Testing concrete slabs for excess moisture has become a common construction requirement according to today’s general contractors, especially when installing flooring. While several standard moisture test methods are available, no single test reveals everything that should be taken into consideration when it comes to deciding when flooring is safe to be installed or a coating applied.

Speaking with various flooring professionals throughout the U.S. helped provide more insight about high-moisture situations and how the industry has been responding to the ever-growing issue. Panelists include Mark Long, technical director at Stauf USA; Steve Taylor, director of architecture and technical marketing at Custom Building Products; Ron Loffredo, technical adviser at H.B. Fuller Construction Products; Tom Laurenzi, president of Delmhorst Instrument Co.; Jason Spangler, Wagner Meters’ Rapid RH product sales manager; Mathias Chenal, manager of patching & moisture control at Ardex Americas; Daniel Tallman, project manager of business development, and David Stowell, technical director, of HPS Schönox; Kirk Kazienko, technical sales manager at USG; Mark Lammano, technical market manager of flooring for Franklin International (Titebond brand); J. Alex Keene, manager of the floor division at Keene Building Products; and Sonny Callaham, technical product manager at Royal Adhesives and Sealants.


Q: As an industry, are we proactive when it comes to dealing with high-moisture situations or are we reactive?

Long: Moisture testing is the first thing we talk about when teaching or directing customers to the best product to use. With every job being different, you cannot treat them as if they are all the same. The key is knowing what level of moisture there is before proceeding.

Taylor: The floor covering industry is very proactive in dealing with moisture emission problems. Almost every floor covering will benefit from controlling moisture in the concrete slab prior to installation. There is considerable training available in all forms of media to educate the builders and installers of the issue of moisture vapor emission and the damage it can have on the flooring. New products are being introduced that will make it easier to control moisture emissions at lower cost.

Loffredo: As an industry, we must be proactive about dealing with high-moisture situations—the costs of damage or flooring failure from not mitigating moisture is just too high. Today’s flooring technologies are more sensitive to moisture than ever before, so the incentive is high to install flooring properly and avoid costly repairs. Proper installations also ensure that installers can benefit from manufacturer warranties.

“Today’s flooring technologies are more sensitive to moisture than ever before, so the incentive is high to install flooring properly and avoid costly repairs.”

– Ron Loffredo

Industry trends over the past 10 to 15 years have also made us more proactive in dealing with high-moisture situations. One trend has been the industry’s move toward green products, e.g. products without solvents or asbestos. Some innovative green products can create impervious barriers to moisture vapor emissions, so it has become more important than ever to address elevated Moisture Vapor Emission Rates (MVER). If the MVER is not addressed, issues arise that can lead to floor covering failures. Flooring dealers and general contractors have become much more proactive to make sure that moisture testing and moisture mitigation systems are specified in the bid process.

Laurenzi: I think the tendency in the past has been more reactive. But it’s no secret that high moisture levels in concrete slabs are probably the number one threat to compromise an installation. Most types of coverings being used today are at risk for failure due to moisture in the substrate. Remediation often involves removing the floor, mitigation of the substrate and then installing a new floor. Sometimes, litigation is also involved. The associated costs—both direct and indirect—can be tremendous. So this has the industry’s attention and a more proactive approach is being adopted.

Spangler: In some ways the industry has been reactive, especially when one considers that nearly $1 billion is spent every year to address flooring failures due to excess moisture in concrete. However, awareness about moisture-related problems and how to address them proactively is certainly growing. One important way in which flooring professionals have become much more proactive is by using proven methods of testing for moisture in concrete floor slabs. This is a critically important, proactive step because it’s preventative; accurate moisture testing enables floor installers to assess and identify high-moisture situations before the flooring products are installed. With an accurate moisture assessment, the risk of a serious moisture-related flooring failure can easily be minimized and avoided altogether.

Chenal: I think that globally, today, the industry has become very proactive when it comes to dealing with moisture situations. ASTM defined standards to test and detect, as well as remediate, high level of moistures in concrete. Building material manufacturers offer a wide variety of systems allowing the mitigation of different types of moisture problems. Flooring and adhesive manufacturers are specific about the maximum level of moisture that their products can withstand. In addition to that, the industry is providing a lot of education to all stakeholders to raise awareness of risks related to moisture and teach how to prevent them.

Tallman & Stowell: As a whole the industry, with the help of ASTM, has set standards which can be regarded as basic assessments for gauging the risks of potential moisture problems on any given job. We gain feedback from the multitudes of installers who join our training on types of moisture tests performed. It is unanimous that at least one if not both of the standard moisture testing methods currently provided thorough ASTM F1869 and ASTM F2170 are performed on any given job. This varies from contractor type and level of expertise in the industry.

Kazienko: As manufacturers, we are trying to encourage a proactive approach by offering products to address moisture vapor issues. Unfortunately, we are dealing with many in the construction process chain that either aren’t aware of the reasons for moisture vapor issues or the types of issues caused by moisture vapor issues so they take a reactive approach. It is crucial that, collectively, the manufacturers continue to educate decision-makers on the front side of these issues to prevent the expense and downtime of moisture vapor issues.

Lamanno: I would say 80% of installers tend to be reactive. Some 20% of the retailers we work with always use a moisture control system.

Keene: We find many installers prefer to react to a problem instead of choosing to solve the problem before it occurs. There are exceptions to this, but with the numerous advantages offered by moisture remediation, it behooves us to proactively handle moisture. The costs that are associated with fixing moisture-related failures outweigh the cost of avoiding moisture.

Callaham: Unfortunately, what I see is contractors and installers having to be reactive to moisture issues. Too many contractors don’t perform proper moisture testing and they do not realize there is a problem until there is a problem. This can be due to time on the jobsite, money in the bid or just not wanting to do them. I was once told that 80% of Calcium Chloride Tests were performed incorrectly, and I believe 80% may be low. It is very important to understand the idiosyncrasies of moisture and what truly makes a flooring installation fail.


Q: What are the approaches for testing and mitigation, and what factors are contributing to moisture issues?

Chenal: One big factor is the speed increase of construction schedules. Flooring is installed sooner and sooner in the construction process, not leaving enough time for the concrete to dry. Another factor is the renovation of older buildings where no structural vapor barrier membrane was ever installed under the slab during the construction. When an old warehouse is turned into an office space and flooring is installed, moisture becomes an issue.

Also, a few years ago, environmental concerns pushed manufacturers to move away from solvent-based to water-based adhesives, which are more sensitive to moisture. However, the technology is evolving and those adhesives are becoming less sensitive to moisture. Finally, education is another factor. In the past, job failures might not always have been identified and attributed to moisture by contractors.

Long: The flooring industry has standards set in place for testing moisture. Many companies buy the necessary equipment for proper testing, but there are still those companies that have not invested in protecting their future with the proper testing equipment. It is one of the most important steps in a successful floor installation and still many companies do not properly test before installing a floor. When everyone starts doing the proper tests, then everyone is a winner. It costs everyone in the end when companies fail to test.

Taylor: No one wants to deal with and replace flooring damaged by moisture emissions from the concrete slab, so we are seeing more and more specifiers and builders requesting a Moisture Vapor Control (MVC) system without bothering to first test the concrete slab. These easy-to-apply MVC systems don’t take long to install or cure and are good insurance to protect the flooring.

Laurenzi: The cost of not being proactive about moisture and mitigation is just too great, and as a result, more and more new projects are specified with vapor retarders that are placed under the slab on grade, and membranes and sealers applied on top of the concrete slab. These are all intended to minimize the negative impact of moisture migration through the slab to the floor covering.

There are numerous ASTM-approved tests available, but the most common being used are the Calcium Chloride Test (F1869) and the standard for in-situ Relative Humidity Testing (F2170). The Calcium Chloride Test does provide a useful snapshot of conditions at a point in time up to about 3/4” deep, but cannot tell if there is moisture migration or moisture deeper in the slab. The preferred method and the one we recommend is the in-situ test. The probes are placed in drilled holes at 40% of the slab thickness and are less sensitive to short-term fluctuations of ambient conditions. Since moisture moves through slab by diffusion, RH is a measurement of equilibrium moisture level. This measurement is an excellent prediction of the RH condition after a covering is applied and the slab comes to equilibrium.

Loffredo: Floor covering manufacturers publish the specific substrate moisture levels suitable for a successful installation. Moisture mitigation approaches vary based on the specific circumstances of the project. There are two sources of moisture that always must be addressed. First, there is moisture vapor rising to the slab from the ground water below. Second, there is the water added to concrete for mixing and flow, which is referred to as water of convenience. Whether new construction or during a remodel, floor covering installers must check the moisture level of the substrate.

When doing a remodel, professionals must consider whether the original vapor retarding system is still intact. Only testing can tell them how much moisture is present, at the time of the test procedure. Older construction materials were often more forgiving in that they allowed ground water vapor to continually disperse up through the flooring. The new, green construction flooring materials and installation products can contribute to creating a barrier impervious to moisture vapor, so the vapor cannot be released. Installers must put a system in place to keep the moisture from collecting under the flooring surface.

Topical application of a moisture vapor barrier is the most recognized means to mitigate elevated MVER. Epoxy-based coatings for elevated MVER have long been the industry’s solution to protect floor coverings. Newer coating technology has brought the next generation to single-component moisture mitigation products for green concrete substrates. It is very important that buyers carefully review the manufacturer’s support and warranty for any claims made about moisture mitigation.

Spangler: In the past, the anhydrous Calcium Chloride Test was the most frequently used method in the U.S. for assessing the moisture condition of concrete floor slabs. However, as with all surface-based methods of testing concrete moisture, studies have demonstrated that the Calcium Chloride Test is not reliable. These studies point to in-situ relative humidity (RH) testing as the only reliable method for assessing the moisture condition of concrete slabs. Fortunately, as flooring installers become informed about the drawbacks of the Calcium Chloride Test, they are turning to RH testing more and more. Manufacturers of flooring products are also increasingly recognizing the value of RH testing. Many manufacturers now provide specifications for their products that are tied specifically to RH test results.

Tallman & Stowell: Moisture conditions for concrete fall into two categories: static and dynamic. A static moisture condition is a function of how wet the internal structure of the concrete presently is (usually expressed by percentage). A dynamic moisture condition is a function of how much moisture is currently evaporating from the surface (usually expressed in pounds per 1,000 square feet per 24 hours).

Moisture testing for concrete also falls into two categories: subjective and objective. A subjective, qualitative test relies upon the person testing to make an opinion on the test result and/or condition. An objective test quantifies the result and/or condition in terms of percentage, pounds of emission and pH values. Consequently, the most meaningful tests (recognized by most flooring manufacturers and ASTM) are those that quantitatively produce an objective test result from measuring the alkalinity, static and dynamic conditions of a concrete slab.

The internal building envelope/environment conditions in which the slab is located are the contributing factors most commonly dealt with on any jobsite. Most floor underlayment, floor covering manufacturers and organizations would agree that moisture testing shall be conducted after the internal conditions of the interior buildings slab is under normal service temperature and humidity for at least 48 hours. If conditions are not acclimated appropriately, readings may not reflect actual service conditions of the environment leading to a false positive reading in the test.

Kazienko: The International Concrete Repair Institute (ICRI) is doing a great job of certifying third-party independent moisture testers by educating out how both the ASTM F1869 (Calcium Chloride) as well as the ASTM F2170 (Relative Humidity) should be done properly. Unfortunately, there are still those who don’t do the tests at all as well as those who aren’t taking the time to become educated.

Lamanno: Common testing approaches are the same ones we recommend. They include calcium chloride, in-situ probes and concrete moisture meters. Factors contributing to increased testing and mitigation are that installers either know they have a moisture issue in certain areas they install in or are reacting to a problem with moisture after installing. The approach is “test and apply.” In our opinion, no floor should be installed without a moisture barrier. Moisture content can change from results at time of testing due to high ground water or weather events.

Keene: The simplest way to test for moisture-related issues is to test the relative humidity. Once we know the RH of a slab we can determine which solution best fits the problem. Although this is not true for all professionals, we find the number one factor contributing towards proactive approaches is architectural specifications. When the architect forces moisture remediation, the problem becomes solved automatically.

Callaham: Contractors have been told to use either ASTM F1869 or ASTM F2170 for moisture testing, when in fact, they should really be doing both, especially on larger new construction projects. These two test methods quantify two totally different aspects of moisture. F2170 quantifies the amount of moisture in the slab itself, while F1869 quantifies how much of that moisture is at the surface. If both levels are high, you have an issue. With just one of the two high, it can be manageable without mitigation.


Q: Is this issue regional?

Long: I believe this is a national issue. There are regions where everyone has been taught the importance of moisture testing and how to proceed once they know the actual moisture levels. Then there are areas where very few do the moisture test.

Taylor: This can be a regional issue, as high moisture emissions are more common where the water table in the earth is closer to the surface. Interestingly, sometimes we find higher moisture emission in drier climates; this is because of the differential in relative humidity in the concrete slab and the relative humidity in the air.

Loffredo: While ambient humidity and cement components can vary by region, the two sources of moisture are consistent. Both ground water and water of convenience must be addressed no matter the region. Testing determines the values to match against the floor coverings’ limitations.

Laurenzi: Not at all. There are two main sources of moisture—the Earth and the free water from the concrete mix itself. Moisture issues in concrete slabs are everywhere. They exist in slabs below, on, or above grade. They are as commonplace in the dry desert areas of Arizona as in the more humid regions of the southeast U.S.

Spangler: No, the issues with moisture in concrete and how best to test for moisture are equally important in every region of the U.S. In fact, all concrete contains a surprising amount of water, even concrete that is considered dry. The key is to allow enough time for concrete to dry to a level that’s acceptable for a specific flooring product, and also to be sure to test the slab’s moisture condition and never assume that a slab is sufficiently dry. That’s true whether one is in the arid Southwest, the rainy Northwest, or the humid states of the Eastern Seaboard.

Chenal: I would not say that the issue is regional because we see moisture problems everywhere in the U.S., even in Arizona, which we would think is very dry. This is because very dry air can accelerate water movements as vapor is trying to reach equilibrium in the system. That being said, there are definitely areas that have more moisture problems because of local environmental conditions.

Tallman & Stowell: These issues, from our companies' experience, are not just regional, but a nationwide phenomenon.

Kazienko: I’ve done moisture mitigation CEUs from the Northeast to the Southwest and all points in between and can say that almost everyone in this business is either misinformed or ignores moisture vapor issues. An architect in Phoenix couldn’t understand how they could possibly have on-grade moisture issues a year after placement as they are in a ‘desert environment.’ A general contractor in New York didn’t understand how there could be any moisture in a 90-day-old slab on the sixteenth floor of a midtown high-rise. A flooring contractor in Chicago couldn’t believe that a renovation job at a community center built in the early 1990s with the original floor could now have moisture issues. As an industry, we have to continue to educate everyone about why moisture is an issue and how to address it proactively.

Lamanno: It can be regional, especially where concrete installations are more prevalent; raised wood subfloors face similar issues.

Keene: In some cases, yes, and this stems from public perception beyond the flooring industry. We find the drier the climate the less likely a professional is to consider moisture in their bids. This is common to other industries as well, including water problems found in siding and roofing.

Callaham: Moisture-related issues have no boundaries. From high water tables in the South to the high desert, you can have moisture issues. They just may be manifested in different ways for different reasons.

Side Bar: Latest Products

  • “Our epoxy ERP-270 has been one of our best-selling moisture sealers,” explained Long. “Where most people use a multiple roll on method or a squeegee to apply sealers, we have developed a special applicator, making it easy to apply and giving you the exact spread rate needed. When dealing with moisture, you must make sure you are applying at the proper spread rate to be effective. Stauf has also developed a urethane leveling compound to act as a leveler and a moisture barrier. ULC-500 Level-Seal is capable of creating a moisture barrier of up to 18 lbs. CC or 97% RH. This is a one-coat application for leveling at any thickness and moisture protection.”
  • “The latest epoxy moisture vapor emission barriers are easier to apply at reduced film thickness,” said Taylor. “This makes installation quicker and saves material cost over traditional barriers. Products like Custom Building Products’ CustomTech TechMVC can be applied to concrete slabs with emission rate of 25 pounds per day or 1,000 square feet and 100% RH content. This allows for earlier installation on the concrete slab to help keep projects on track.”
  • “The latest moisture mitigation products are one component coating products such as TEC LiquiDam EZ, a liquid moisture vapor barrier that does not require a primer before application of surface preparation products,” said Loffredo. “LiquiDam EZ can be directly applied to green concrete up to 100% RH and dries within four to five hours for same-day floor installation.”
  • “The Rapid RH system by Wagner Meters is a technologically advanced system for in-situ RH testing,” said Spangler. “The Rapid RH is known for its accuracy and ease of use. Now, for added convenience, the new Rapid RH Smart Reader and DataMaster app allow for seamless transfer of RH test data directly to your mobile device. The feature-rich DataMaster app is highly intuitive and is available for both iOS and Android operating systems.”
  • “Ardex MC Rapid was one of the first one-coat epoxy-based systems introduced in the market to help control moisture,” explained Chenal. “Because of its unique technology, it is still a benchmark product in the industry today. It is very versatile and can be used in new construction and renovation projects; it can deal with very high levels of moisture up to a 100% RH. More recently, we introduced Ardex VR 95, a fast-track, one-component moisture vapor retarder specially designed for pressed-for-time new construction projects that have residual construction moisture up to 95% RH. These two systems cover almost every moisture problem that can be encountered on a project. They are very high quality, comply with existing ASTM standards and offer the highest level of protection.”
  • “Latest problem-solver products from Schönox are our EPA and EPA Rapid moisture mitigation systems,” said Tallman & Stowell. “These systems are aggressive solutions for handling even the most extreme moisture issues no matter the time schedule. Schönox EPA Rapid has the speed sufficient enough for the installation of resilient floor covering using our adhesive systems after only a few hours. With the speed and versatility of newer epoxy systems, we can meet the challenging demands we find in our daily fight on the job.”
  • “USG has tested several moisture mitigation systems to address moisture vapor and felt that a two-part, 100% solids epoxy system is the best solution,” added Kazienko. “USG Durock Brand RH-100 Moisture Vapor Reducer is designed to address up to 100% RH, as well as 25 pounds of moisture vapor emissions. More importantly, it can withstand alkalinity up to a pH of 14. It is a one-coat application that typically dries in four hours. It has a very low viscosity that promotes penetration into the concrete substrate and reduced strain on the installing contractor.”
  • “The Titebond 531 Plus Moisture Control System from Franklin International, including Titebond 531 Plus, cures in one and a half to two hours after application, enabling contractors to treat concrete subfloors in the morning and begin installing the flooring in two hours,” said Lamanno. “It cuts emission rates from most concrete subfloors by 75% to 90%, significantly reducing risk of mold and damage to flooring. It is fully warranted. This water-based epoxy contains no solvents or VOCs, so it is odor-free, nonflammable and noncombustible.”
  • “Dependable launched a new epoxy moisture mitigation system called Vaporseal HM (High Moisture) a few years ago,” said Keene. “Our epoxy system handles 100% relative humidity and 25 pound MVER. We can achieve this in either a 20 mil or 15 mil system, while staying cost-effective for our customers.”