Understanding, Preventing and Correcting Concrete Moisture Problems
Incorporating independent concrete moisture testing into project specifications is the most effective means of preventing flooring failures
In order to fully understand the causes and prevention of concrete moisture problems, it’s important to start with a basic understanding of the composition of concrete, and the chemical reaction between cement and other elements in concrete.
Concrete is typically a mixture of cement, water, coarse and fine aggregates and admixtures. The proportions of each material in the mixture (mix design) affect the properties of the concrete, so different combinations are used for different applications and uses.
In any case, the cement, when mixed with water, forms a paste that acts like glue and holds the mixture together. This chemical reaction will strengthen the concrete over time, as long as there is moisture present to react with the cement (curing). While water is concrete’s “friend” in providing its strength over time, it is ultimately your floor coverings enemy when it comes time to install the floor.
Issues leading to concrete moisture problems
There are many reasons why the moisture content of concrete is an increasing concern. Here are just a few.
Reason #1: Modern day construction timetables are growing shorter and shorter.
With the rise of fast track construction and advances in technology, what used to take a year to build can now be built in just a few months. Waiting several months for the concrete to dry is not an option, so many products have been developed to either accelerate the concretes drying time and/or to block the moisture at the surface of the concrete. Unfortunately, the time it takes for placement, curing, and drying of concrete has not been reduced in the same manner. The result is concrete slabs with moisture content well above the limits of the floor coverings when it comes time to install the flooring.
Reason #2: A vapor retarder is either ineffective or not present.
A vapor retarder is the most proven way to protect floor coverings from under slab moisture. For many years, the construction industry did not require vapor retarders as a standard practice on all slabs to receive floor coverings. When vapor retarders were used, they were often improperly placed, and/or made from low grade materials which deteriorated over time. As a result, we have many aged concrete slabs in building structures today that are not properly protected from sub slab moisture. Due to inadequate information on aged slabs, such as the presence of a vapor retarder, its condition, and whether it was installed properly -- are all reasons why moisture testing is still recommended.
Reason #3: Changing environmental regulations
The flooring industry, its products, and its by products are all regulated by various federal, state, and local agencies. Changes in regulations have forced manufacturers to reformulate their products to remove many of the harmful chemicals, resulting in products that are more sensitive to concrete moisture. For example, asbestos is no longer an ingredient in flooring material, and many dangerous solvents have been removed from adhesives. These changes have led to the increasing need for a concrete moisture testing prior to the installation of flooring.
Application of flooring materials to concrete
Ultimately, the science of concrete creates a flooring dilemma: Moisture, while good for concrete strength, will break down adhesives used to bond the flooring to the substrate and can lead to a shorter floor shelf life and floor failures. Considering all the factors stated above, it is nearly impossible to predict the moisture conditions of your concrete or your risk of having a moisture related failure, without adequate concrete moisture testing.
Prevention of Moisture-related Flooring Problems: Clear Project Specifications are the Starting Point
To prevent moisture-related flooring problems, you must understand the moisture content within the concrete, the flooring products, and the adhesives, so that all of them are compatible. Some adhesives have higher moisture tolerances and some lower, and the same goes for flooring materials.
Everyone involved in the decision-making process regarding concrete slabs and flooring, from the architect to the flooring installer, needs to have a clear understanding of the project specifications. Clear project specifications include detailed information regarding manufacturer’s guidelines for the moisture tolerances of the flooring and adhesives that will be used in the project.
How to Determine if the Conditions are Right: Concrete Slab Moisture Testing
At some point before flooring is installed, the concrete has to be tested for moisture content. There are two primary concrete slab moisture tests:
Test #1: Calcium Chloride/ Moisture Vapor Emission Rate (MVER) testing:
This test is known as the ASTM F1869 “Standard Test Method for Measuring Moisture Vapor Emission Rate of Concrete Subfloor Using Anhydrous Calcium Chloride.” The test provides information about how much moisture is being emitted from the top portion of the concrete. However, because this is only a surface emission test, alone, the calcium chloride MVER test may not provide sufficient information on which to base a flooring installation decision.
Test #2: Relative Humidity (RH) testing:
This test is known as the ASTM F2170 “Standard Test Method for Determining Relative Humidity in Concrete Floor Slabs Using in situ Probes.” Testing with this method provides valuable information about how much moisture is within the concrete. Because this test only addresses moisture within the slab and not the movement of the moisture, like calcium chloride,RH testing may not provide sufficient information on which to base a flooring installation decision.
Correction of concrete moisture problems
Identifying the concrete moisture content is only half the battle. Once the moisture is identified, considerations such as timing, budget, and product options are all influential factors when determining the best flooring solution. Having an unbiased, third party partner to help you weigh these factors is important.
As an independent, third-party testing company, with over 20 years of experience, IFTI offers an unbiased assessment of the concrete slab condition, as well as recommendations for the best products for the job. If you have any questions related to project specifications, concrete moisture testing or have a flooring problem, please contact us at 800-490-3657 for a complimentary consultation.