone to condensation until the curing cycle is complete.  Garage floors are notorious for having “sweating” or condensation in the summer. The slab becomes cold overnight and then, in the morning, the garage door is opened up and warm humid air hits the slab. This creates a layer of moisture on the whole slab.

  2. Limited Air Circulation: Basements are often poorly ventilated, which means that there is limited air circulation. This can lead to a build-up of moisture in the air, which can condense on the concrete surface. Additionally, since some customers elect NOT to get a Sedona High Performance Basement Air Machine, they have only addressed the liquid water penetration and still likely have a problem with too much moisture in then air. Please note that most of this moisture is coming through the walls, integral garages via air infiltration. The moisture is suspended in the air until it comes in contact with a cold surface and condenses. This is exactly that same as when a cold glass of ice water forms water on the outside of the glass on a hot summer day. There is nothing wrong with the glass. No water is leaking. It is simply the fact that as air is cooled it cannot hold as much water, and thus condenses on the colder surfaces…in this example the outside of the glass.

  3. High Humidity Levels: When the humidity level in the air is high, the air can hold more moisture. As a result, there is a greater likelihood of condensation forming on the concrete surface. High humidity levels can be caused by a variety of factors, such as weather conditions, indoor activities (e.g., showering or cooking), and the presence of moisture in the basement air from outside.


It is very easy to determine whether you have water coming up through the concrete floor or condensation. You simply get some duct tape and a piece of aluminum foil. You then tape the foil down on the floor and wait 24-48 hours. If water droplets appear on top of the foil, the water is absolutely from condensation, as water could not migrate upward through the concrete and then through the foil. If the floor is wet everywhere EXCEPT on top of the foil, and when you peal back the tape and foil the concrete is wet underneath, that may indicate water coming up through the floor.


Preventing Condensation on Curing Concrete

Preventing condensation on curing concrete simply requires patience. Once the concrete has cured it is inert and will act similar to the original concrete. That said, an internal french drain will not stop humid air from entering the home, ever. It stops liquid water penetration and has absolutely no influence on moisture in the air. If you are having persistent condensation you likely require a Sedona High Performance Basement Air Machine for your home.  Click HERE to learn more about the features and benefits of this machine and why it is significantly superior to a traditional dehumidifier. 



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Aaron Stull
Aaron Stull is a second generation foundation repair specialist from the greater Pittsburgh, Pennsylvania area.

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