Concrete moisture testing is key to avoiding an installation failure; however, many contractors and installers still roll the dice on whether they test a jobsite or not. We spoke with concrete moisture testing experts about their latest products, why concrete moisture testing is essential and how skipping important tests can negatively affect contractors in the long-run.

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Reasons for moisture

Excess levels of moisture in concrete don’t just stem from a single issue, but many, which range across the board. Mark Lamanno, technical market manager, Franklin International (Titebond), listed a number of common sources known to create excess moisture.

“The slab could still be moist because it has not fully cured and dried,” he explained. “Most concrete slabs for housing are 4” thick. They can take up to 150 days to cure and dry—that’s 30 days to cure and up to 120 more days to fully dry. It’s also possible that piping in the slabs has broken and is leaking moisture into the concrete.”

Lamanno suggested the barrier between the soil and the slab might also have been compromised—possibly torn during the pour or otherwise damaged. “Changes in grade, or pouring the slab below grade, can subject the slab to more groundwater. Moisture issues cause 95% of the problems with wood flooring installations.”

Grete Heimerdinger, product manager, Lignomat USA, noted additional reasons for high moisture, such as freshly poured concrete that isn’t yet cured, as well as water spills. “Moisture infiltrations from walls that aren’t sealed properly, and ground-level infiltration from a defective or non-existent vapor barrier are also common causes of excess moisture.”

Alfred Melka, general manager, Loba-Wakol, pointed out that with new concrete most issues derive from a combination of overwatering and lack of sufficient dry time. “In existing concrete, it can be a variety of causes from lack of a moisture membrane to broken pipes, roof leaks, hydrostatic pressure, etc.”

Dan Marvin, director of technical services, MAPEI, stated moisture levels in concrete are a concern for all flooring installations, but especially those for moisture-sensitive finishes like wood, bamboo and vinyl. “Moisture in concrete can come from the mix itself (green concrete that has not yet had time to dry below the limits of the flooring) or from external sources if a moisture barrier is not in place and functioning under the slab.”

J. Alex Keene, product development, Keene Building Products and Dependable LLC, said excess moisture typically comes from moisture in the ground or from the environment during installation. “This is typically caused by a failure of the below-slab moisture vapor management system or by the lack of a system entirely. Excessive moisture also exists when a concrete slab is reintroduced to moisture after it is poured.

Tom Laurenzi, president, Delmhorst Instrument Co., mentioned how in elevated slabs, the only source is the residual moisture left from the original concrete mix. “So the drying rate is important and the factors that affect the rate are mostly the ambient temperature and RH, the curing method and the water-to-cement ratio.”

Effects of excessive moisture

“Excess moisture in concrete can cause flooring failures including delamination of flooring goods, blistering, bumps, curling, blushing, efflorescence, mold, mildew, etc., resulting in extremely expensive repairs and delays,” remarked Dean Cunningham, associate technical service manager, specialty product division, Laticrete.

Mark Long, technical director, Stauf USA, indicated a few more unpleasant effects that can occur. “A couple of issues causing floor failure are expansion and cupping of flooring, adhesive dissolving, bubbled flooring and the creation of mold and mildew, which causes an environmental concern.”

Hubert Steinberg, manager of export and industry, Schönox GmbH, added, “Typical failures include bubbles under resilient flooring, blistering with coatings/sealers, discoloration of flooring due to contaminants affecting flooring from underneath, flooring tiles and planks starting to peak due to expansion, dramatic expansion of hardwood floors resulting in bond break, and moisture-sensitive installation products such as adhesives, patches, etc., beginning to fail and/or fall apart.”

Penny Czarra, president and director, AC•Tech, shared what she calls a “spoiler alert” of what causes the most damage. She says it’s not the moisture content in concrete itself that leads to frequent failures in flooring installations. “It’s the pH—the alkaline salts that the vapor molecules carry with them to the bond interface as moisture vapor equalizes throughout the concrete slab and toward the surface—over time.”

In-situ probe vs. calcium chloride testing

One of the most common questions regarding concrete moisture testing is which ASTM test to perform—F1869 (calcium chloride) or F2170 (in-situ probe).

“It is always preferable to perform a combination of tests for a more complete understanding of the moisture conditions of the concrete slab,” expressed Andrew Rynhart, CEO, Tramex. “We recommend a combination of ASTM F2659 non-destructive impedance testing and ASTM F2170 in-situ testing along with monitoring the ambient conditions and surface temperature of the slab. The non-destructive F2659 impedance tests will give a precise evaluation of the moisture conditions of the upper 1” of the slab.”

Rynhart illustrated how a moisture map of the entire floor can be rapidly built up and used as a guideline to help determine when and where to position the F2170 relative humidity tests. “By comparing the moisture map with the on-site ambient relative humidity readings and surface temperature, it is possible to separate dew point/condensation issues from other potential moisture problems and deal with them separately. Data from a single test can give misleading information, which can lead to floor failure or over-specification of mitigation.”

Marvin pointed out that both tests have their advocates. “In-situ tests are designed to quantify how much moisture is present within the concrete. Calcium chloride tests are designed to quantify how much moisture is moving through the slab. Most manufacturers reference both when trying to give an idea of ‘how much is too much.’ The important thing is to have a comfort level with how the test is run and how the results are interpreted.”

According to Melka, both methods are approved as quantitative tests; however, concrete types and composition are changing so “in-situ probes are to be preferred because they are not affected by new concrete types and mixtures.”

Heimerdinger suggested the in-situ probe test, because the excess moisture can be detected and the proper vapor barrier can be installed to prevent future floor covering failures. “However, as a general guideline, it is always best to follow the manufacturers’ instructions.”

The calcium chloride test does provide useful information but since it is affected only by the moisture condition at 1/2” to 3/4” below the surface, it does not provide all the information necessary to make a determination if the slab is ready, stated Czarra.

“This test cannot tell if moisture migration exists and if there is moisture present deeper in the slab,” she noted. “This is the case with virtually all of the traditional surface tests that the industry has been using for decades. This also includes handheld moisture meters, which are great tools for comparative testing and determining locations of high moisture” but should not be considered tools for quantitative testing.

Cunningham emphasized that while there are many schools of thought on which ASTM moisture test is appropriate for flooring, it is ultimately the flooring and adhesive manufacturer who must specify the test method and the maximum moisture level.

“However, in the absence of the manufacturers’ recommendation and requirements, it is best to use a combination of test methods in order to have a better understanding of the current moisture conditions in a slab,” he said. “More moisture information and data from multiple methods allows for better, more informed decisions as to how best to proceed and achieve a successful installation.”

Testing advice for contractors

Long stressed that when people hire a contractor to do the work, they want it done the proper way. “Why not start off right and do the required test? If you don’t test, one day it will come back to [bite] you, somewhere and at some time. No one wins when there is a floor failure, especially from not doing what is required.”

Rynhart said when a calculated risk goes wrong the contractor is on their own. “There are many experts in the industry who can understand the results of the different tests and when called upon can assist with identifying the cause of most problems. However, if you don’t test at all then you’re running the risk of being deemed the cause of the problem, and with considerable justification.”

Steinberg stated ASTM and manufacturers specify for a reason. “Rolling the dice means to take over all responsibility. There are a lot of solutions out there to handle moisture accordingly, which then transfers the liability to the manufacturer of these systems—so why take that huge risk?”

Most floor covering and moisture management systems warranties require a moisture test for validity, Keene added. “Further, without a moisture test it is impossible to make an informed decision as to how to treat a moisture problem if it exists. Moisture is the most litigated issue in construction. Testing and managing moisture problems saves contractors a lot of money and time, while also mitigating the risk of flooring failure.”

Heimerdinger’s advice for contractors is short and to the point. “I would say: Consider how much the floor installation costs, including materials and labor, and also consider what a failure will do to your reputation.”

Laurenzi has seen estimates of moisture-related flooring losses in the U.S. reaching $1 billion annually, and has a hard time understanding why someone would risk their reputation and major financial loss by not testing for moisture.

“It’s not even ok to say some test is better than no test. It is critical for the contractor to understand not only the characteristics and perhaps limitations of the flooring and adhesive products, but as much as possible about the overall construction design—from the ground up,” he stated. “With this knowledge, and a good grasp of the nuances of in-situ testing, a contractor can best interpret and understand results for the best decision-making.”

While there are ‘hot-spots’ in the U.S. for moisture issues, they can occur virtually anywhere, added Marvin. “Just because an installer hasn’t experienced a moisture issue yet doesn’t mean that one isn’t looming.”

Latest products

“Titebond offers two proven products for protecting wood flooring from subfloor moisture,” assured Lamanno. “Titebond 531 Plus, a moisture-control system; and Titebond 771-Step, our all-in-one adhesive and moisture control product. Both are advanced formulations developed for ease of application, superior performance and environmental safety.”

According to Steinberg, Schonox has a variety of products to handle moisture. “Schonox offers moisture mitigation systems handling any level of residual moisture in concrete, a problem solver over new, damp concrete, and moisture-resistant floor preparation products (patches, self-leveling compounds, adhesives, etc.).”

Laurenzi mentioned two packages for concrete testing—both of which are ASTM F2170 compliant. “Total Check is a multi-function moisture meter and thermo-hygrometer with data collection capability. HT-4000F is a stand-alone thermo-hygrometer that provides an economical means of measuring concrete. Both are robust and reliable tools that will provide very low cost per test results.”

Rynhart said, “The Tramex Flooring Inspection Kit combines all the tools needed to monitor the ambient conditions of the environment; perform instant, non-destructive impedance testing per ASTM F2659; and perform relative humidity testing per ASTM 2170 with the Tramex reusable Hygro-i RH probes.”

AC•Tech manufactures and supports a full line of ASTM F3010 epoxy primers specifically engineered for moisture and alkalinity control under resilient flooring, noted Czarra. “AC•Tech Substrate Sleuths is a free technical best practices support service for flooring mechanics and contractors.”

Keene said Dependable offers two excellent moisture management systems. “For everyday moisture control, we offer the field-tested Cutdown II—a latex-based moisture mitigation system, requiring almost no surface preparation that can handle up to 90% relative humidity.

“Vaporseal HM is our two-part epoxy moisture system. Vaporseal is mixed with a 1:1 mix ratio, something no other product on the market offers, contains almost no odor and is made with no VOCs.”

According to Long, Stauf has a variety of moisture control products from sealer/primers to adhesives that are all equipped with high moisture barriers. “Our moisture control products are as follows: ERP-270 Perma-Seal Epoxy-Based Sealer, ACS-210 True-Seal Acrylic Concrete Sealer/Primer, VPU-155 “S” Urethane Sealer, SMP-940 Superior Polymer-Based Wood Flooring Adhesive, PUM-950 Power-Mastic Urethane-Based Wood Flooring Adhesive, and lastly, SMP-960 One-Step Polymer-Based Wood Flooring Adhesive.”

Cunningham discussed two products: Laticrete’s NXT Vapor Reduction Coating and Drytek’s Moisture Vapor Barrier. “Both products are single-coat, 100% solids, liquid-applied, two-part epoxy coatings specifically designed for controlling the moisture vapor emission rate from new or existing concrete slabs prior to installing.”

According to Marvin, MAPEI offers a variety of moisture control options for floors. “Our ECO 995 product is designed to both control moisture and adhere wood flooring when used with the special trowel clip we include in the bucket. For large areas with potential moisture issues, our Planiseal VS epoxy moisture reduction barrier is cheap insurance when compared to a flooring failure. We also offer sheet membrane options.”

Melka talked about a Loba-Wakol product called Wakol PU 280. “It’s a single-component roll-on moisture barrier that is considered revolutionary because it doesn’t require extensive slab prep and it cures in less than one hour.”