Moisture is among the greatest enemies of quality surface prep or concrete coating. Moisture on surfaces, in the air, and in your machinery may lead to many issues. That’s why we put together this post on how moisture affects your concrete and give you tips on preventing it. 

At its worst, moisture can cause you and your team to waste precious time and resources as you work to undo the damage done. What’s worse, left unchecked, coating pitfalls from moisture may make for some unhappy property owners and lost customers. 

Knowing the potential effects of moisture on your coat will help you be more diligent in combating surface prep disasters and ensuring a good quality finish. 


The more common problems caused by moisture include:

  • Microscopic level. Moisture-related problems in surface coating often start at a microscopic level where water particles interfere with the bond between the coating and the concrete. This interference can significantly compromise the adhesion, leading to issues such as peeling or flaking over time. 
  • Environmental level. Moist environments also accelerate the curing time of some coatings, which might sound beneficial but can lead to incomplete curing at deeper coating layers. This uneven curing process can weaken the overall structural integrity of the coating, making it susceptible to further damage from physical impacts or thermal cycling.
  • Chemical Reaction. Furthermore, high moisture levels can react chemically with some aspects of the coating formula. For example, water can cause hydrolysis reactions in some polyurethane and epoxy coatings, leading to a breakdown of the chemical structure. 

This breakdown diminishes the coating’s physical properties and can lead to discoloration, a significant concern in aesthetically sensitive areas. 

Thus, understanding these moisture interactions helps select the appropriate type of coating and the necessary surface preparation techniques to mitigate moisture impact and ensure a durable, high-quality finish.


Moisture in concrete can significantly impact its durability and structural integrity. Excessive moisture content can lead to problems such as efflorescence, where salts rise to the surface, creating a white, powdery residue that can weaken the surface. 

Moisture can also promote the growth of mold and bacteria, which degrade the concrete’s integrity over time. 

Additionally, moisture expansion can cause cracking and spalling, whereby chunks of concrete dislodge from the surface, compromising the structural soundness of the concrete. 

Understanding these effects helps in selecting appropriate drying and sealing techniques to ensure the longevity and safety of concrete structures.


Flash rust occurs when moisture enters your surface before applying the first surface coat. When this happens, the coat fails to adhere correctly, and the coating fails. You may only realize you have an adhesion issue once it’s too late and you’ve begun your second coat. 

Therefore, keeping your surface dry before the first application is essential.

The mechanics of flash rust involve rapid oxidation facilitated by moisture, often exacerbated in environments with high salt content or pollutants. This oxidation forms a weak layer of rust that prevents the coating from bonding directly to the concrete, leading to adhesion failures. 

To mitigate bonding problems, ensure your surface preparation includes thorough cleaning and potentially the application of rust inhibitors or primers that seal the surface and block moisture penetration.


Delamination may occur if significant humidity enhances condensation or moisture on your surface. It results in the fracturing of a coat into layers, making your coating job appear cratered, ugly, and even incomplete.  

In environments with fluctuating temperatures and humidity levels, the risk of delamination increases as these conditions can cause the moisture trapped beneath the surface to expand and contract. This physical stress disrupts the bond between the coating and the substrate. 

Preventive measures include using moisture-tolerant primers and ensuring that the environmental conditions are controlled during the application and curing phases to maintain a stable moisture level.


If you’ve ever seen out-of-place pores or bubbles on a finished surface, you’ve seen a floor blistering from a moisture-compromised coat. That’s because too much condensation on the surface before coating causes blistering.

There’s no getting around blistering without first taking steps to prevent it. One way or another, the water under a layer of coating – as it evaporates – will escape, leaving a constellation of nasty blisters all over your once-beautiful floor.


Proper control of the water content in the concrete mix is essential for maintaining its strength, especially in load-bearing applications.

The amount of water added to the concrete mix allows you to achieve optimal strength and durability. Water facilitates the chemical process of hydration, which is necessary for the concrete to set and develop strength. 

However, an excessive water-to-cement ratio can dilute the mix, reducing strength and increasing porosity. This porosity makes the concrete more susceptible to freeze-thaw cycles and chemical attacks, which can further degrade the material. 


There are times when the moisture is easy to spot and remove – some droplets along the surface or an apparent humidity in the air. But there are also times when the moisture isn’t so obvious. 

When working with concrete, for example, moisture may be underneath that is not visible to the human eye or when you graze the surface with your fingertips. 

The following ways help combat moisture and prevent it from causing issues down the road:

  1. Dehumidification
  2. Testing
  3. Sweep, scrub, dry


If you’re looking for a simple and efficient means of removing moisture, dehumidifying the space and the air inside a blaster’s tank will help prevent serious issues. Dehumidifying before coating may prevent blistering and poor adhesion. It may also increase the longevity of your final polished coat.

Technological Solutions for Moisture Detection

Technology advancements have introduced sophisticated tools that can more accurately detect and quantify moisture levels in concrete. Moisture meters, for example, provide instant readings and can help identify hidden damp spots not visible on the surface. 

Additionally, an infrared camera can visualize moisture distribution across a large area. Infrared helps professionals pinpoint problem areas quickly and efficiently. Incorporating these tools into routine checks before commencing surface preparation can prevent moisture-related problems from developing.

Best Practices for Dehumidification

Effective dehumidification depends mainly on understanding the specific needs of the project environment. For indoor projects, using commercial-grade dehumidifiers can help maintain an optimal humidity level, especially in climates prone to high moisture. 

It’s essential to monitor the humidity levels continuously with hygrometers and adjust your dehumidification strategy accordingly. 

For best results, seal off the space from external moisture sources during dehumidification.


Testing the surface is another way to prevent moisture-related pitfalls. You can test with a concrete testing device or by sealing a plastic sheet over the concrete surface and leaving it there overnight. 

When you return to your plastic sheet, remove it and check if moisture has collected.

Types of Moisture Tests for Concrete

While dehumidification and testing can undoubtedly help in hard-to-tell situations, performing your due diligence in general cleaning before coating is of utmost importance for the quality of your coat. Your concrete coating can only do so much if you’re not genuinely trying to keep the surface clean. 

Both methods provide data to help decide if additional steps are needed before you proceed with surface coatings: additional drying time or moisture mitigation strategies.


First and foremost, how thoroughly are you preparing your surface for coating? 

While dehumidification and testing can undoubtedly help in hard-to-tell situations, performing your due diligence in general cleaning before coating is of utmost importance for the quality of your coat. Your concrete coating can only do so much if you’re not making genuine efforts to keep the surface clean.  

Comprehensive Cleaning Techniques

A thorough cleaning regimen is vital for successful coating applications:

  1. Begin by sweeping to remove loose debris and scrubbing with a high-quality cleaner that can reduce surface contamination. 
  2. After scrubbing, mopping with clean water will remove any residual cleaning agent and loose particles.
  3. Finally, dry the surface completely with air movers or fans to ensure it is free from moisture. 

Employing these detailed steps ensures that the concrete surface is impeccably clean and ready for coating, reducing the risk of adhesion issues.

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