Condensation – What is it. Why is it there. How to deal with it.

By David P. Seland

Principal, ISE Logik Industries

Read full article in The Flooring Contractor

Condensation occurs when air, saturated with water vapor, reaches a dew point temperature. When this temperature is reached, moisture forms on the surface of an object, resulting in what we know as condensation. 


Condensation is moisture vapor in the air that condenses on a surface.

Meteorologists use dew points to describe how much moisture is in the air—the temperature that air must cool to reach saturation if moisture content and air pressure are constant. For example, if the weatherman states that the dew point temperature is 55°F, water will condense on a solid surface when its temperature falls to 55° or below.  This phenomenon is what causes beads of water to form on a glass of iced tea on a hot summer day; the surface temperature of the glass filled with ice is below the dew point temperature and the water vapor in the air creates condensation on its surface. 

The same phenomenon can occur on a substrate surface if that surface is colder than the dew point temperature of the ambient air above.  Just as with the glass of iced tea, moisture vapor in the air can condense on the substrate surface.  When this happens with concrete, it is commonly referred to as “concrete sweating” or “sweating slab syndrome”.  

Several environmental factors related to condensation have a significant impact on the success of a floorcovering installation. Among the most important are ambient relative humidity and ambient temperature, substrate surface temperature, and dew point. Consider the following five important factors relative to condensation control: 1) The climate controlled systems in place at a jobsite, 2) what settings they are on for controlling ambient temperature and ambient humidity, 3) whether continuous or non-continuous operation, 4) the efficacy of those climate controlled systems, and 5) air leakage into the building such as open areas for construction traffic. Problems occur when the substrate’s surface temperature matches the dew point temperature. This is more likely to happen late at night or in the early morning hours. When a substrate’s surface reaches the dew point temperature, the resulting condensation delivers a surface that is simply not ready for floorcovering installation.


Condensation adds moisture to the adhesive under carpet tile.

Complicating the issue of condensation is the lack of an accepted definition of the term “surface dry” in official floorcovering industry standards or practices.  As an example, F710 Standard Practice for Preparing Concrete Floors to Receive Resilient Flooring has stated for almost a decade that “the surface of concrete floors to receive resilient flooring shall be dry…” yet nowhere is “surface dry” clearly defined.  Though it is true that the Carpet and Rug Institute and many adhesive and flooring manufacturers  clearly state to avoid applying floorcovering materials unless the substrate surface temperature is at least 5°F higher than the dew point, the term “surface dry” remains undefined.  

Of course it is always critical to refer to the manufacturers’ specifications and follow the required acceptable ambient relative humidity and temperature levels, surface temperature, and dew point spread for the specific products you are installing.  However, in the absence of any specific guidance, avoid installing any flooring product unless the substrate is surface dry; with “surface dry” being defined as the complete absence of any visible dampness, water, snow, ice (or other precipitation) on the substrate surface, and with ambient conditions at least 5°F above dew point with the temperature rising.


Condensation adds moisture to the adhesive under LVT.

In a post-installation floorcovering failure, condensation’s detrimental effects are typically misdiagnosed as a “classic moisture issue”.  Reaching dew point and the resulting condensation are momentary effects that can be avoided and controlled on the jobsite. Even with common floorcovering adhesives, and the presence of sufficient added moisture from condensation, the adhesive appears as in the same state it was in the bucket. The adhesive in this state under the floorcovering can migrate through the adjoining seams as the environment seeks to achieve equilibrium, which is further exacerbated when foot and rolling traffic are applied. Commonly, attempts are made to remove this adhesive residue with cleaning procedures, only to return once foot and rolling traffic are applied. Further adding to confusion, dew point and condensation may have affected only the floorcovering that was installed in the early morning hours, but as the day progressed and dew point conditions evaporated, the balance of the same floorcovering installation for that day does not show any signs of a “classic moisture issue”. 

Frequently, the interior environment of the jobsite is not sufficiently climate controlled, and even ignored when ambient temperatures are considered “moderate” or no potential for freezing conditions. It is not unusual on these jobsites that dew point is reached, and condensation occurs as a result almost daily. When applying floorcovering adhesives in these conditions, the floorcovering installer is faced with an “open time” requirement for the adhesive that is extended exponentially beyond what the installation instructions state on the bucket. As the installer faces a time and labor cost quandary induced by this condition, often the floorcovering is placed into the adhesive that is still too wet, only to have it manifest its negative effects soon after. 

Critical in avoiding dew point caused problems is for the installer to be aware of the environment in which the floorcovering will be installed, and frequently conduct ambient temperature and relative humidity, surface temperature, and dew point measurements of the area and substrate surface temperature measurements. These can be readily conducted with digital devices that produce immediate data: A hygrometer measuring ambient relative humidity, thermometer measuring ambient air temperature, thermometer measuring surface temperature, and a dew point meter. Devices are available that are a combination of two or more of these functions. Additionally, devices can be set to provide continuous monitoring and real time measurement data during the entire floor prep and floorcovering installation process. 

Floor covering contractors and installers must be aware of condensation at the job site and never underestimate the adverse effects it can have on the success of a flooring installation. Condensation is a fact of life—it’s just basic science. But ignoring it can really complicate your install.  The negative effects of condensation on floorcovering installations are easily preventable. Only install under surface dry conditions. Always maintain the surface temperature 5°F or more above the dew point temperature and rising.  And always document and maintain the test measurement data as you work the project.