Flooring adhesives are an essential component of most types of installations. But what makes them function, why are some better than others in certain situations, and what are some of the latest technologies to help make the job easier? We spoke with a range of adhesive and mortar manufacturers to find out.

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Adhesive chemistries

Greg Wood, president of Advanced Adhesive Technologies (AAT), said adhesive chemistries are engineered to create specific benefits. “Each of the chemistries has unique characteristics: rigid bonds, fast cure times, moisture resistance, elasticity, cost advantages, longer working times, etc. It is critical that the flooring contractor have a trusted adhesive supplier that will provide advice for adhesive selection given the unique conditions of each job site.”

Larry Scott, DriTac vice president of field technical services, echoed those sentiments. “Each of the various technologies employed in flooring installations has its attributes and limitations for utilization. Factors that are often and readily considered include cost-effectiveness, ease of use and performance requirements.

“Generally speaking, waterborne chemistries tend to offer cost-effectiveness and ease of use, whereas reactive chemistries (polyurethane, epoxy) offer higher in-service performance. It is important to understand the in-service condition limitations of the floor covering being installed first and foremost in order to appropriately select an installation product that will meet both the expectations and requirements on the jobsite.”

Looking specifically at hardwood flooring adhesives, Mark Long, Stauf USA technical director, stated, “There are many different products and chemistries of wood flooring adhesives on the market today. They vary from MS (modified silane) to latex, urethane and solvents.”

He noted that each type has its advantages, and its tradeoffs. “MS products can be easy to work with but [generally] do not have the strength of some other adhesive types. Latex adhesives can also be easy to work with, but since they are made with water they can cause cupping issues.

“Urethane adhesives give you great bond strength, but can sometimes be harder to clean once dry. Solvent adhesives are very easy to work with in troweling and cleaning, with much greater strength. The downside is they will have a smell. However, that is only present in the short term.”

Tracy Muller, QEP adhesive product manager, breaks down the differences between adhesive chemistries this way: “100% solids polyurethane chemistry refers to the polymer chemistry of polyurethane being reacted (cross-linked) with polyol and isocyanate compounds. This forms a very rigid adhesive chemistry that is commonly used on bamboo, hardwood flooring and wide plank engineered flooring greater than five inches.

“Water-based latex adhesive chemistry is actually somewhat of a misnomer,” she added. “The water-based ‘latexes’ used for adhesives refer to synthetic polymers dispersed in a water solution—such as vinyl, acrylic, styrenated acrylics, polyvinyl alcohol, etc. These chemistries are often the most green and economically beneficial way of manufacturing adhesives. The broad base of adhesives you see in stores (such as multipurpose, carpet, vinyl, laminate, etc.) are all water-based latex chemistries.

Moving to epoxies, she noted, “Epoxide, or epoxy, adhesives come from a category of polymers which contain epoxy groups within their backbone structure. Through chemical reactions epoxies can be reacted (cross-linked) to form a very strong bond. These chemistries are used on extremely resilient substrates such as recycled rubber with thick backings, pure stainless steel or other smooth surfaces. Epoxide chemistry is also used to form true moisture vapor barriers on substrates that have moisture tables.”

Gary Liddington, W.F. Taylor business manager, manufacturer’s brands, stated, “Epoxies were traditionally used for severe service installation conditions because of their high strength and ability to cure between two non-porous substrates (such as a non-porous or sealed subfloor) and non-porous flooring (such as sheet goods).”

He added, “Latex products were originally introduced to replace solvent-borne adhesives and are still good adhesives. However, MS technology has become the chemistry of the future.”

Dave Darche, Bona US adhesives sales and market manager, said the moisture-curing and easy-cleanup properties of MS technology make it ideal for prefinished hardwood flooring. “With the lion’s share of new wood flooring installations being done with prefinished, the greater the urgency is to use adhesives that will not mar or chemically etch the prefinished surface.

“However, these adhesives are not lacking in shear strength. Several have very high psi ratings that rival and exceed those of urethanes, while also providing elongation that wood flooring installations benefit from due to the constant forces of shrinking and swelling. This is extremely helpful for all glue-assisted nail-down installations over 4 inches as well.”

Looking at epoxies in ceramic tile installation, Bostik’s Michelle Swiniarski, ceramic installation systems market manager, noted, “Epoxies have the reputation of being difficult to work with within the industry. There is a learning curve, but understanding the differences between working with a cementitious product and an epoxy can shorten this learning curve.

“Epoxies work by chemical reaction; cementitious grouts harden by crystallization. Epoxies are less affected by humidity and more affected by temperature. Once cured, they form an incredibly strong chemical bond to tiles and substrates. Therefore, it is extremely important to test the product with the tile being used to determine if your tile will require a grout release prior to application.”

She added, “Epoxy mortars have less elasticity and therefore are not recommended for exterior installations where there are extreme temperature swings which will cause rapid expansion and contraction. As a mortar, epoxies offer high performance in heavily trafficked areas and superb bonding performance. They are recommended for moisture-sensitive stones as they do not contribute any water to the system, which can cause cracking and curling in these types of tile. As a grout they offer superior resistance to chemicals and staining agents due to their low porosity and chemical composition.”

Steve Taylor, Custom Building Products’ director of technical and architectural marketing, said polymer-modified cement mortars are recommended for porcelain and natural stone tile. “The bond strength of non-modified mortars is weaker to these types of materials and we do not recommend them. For the best bond with additional crack isolation properties, Custom’s MegaLight is a strong option.”

Looking at other types of mortars, he added, “Latex-based or premixed mortars are easy to apply, but can be slow to dry in certain environments. Epoxy-based mortars, such as EBM-Lite, are more difficult to spread, but will not affect moisture-sensitive stone and cause warping of the tile.”

Texrite’s Alan Kin, sales/technical, broke down the different latex chemistries further. “Latex-polymer chemicals in mortars allow bonds over more substrates. Specialized latex-polymer mortars can now flex or move to resist minor movement via substrate deflection, as well as suppress minor cracks and/or minor vibrations.

“Use a higher premium (chemically-enhanced latex polymer) product for tile with increased density/hardness to addresses adhesion. Beyond just bond capabilities, the latex-polymer content creates an internal wrapping of cement and aggregate particles—they act as internal reinforcement while providing shielding for the cement hydration process. Look at these products as more than just a bond but the service condition once in place.”

Turning to epoxies, he stated, “Epoxy-resin mortars and grouts are gaining more usage based on chemical resistance bond characteristics, while also having very high stain resistance. They do not absorb liquids such as oil, grease, food spills, milk, juice or other common liquids/fluids. However, the epoxy resins do rely on the proper mixing ratio for proper hardening and curing.”


LVT/Resilient

Muller said the continued dominance of luxury vinyl tile and plank in the resilient segment has presented a few installation challenges. These include “increased moisture-related issues; an increased array of flooring, backings and compatible adhesives to choose from; and increased sound/acoustical specifications when choosing a compatible underlayment and adhesive.”

She said that Roberts 7350 Universal Vinyl Flooring Adhesive—which can be used with resilient options including LVT, solid vinyl tile, homogenous/heterogeneous flooring and VCT—helps alleviate these challenges. “This powerhouse pressure-sensitive adhesive has tremendous bond and shear strengths, plus it has excellent moisture and plasticizer migration resistance.”

Muller added that it is essential an installer does not use a different adhesive to install an underlayment to the subfloor than the one used to install the flooring. “The two different types of adhesives have different performance properties/characteristics and tend to achieve their full cure time at different rates. A contract-grade multipurpose adhesive (typically used to adhere an underlayment to a subfloor) contains more water than the typical pressure-sensitive adhesive used to install the flooring and will take longer to cure. This may also impact the dry time of the pressure-sensitive adhesive.”

Mark Lamanno, Franklin International technical market manager, recommends two adhesives for LVT: Titebond 670 Resilient Flooring Adhesive and Titebond 920 Acrylic Latex Flooring Adhesive.

Describing Titebond 670, he said, “Installers can apply this latex acrylic adhesive with either the wet lay or pressure sensitive methods, using a nap roller or small trowel. The adhesive sets quickly, accommodating tight remodeling and construction schedules. The acrylic polymer used in Titebond 670 resists plasticizer migration so it works well on all grades and types of LVT. It also gives the adhesive a stable tack profile over long periods of installation.”

Titebond 920, a pressure-sensitive adhesive that can be used to install vinyl composition tile and foam-backed hardwood parquet in high traffic areas, offers “a polymer formulation designed for extremely aggressive grab even when fully dry, eliminating edge curl on VCT and enabling quick installation and the return to high traffic immediately after installation. At the same time, the product offers a long open time of up to 72 hours for long installation jobs and tile repositionability. Over a prolonged period of time, the polymer loses some of the aggressive tack; holding flooring tightly in place while also allowing for easier removal of flooring down the road.”

Liddington spoke about Taylor Meta-Tec 2098 Premium Pressure Sensitive Adhesive. “Taylor 2098 is a multi-functional adhesive formulated to install luxury vinyl tile & plank, carpet tile, fiberglass backed sheet and sheet vinyl flooring. Taylor 2098 features a long working time and a strong but releasable bond.”

When working with the product, “as with all installations proper subfloor preparation is essential to ensure a good installation. One must also be careful to allow the Taylor 2098 to dry completely before installing the flooring if a releasable bond is desired. Floor installation into wet adhesive will generate a permanent, non-releasable bond.”

Scott explained the benefits of DriTac Eco-5900 MegaBond, a premium-grade, green resilient flooring adhesive specially formulated to help minimize vinyl plank shrinkage. “It is a high-performance, multifunctional flooring adhesive that provides maximum bond strength and high-caliber tack and peel strength. MegaBond offers high moisture resistance and shear strength with easy clean and easy spread formula characteristics.”

The product is designed for installing luxury vinyl tile and plank, vinyl sheet goods (heterogeneous/homogeneous), fiberglass backed sheet vinyl, carpet tile, rubber flooring, cork tile and cork/rubber/foam underlayments.


Ceramic Tile and Stone

The installation of large-format tile is, not surprisingly, the focus of most manufacturers’ latest mortars. However, since we’ll be covering large-format tile in greater depth in the April issue of FCI, we thought we’d briefly look at a few other ceramic tile and stone installation products.

MAPEI’s Brian Pistulka, tile and stone installation systems business manager, spoke about his company’s latest rollout, which includes three large-format tile installation products. We’ll cover the other two next month, but one of the newest products is Ultralite S1 Quick, a premium, rapid-setting, lightweight tile mortar with polymer.

“Ultralite S1 Quick is polymer-enriched for high performance and deformability; offers a nonsag formula for wall applications of large and heavy tile and stone; features nonslump characteristics for large-and-heavy tile and stone floor applications; can be used for thicker bond coats up to half an inch; and has a smooth and creamy consistency for easy handling and application,” he said.

Pistulka added this advice for working with tile installation products: “Follow manufacturers’ recommendations for the approved substrates, where to use, water mixing ratios, surface preparation, limitations and protection requirements.”

Swiniarski noted that Bostik EZPoxy EZClean 100% solids epoxy mortar and grout is “an innovative epoxy formulation making it easier to apply and clean off tile surfaces. It will exceed expectations as it glides across the tile surface and into the grout joint. When water is applied during the clean-up, it quickly releases for easy removal and joint dressing, then sets hard and solid.”

Taylor said Custom Building Products’ rapid-setting mortars like SpeedSet, MegaLite RS and ProLite RS “allow a fast return to service—typically with grouting in two to three hours.” He also stressed the importance of using the proper installation techniques. “Custom recently teamed up with the National Tile Contractors Association to produce a new educational video on troweling techniques called Trowel & Error. We encourage everyone to take a look by visiting https://youtu.be/Way5bMh-eYg.”

According to Kin, one of the biggest application errors when adding mortar to the back of a tile is “spot-bonding, also called the dab/dot method of application.” He said this method results in “limited and poor coverage to support the tiles. This type of application often breaks free due to a failure to trowel-in the adhesive to the bond surface. The adhesive mortar merely lays on the surface with no keying in or driving in with a trowel to achieve a good bond.”


Hardwood

Ron Loffredo, H.B. Fuller Construction Products technical advisor, said that Tec WoodPerfect Advanced Performance Wood Flooring Adhesive offers installers and contractors “fast initial grab with a creamy, 60-90 minute open time for quick placement without laboring over repositioning. WoodPerfect delivers one-step moisture control, strong initial grab, sound deadening and crack bridging capabilities in an installer-friendly, lightweight formula that’s easy to apply and easy to clean.

“It should be used with the Tec Moisture/Sound Inhibitor Trowel for moisture control and superior performance with less fatigue from handling. Tec LiquiDam EZ moisture vapor barrier should be used to treat concrete that’s greater than 95% RH before application of WoodPerfect.”

Lamanno recommends Titebond 771-Step Adhesive. “It combines the properties of a moisture-cure adhesive with the ability to be used as a moisture- and sound-control system, primarily for wood floor installations. Titebond now offers installers unlimited moisture control protection on 771-Step when used as both an adhesive and moisture-control system and applied as directed.

“Alternatively, installers also can use Titebond 771-Step as just a one-part adhesive simply by applying it with a different sized trowel. It can also be combined with Titebond 531 or Titebond 531 Plus Moisture Control Systems to achieve unlimited moisture protection. “

He added one note of caution when working in humid environments. “771-Step cures faster than urethane formulas do, so installers working in a humid environment need to ensure the flooring is installed in a timely manner (35 to 40 minutes).”

Sonny Callaham, Royal Adhesives & Sealants technical product manager, said the Parabond Adhesives division has just unveiled Millennium Series 3016 (MS 3016). “MS 3016 is a unique one-component wood floor adhesive based on modified silyl technology. It can bridge cracks up to 1/8” and will provide a powerful adhesive bond. MS 3016 contains zero VOCs and pre-installation moisture testing is not required. This adhesive contains no water, but cleans up as easy as an acrylic.”

Callaham noted the importance of reading all instructions before working with the product. “MS 3016 provides not only an adhesive, but unlimited moisture protection. To have the moisture protection a different trowel is required. Not only is the trowel selection important; the installer must understand the open and working time of the adhesive they are using. Some adhesives are designed to be used as a pressure sensitive, while this product is designed to be used as a wet-set adhesive.”

He added that reading the instructions is a good rule of thumb for any manufacturer and any job. “The most important step to ensure a successful installation is to read and understand the instructions found on the label and TDS—especially when using an ‘all-in-one’ system. Each manufacturer is going to have a specific set of guidelines for their products. Each will require different nuances to ensure their product works exactly how it was intended. The days of using all adhesive the same way is long gone and as contractors we need to be able to adapt.”

Scott, speaking about DriTac 7800 Supreme Green adhesive, agreed. “Using the proper trowel is vital for attaining success, regardless if the installation requires a bond only or multiple product installation attributes. Always refer to the specific installation guidelines on the pail label for trowel applicator requirements.”

Regarding DriTac 7800, he stated, “Supreme Green provides unlimited subfloor moisture control with no testing required and a lifetime warranty. This single-component, premium green sound and moisture control hybrid polymer wood flooring adhesive also acts as a crack suppressant.”

He also mentioned DriTac 7900 Super Grab, “a premium-grade urethane adhesive developed for installing long and wide plank wood flooring. Super Grab’s advanced formula provides installers with a permanent bond adhesive that offers excellent green grab and an option for controlling high levels of concrete moisture vapor emissions (up to 12 lb. CC and 85% RH). DriTac 7900 can be used to install multi-ply engineered plank, solid wood plank, bamboo flooring and more.”

Long said Stauf PUK-455 Wide Plank Adhesive “is the only adhesive developed specifically for the installation of solid planks without limitations on width, length or thickness over any suitable subfloor. Used to install wide, solid planks greater than seven inches, PUK-455 has a shear strength of over 680 psi and has been a choice for solid installation for many years in Germany. Now, with trends of the wide plank flooring in America, we brought our best single component to the American wood flooring installer base.”

Checking for moisture is important before using the product, he added. “Moisture content in concrete subfloors must be below three lbs. per 24 hours per 1,000 sq. ft. using the Calcium Chloride test or below 75% RH using an in-situ probe. If levels are greater than this it is recommended to use a Stauf sealer to protect the floor and have a successful installation. PUK-455 also has a special trowel, Stauf #17, especially designed to give you the best bond possible for solid flooring.”

Darche said his company recently unveiled Bona R859, a silane-based adhesive. “One performance factor quite apparent during a wood flooring installation with Bona R859 is its thicker viscosity. Silane-based adhesives in general are very easy to spread. For someone who has been troweling urethanes for decades it may raise a bit of a red flag. The thicker formulation of Bona R859 provides the feel that many professional installers are accustomed to and reduces the trepidation associated with an easier to spread adhesive product.

“Another key advantage is each pail contains a R859 MBP (Moisture Barrier Protection) Spacer Trowel allowing for the installation of engineered flooring up to 16-inch widths or solid plank flooring up to nine-inch widths. The MBP Clip-On Trowel attaches to a standard trowel and applies a moisture barrier of protection along with maximum ridge stability.”

He had this to say about open times: “Today’s adhesives, whether they are urethane or silane, are installed in a wet lay manner. Generally speaking, the longer the open time the longer it will take the installed flooring to reach full cure. If there are no concerns that boards may get shifted out of place from light foot traffic during the installation time frame, then an adhesive with a longer open time will be suited for that application. If the flooring will be subjected to normal foot traffic during the installation period—or the flooring needs to be sanded and finished soon after completion—than an adhesive with a shorter open time will be better-suited for that application.”


Carpet

Wood mentioned the reengineered AAT-295 Ultra Premium Carpet Adhesive, which “offers a much faster drying adhesive. The most important feature of the enhanced formula is its ability to be used over slabs with an in situ RH of 95%. Our 295 can be used for direct glue-down installations of virtually all broadloom carpet backings and is especially recommended for high-performance carpet backings.”

He added not to neglect the basics. “As each adhesive manufacturer would recommend, be sure the subfloor testing (MVER, in situ RH and pH) is performed properly, under the correct conditions and in the specified quantities. Use the correct trowel and the proper three-section roller. These things always impact the application and long-term performance of any floor covering installation. The details of subfloor prep and adhesive selection are key aspects of any successful flooring installation.”