Concrete Moisture: The impacts of fast-track construction and flooring preferences - Aug/Sep 19

By Beth Miller

As concrete moisture issues persist in both new construction and existing slabs, floor prep suppliers must work to find solutions in response to the evolution of floorcovering and adhesive products, which have varying tolerances for moisture in a slab. But, for floor prep suppliers, the only way around is through, so they continue to evolve their products based on the needs of a highly demanding construction industry.

Moisture issues may relate to too much water in the mix (water of convenience) in the case of new slabs, lack of a vapor barrier in the case of an existing slab, fluctuating weather conditions, hard-troweled concrete or finally, fast-track construction, which runs at the top of the list of every floor prep supplier interviewed for this article.

“Fast-track construction timetables are now the rule and not the exception, and the move to more environmentally friendly adhesive formulations and impervious floorcoverings has caused ‘the perfect storm’ of moisture-related flooring failures,” says Drew Jubis, technical sales representative with Uzin Utz North America.

MOISTURE ISSUES: NEW VERSUS OLD
Remediating moisture issues in both old and new slabs is not an exact science. The variables that are factored into moisture mitigation are numerous and varied, and they continue to keep floor prep suppliers on their toes when it comes to developing new products or modifying old ones to keep up with an evolving market.

In the case of new construction, the conversation centers around excess water of convenience used to mix concrete and make it pourable; if it is too wet, it slows down the drying process. The additional water in the mix makes the concrete easier to work and go down faster, but it requires more drying time. According to Aaron Abbott, senior technical project manager with Laticrete, “It can take up to six months or more to reach the conditions required to install floorcoverings.” And with modern construction methods getting faster with more emphasis being placed on fast-track projects, “all of this is pushing the envelope on floorcovering adhesives and floorcovering products themselves to be able to go down on concrete that is still evaporating its moisture,” says Abbott.

Moisture issues are not limited to wet areas of the country either. “We see moisture issues across the country,” says Chris Forgey, business director of specialty flooring with GCP Applied Technologies. “You can have a moisture issue in the desert.”

Another problem is hard-troweled concrete, which limits the water vapor passing through the slab, causing greater challenges once the building is buttoned up and the HVAC system is turned on. The ambient air pulls the moisture to the surface, attacking the glue under the floorcovering, which is the result of contractors installing the flooring before the room or building is acclimated.

Renovations come with their own set of moisture issues. For existing slabs on or below grade, the presence of a vapor barrier is an unknown. And if it is known that a vapor barrier was used, whether or not it is intact is an uncertainty. Ron Loffredo, senior technical advisor for H.B. Fuller, says, “Plastic vapor barriers on slab degrade in ten to 12 years.” In addition, lingering problems from the new build can still exist. Leaky pipes, ground moisture and damaged roofing can all contribute to moisture issues in renovation.

Slab thickness is another factor to consider when discussing moisture. Is it a 4”, 6” or 12” slab? According to Seth Pevarnik, director of technical service with Ardex Americas, drying time for a 4” slab could be three months. “With a 12” slab on some of these hospital projects, it’s one-and-a-half years, and you’re still seeing higher readings than normal,” says Pevarnik.

Finally, what floorcovering product is going on top? Is it a permeable surface like broadloom or a non-permeable surface like rubber, sheet vinyl or even hard-backed carpet tile? With the popularity of resilient flooring picking up speed, permeable flooring products are being replaced with products that won’t let moisture pass through-which results in mold and mildew growth at the subfloor level and contributes to the breakdown of both adhesives and self-levelers.

These issues can be prevented by proper testing and proper time allowance for acclimatization, curing and drying. But sufficient time is not often an option.

TEST METHOD UPDATE
Recommendations from the floorcovering and the adhesive manufacturers, depending on the flooring type, should be followed. At least one if not both test methods for relative humidity, (RH) ASTM F2170 and calcium chloride ASTM F1869, will be recommended. According to Loffredo, the RH test measures the RH within the slab itself while the calcium chloride test measures the moisture vapor emitted from the slab at the time of the test.

Uzin Utz, a German producer of mostly cementitious products, recommends in-situ RH probes to test for water vapor based on the ASTM E96 and ASTM F3010 standards. ASTM F3010 is described as “standard practice for two-component, resin-based, membrane-forming moisture mitigation systems for use under resilient floorcoverings.”

Testing for pH is another matter. Measuring the pH in a slab is a good indicator of future problems if the reading is in excess of 12. According to Jeff Johnson, Mapei business manager for floorcovering installation systems, “You need to understand that fresh concrete almost always has a high pH until the surface gets a chance to carbonate and reach a more normal level of nine to 11.

GET ON THE FAST TRACK
Fast-track construction is reported to be the top cause of moisture issues in floorcovering. With continuously shrinking construction timelines, floor prep products are being modified to accept higher RH values. As tolerances rise, the question of whether or not these products are viable looms.
Traditionally, two-part (resin and a hardener) epoxies have been the go-to moisture mitigation solution; however, there are new hybrid products that are only one-part, saving time and money. For example, H.B. Fuller offers both an epoxy and a hybrid. Its Tec LiquiDam epoxy was developed in the 1960s and was primarily used under terrazzo. The two-part, single-coat product has since undergone some slight modifications, like the addition of color to indicate coverage as it’s being poured, but its chemical makeup has remained intact. The newest product, Tec LiquiDam EZ, was launched in 2016 and is a one-part, two-coat product. The products are roughly equal in cost depending on the size of the project and both are designed for 100% RH. Tec LiquiDam epoxy requires five-and-a-half hours versus EZ’s three hours.

According to Loffredo, “Everyone wants the next generation hybrid product. It’s cleaner, user-friendly and environmentally friendly.” But despite the demand for the hybrid products, Loffredo believes the epoxies still have the edge “because they’ve been out there forever.”

Laticrete offers its Vapor Ban Primer ER that is a single-coat, two-part, rapid-setting epoxy, launched in Q1 2019 in response to the fast-paced needs of the construction industry. It meets the ASTM F3010 standard and is designed to take a two-day installation down to one. It is ready for a self-leveling underlayment in three to four hours versus 12 to 16 hours. No additional primer is needed.

While many products in the market offer protection against moisture up to 100% RH, there are others that don’t go quite as high. And though one might expect these products to have been rendered obsolete by their superior counterparts, that’s not the case. According to interviewees, the products are recommended based on need. So, a product that goes to 98% RH is designed for an environment, typically new construction, where the RH already tests below 100% and is expected to continue decreasing. These products are generally more affordable than the premium-priced 100% RH products. Ardex’s VR98 is designed for above-grade new construction and allows up to 98% RH in the slab. According to Ardex’s Pevarnik, “Products with a max RH of less than 100% should not be used on slabs on-grade or below-grade, like in the case of a renovation, because you can’t confirm if you have an intact vapor retarder.”

An example of a 100% RH one-coat epoxy is Ardex’s MC Rapid product. No testing is required. MC Rapid can be applied to below-grade or on-grade slabs in a renovation. It has been around for approximately ten years and replaced Ardex’s previous two-coat epoxies, saving time and money.

Schönox’s EPA epoxy requires four to six hours cure time versus the firm’s EPA Rapid’s two to three hours. After EPA Rapid has cured, the slab is ready for Schönox’s SHP Primer that can be applied directly. Total time from surface profile to skim-leveling for the EPA Rapid equals three to four hours. Rapid is ideal for renovations where mitigation and flooring installation need to happen in the same day, according to Shane Jenkins, senior technical director of HPS Schönox. Once either of these products are applied, no testing is required; they allow up to 100% RH.

Jenkins contends that epoxy is the only product viewed as a true solution. He adds, “Sheet barriers are recognized, but it depends on the manufacturer of the flooring and what they recognize as an acceptable solution to the moisture problem.” According to Loffredo, the reason for choosing a sheet barrier is that some don’t want to use a liquid membrane; however, moisture can get trapped between a sheet barrier and the floor, promoting mold and mildew.

Ron Sandoval, director of technical with XL North Chemical Company, affirms that, “Looselay membranes are for soft good application use only because most resilient floors can’t accept a sheet barrier.” However, there are plenty of products out there that are designed to do the job.

Sheet barrier products like Kovara (formerly VersaShield) offer 99.5% RH and are designed to be applied directly to the slab, with the adhesive applied on top for the floorcovering installation. Kovara lasts the lifetime of the floorcovering and is specified for all commercial applications. The advantage to this type of barrier is the speed with which it can applied, allowing for a floorcovering installation to occur overnight, reducing down-time. GCP has recently introduced a self-adhered version of its sheet moisture barrier, Kovara AB300, which speeds up the application even further.

MAKING THE SWITCH
In the late 1980s, environmental regulations required lower VOCs in adhesives, causing the switch from solvent-based to water-based adhesives. The first generation did not react well to high moisture and high pH conditions in slabs and would deteriorate, causing flooring failures. Additionally, the move from breathable floorcoverings to impervious products like resilient and carpet tile contributed to the switch in adhesive technology. And the changes in adhesives and floorcovering remedied some issues but caused others.

According to Loffredo, the water-based adhesives offered today are even stronger than those that are solvent-based. When water-based adhesives were first introduced, there was a learning curve involved in trying to make a water-based adhesive perform like a solvent-based adhesive.

While the majority of interviewees feel that water-based adhesives have superseded their predecessors, Jenkins says, “Prior to ’92, we had more asphaltic-based adhesives. It acted like a moisture mitigation [system] in itself. Today, water-based adhesives are more susceptible to excess water in concrete.”

Karen Bellinger, partner at HPS Schönox business development, points out why many feel that the new water-based adhesives are superior to the solvent-based. “The reason you may be hearing that is some of these new adhesives are now allowing moisture to go up to a higher percentage. In the past, they would only go up to 75% RH, and now, we’re getting better performing technology with water-based adhesives that allow you to go up to a higher RH that isn’t going to suppress the moisture, but it will allow the glue to stay intact.”

Mapei’s Johnson weighs in on the solvent-based versus water-based adhesives, saying, “Believe it or not, solvent-based adhesives had moisture-related problems as well. The switch from solvent-based to water-based adhesives is not the problem. The problem is the compression of timelines to get the work done. This means that adhesives are being applied to substandard concrete substrates, and that is where you get into trouble.”

Loffredo points out that the old asbestos tile that was used over cut-back glue was breathable. “No one tested for moisture because the old stuff breathed,” he says. Due to this breathability, there were no signs of a moisture issue. However, once the new products were installed, moisture was trapped underneath and attacked the glue. A failure occurred, but not for the reasons contractors and installers believed. According to Loffredo, when he would explain that the floorcovering had changed and that the adhesive was not to blame, the response was disbelief.

Concerning the change in floorcovering permeability, GCP’s Forgey says, “[Flooring manufacturers] are looking at it from a different perspective. They’re looking at it from the top down. They are trying to keep moisture from penetrating their product. When you’re talking about mitigation though, you’re actually talking about something that will protect the finished floor and the adhesive from the vapor and increased alkalinity. When you talk about a high-moisture adhesive, that’s not going to protect the finished flooring or block any of those salts, so you can still get salt deposits.”

This is where the floor prep suppliers have had to step up and embrace the new challenges. Forgey says, “We are the company that helps solve issues. [Flooring manufacturers] are doing what they should be doing to sell more flooring. It’s our challenge to help it be installed correctly.”

EDUCATION
Some within the floor prep supplier community feel that the conversation concerning moisture mitigation is being addressed on the front-end by flooring contractors, architects, general contractors and end-users. But more education is needed.

“Concrete is a mixed bag of issues,” says Johnson. “It has a bunch of water in it to begin with. It curls and cracks during drying. It may never truly dry unless you expose it to a negative humidity condition-under HVAC where the ambient air is dryer then the humidity in the slab.”
Uzin’s Jubis says, “Yes, these professionals are being more proactive, and sadly in some cases due to a past floorcovering failure.”

Forgey adds, “The discussions [concerning moisture mitigation] vary quite a bit, depending on whether we are talking to an architect, a [general contractor], a flooring installer, which stage the project is in and whether it’s a renovation or new construction…but architects are listening to us more and more.”

Uzin works directly with architects, general contractors, flooring contractors and specifiers. Discussions take place daily concerning “the need to assess every project for its potential need for moisture mitigation and offer a solution based on what is required for each project,” says Jubis. For instance, its PE 414 works in moisture up to 95% RH and is designed for new construction above-grade when drying time is problematic. Then there’s the PE 460 two-part epoxy that mitigates moisture vapor up to 100% RH, which could certainly work in a renovation where the presence of a vapor barrier is questionable. So, there are decisions that must be made on the front-end to determine which products are suitable for each project.

Mapei offers training throughout the U.S. and Canada via its Mapei Technical Institute, where topics like moisture mitigation techniques are discussed, as well as products like its Mapecontact MRT designed for resilient, Ultrabond ECO 995 for wood flooring and Planiseal products, which are moisture barriers designed for use with a primer, a leveling compound followed by the flooring. Mapei has a team of architectural sales reps that work with the architectural community, training them on moisture mitigation and self-leveling underlayments. It is involved in multiple trade associations where contractors are exposed to moisture mitigation benefits. And, finally, it has a specialized team of sales personnel whose responsibility it is to work with commercial flooring contractors to discuss the benefits of Mapei’s moisture mitigation products.

Laticrete University is an online program that offers self-directed courses on product information and industry standards. It is free to sign up and is available to anyone. Laticrete also works directly with architects, specifiers and contractors and offers live demos at trade shows as well as videos and other instructional material via social media.

Prior to offering CEUs, Schönox spoke with the architect community regularly, and out of that conversation came the credits. In its second year, the CEU courses were designed to encourage proactive moisture mitigation on the front-end and help save money in the long run. Schönox is seeing architects write moisture mitigation into the specifications now.

Ardex has six training centers in the U.S. and Canada that service approximately 8,000 contractors each year. Courses range from underlayments to moisture control to polished concrete systems. It offers 120 field reps who speak with architects and contractors and it also holds external and internal training for sales professionals.



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