As contractors, we all know how important it is to keep an eye on the weather forecast. Rain, wind, heat, and freezing temperatures can make or break a coatings job.
However, there’s another weather factor that quietly ruins more coating projects than most contractors realize: the dew point.
If you’ve ever had a floor start to turn cloudy, lose adhesion, or just look slightly off after application, there is a solid chance that the dew point played a part in that failure. This small, invisible line between temperature and humidity determines when condensation will form on the concrete. If you do not respect the dew point, your coating can fail before it even has a chance to cure properly.
In this article, we’ll break down what the dew point actually is, why it matters so much for decorative concrete coatings, and how you can keep an eye on it during every project to avoid costly mistakes.
As Benjamin Franklin once said, “By failing to prepare, you are preparing to fail.”
What Is Dew Point?
Dew point is equal to the temperature at which condensation begins to form on a surface, depending upon the amount of moisture in the immediate, surrounding atmosphere. The surface you’re coating, most often the floor, is the one you need to watch for condensation.
Essentially, when the substrate temperature is within 5°F (≈3°C) of the dew point temperature, condensation forms on the floor’s surface. This can cause complications and issues with the coating if the decision is to proceed with the work.
To put it simply, this concept is similar to condensation forming on a cold glass of water on a humid day. The concrete slab can “sweat” if it is cooler than the air can hold moisture against.
Always remember: the substrate is the surface that matters most.
Why Dew Point Matters to Coatings Contractors
If you do decide to continue with the job during a critical dew point period, the look of the floor or the adhesion to the floor or to the previous coat will be compromised.
For example, applying a urethane when the surface temperatures are within 5°F of the dew point may cause the surface to turn cloudy due to moisture. As air temperature rises, it can hold more moisture; as it cools, it holds less.
Seasonal transitions and early mornings tend to be high-risk periods because air temperatures and humidity swing more. Even if there is no visible condensation, it can still compromise both adhesion and durability, so make sure you are taking the proper precautions before wasting time, money, and product.
How to Monitor & Manage Dew Point on the Job
As a rule of thumb, only apply your coatings when the substrate is at least 5°F warmer than the dew point. This simple step significantly reduces the risk of surface failure and saves you the frustration of redoing work, because we all know how frustrating that can be.
To do this, you don’t need any fancy tools. Most smartphone weather apps can help you monitor the temperature, humidity, and dew point forecasts. If you have the means to invest, you can pick up a handheld meter for on-site readings of temperature and humidity.
Now, say you do all of your checks, but the conditions are borderline, causing you to feel uncertain about whether to proceed or not. In this case, consider the following:
- Wait until the temperature rises above safe levels.
- Increase air circulation on site with fans.
- Use dehumidifiers to reduce moisture.
- Avoid early morning applications, when surfaces are coolest.
All in all, monitoring the dew point temperature should be as routine as checking for rain in the forecast. Both are equally important, and every contractor should make dew point checks a standard part of their routine when applying decorative concrete coatings.
For more information, follow us on Facebook and visit our online Decorative Concrete University for additional surface application tips.
Reserve Your Seat at Our In-Person Training Classes in Lima, OH!