Why Does My Concrete Floor Sweat in Humidity?

Updated April 17, 2017

A lot of homeowners and maintenance administrators have noticed that concrete floors “sweat,” or produce moisture, in humidity. Aside from being a slight annoyance, the effect can actually cause several problems for flooring and safety as well.


Sweat on a concrete floor produces a safety risk for you and other people. It can cause unwanted slips and slides, which could lead to accidents and injuries. It can also cause problems with the adhesion of floor-covering materials such as tile, carpet, sheet flooring as well as bond-related failures of nonbreathable floor coatings. A lot of the adhesives used in floor coverings today are more water-sensitive than in the past, and the sweat in a concrete floor can only make things worse.


There are many possible sources of concrete moisture. One of them is underground water. If your floor is placed over saturated ground or if there is poor water drainage in the area, moisture can move to the floor surface through a process of capillary action, also known as wicking.

The Soil Below

The depth of the water table and the fineness of the soil below the concrete are some of the factors that affect floor moisture. If the soil below the concrete is damp, water vapour will diffuse and eventually condense on the floor surface. This happens when the floor touching the soil is cooler and at a lower relative humidity. This is caused by a vapour pressure gradient.

Effects of the Initial Processes

During the installation of the concrete floor, if the fill course or blotter layer is wetted, the trapped moisture will eventually escape through the slab and end up on the surface. Going further back from the installation process, residual moisture from when the concrete was originally mixed will move toward the surface eventually. It usually takes six weeks to a year for the concrete to completely dry.

Avoiding Moisture

To avoid having a concrete floor that sweats, ensure that proper drainage is designed away from your flooring. Make sure to use a concrete mixture with a low water-cement material ratio. Also allow the floor to dry up within a reasonable amount of time. Try to avoid cleaning the floor with water and make sure to check the floor’s moisture condition before installing any floor covering. If you’re unsure, consult the opinion of an expert. Work closely with your contractor or home renovator and be sure to point out this specific problem.

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