Adhesives and mortars are arguably the most important components of any installation. Unless someone is looking for a true loose-lay installation, adhesives and mortars are absolutely required to make sure the floor (or wall) stays in place when exposed to traffic, temperature changes and other environmental stresses. We spoke with several adhesive and mortar manufacturers to find out more about chemical formulations, the different product types available, and what they recommend for certain installations.

Adhesives.According to Craig Morris, Ardex Americas technical services manager, the term “multipurpose” is a misnomer, as it implies that the adhesives can be used with a wide range of flooring. “This is not the case. Multipurpose may be used for traditional Action Bac carpet or felt-backed sheet goods, but it is not recommended for LVP/LVT, VCT, rubber flooring, fiberglass-backed sheet vinyl, carpet tile, wood, etc. Specialty adhesives are designed with specific floor coverings in mind. This is non-negotiable.”

The four basic types of flooring adhesives available today are SBR (styrene butadiene rubber), acrylic, epoxy and moisture-cured urethanes. SBR products are ideal for carpet and felt-backed sheet goods, as they provide a pressure-sensitive adhesive with good adhesion and tack. “These products are extremely versatile with strong initial grab and excellent bond integrity that can allow for repositioning and last-minute adjustments,” Morris said.

Acrylic adhesives are suited for vinyl planks, VCT, sheet vinyl and fiberglass-backed sheet products. Most are pressure-sensitive but some are wet-set. They also tend to be more expensive than SBRs, Morris noted. “Good ones offer superior moisture resistance and can be used over cutback adhesive residue.”

Epoxy adhesives are generally two-part adhesives that cure by a chemical process, resulting in a harder material that can resist point loads better than either SBR or acrylic. “This is ideal for application in hospital settings,” Morris stated. “A hospital room installation may call for an epoxy to be used where the bed or heavy rolling equipment will be. The rest of the floor will be done with acrylic.”

A moisture-cured urethane adhesive uses ambient moisture to cure, meaning installers don’t need to add water to it. This makes the product ideal for solid wood, engineered wood plank and wood parquet flooring, which are all sensitive to moisture, Morris said.

Depending on the type of flooring, contractors may opt for a releasable or a permanent adhesive. A releasable adhesive allows for replacement and repairing of part of the floor, such as popping out a damaged carpet tile. Broadloom, hardwoods and felt-backed goods need a permanent bond. “Some floor coverings require that aggressive grab that a wet-set, permanent installation gives you,” Morris said.

DriTac manufactures multi-use pressure-sensitive adhesives for use under a wide range of products including LVT, carpet tile, fiberglass-backed sheet vinyl, engineered wood and resilient flooring, as well as more specialized adhesive options. “Whether it is 4-In-1 sound and moisture control flooring adhesive/sealer combinations, or premium multi-use pressure sensitive flooring adhesives capable of installing several different floor coverings, these multi-faceted products allow end-users to positively impact their overall bottom line,” noted David Clarkson, DriTac vice president of marketing.

He added, “Generally, the industry has more than one technology suitable for every type of floor covering, offering the contractor and installer a wide variety of installation methods and pricing considerations.”

Premium multi-use pressure-sensitive products can be installed either via a wet-set (permanent) or dry-set (releasable) method, he added. “Wet or dry-set applications using the same adhesive provide flexibility, not only for their elastomeric qualities but may provide use for more than one installation option.”

Mark Lamanno, Franklin International technical market manager, said installers and contractors should always choose whatever adhesive the manufacturer recommends for the situation. “Adhesives in the vinyl and carpet world are designed for different applications. The same goes for wood. Some adhesives can be used to install all engineered wood flooring and some for solid wood planks.”

As far as new adhesive technology, Lamanno sees several advances. “We are seeing more three-in-ones for wood and some adhesive that has the capabilities to go above regular moisture recommendations for subfloors than is recommended by the flooring manufacturer.”

Ron Loffredo, H.B. Fuller senior area technical manager, said adhesive selection should be dependent on several factors, including the type of floor covering to be installed, the application process and the expected traffic.

“Acrylic copolymer latex can be formulated to provide strong bonds for vinyl flooring with excellent resistance to bond degradation by plasticizer migration and moisture at a moderate cost. Epoxies and polyurethanes can also be used with vinyl flooring and offer additional performance advantages.”

SBR products should never be used with solid vinyl due to plasticizer migration concerns, he added. “It is critical to read the adhesive label and technical data when selecting an adhesive as well as the flooring manufacturer’s recommendations, with particular focus on limitations and surface preparation.”

Loffredo said that vinyl tile and plank flooring should be installed with an adhesive that is initially tacky but transitions to a tough, cured bond. “This type of ‘transitional’ adhesive allows good bonds over non-porous substrates and the cured strength necessary to prevent gapping.”

MAPEI’s Jeff Johnson, Floor Covering Installation Systems business manager, said multipurpose adhesives are best used when “the installer is working with small installations of multiple product types and he or she is trying to keep the adhesive choices down to one.” However, they should not be used for vinyl or rubber installations because they can become compromised through plasticizer migration.

“Acrylics and epoxies are immune to plasticizer migration that comes when resilient flooring is placed in contact with adhesives.  Plasticizers are what make resilient flooring flexible. They also make SBR latex adhesives turn to soup,” he said.

When feasible, choose a specialized adhesive over a multipurpose one, he said, as they are can offer features and benefits that multipurpose may not. Johnson offers two examples: “Fast-tack carpet adhesives are designed to tack up and leg up quickly to hold carpet in place during the bonding process. Clear thin spread adhesives for VCT provide extended working times and are clear enough to see through to the layout lines.”

He recommends acrylic latex-type adhesives for solid vinyl and rubber sheet products over porous substrates. “For substrates that are non-porous, epoxy systems are best because they react together to create the adhesive bond, where latex systems need to lose water in order to function.”

As for wood flooring, nothing beats one-component urethane products, Johnson stated. “These types of products are single components that cure into a solid block of rubber. They typically contain no solvents and definitely no water.”

He said while some manufacturers describe their adhesives as transitional, that’s really just another way of saying “how an adhesive sets up more than a final bond condition. A transitional adhesive goes from a pressure-sensitive or releasable phase to a permanent bond phase over a period of time.” Vinyl tile, LVT and LVP are ideal for this type of adhesive, he adds. “They allow us to spread large areas of substrate with glue, allow it to tack up and install flooring without having wet glue ooze up between the pieces of flooring.”

Johnson sees two major trends in adhesive technologies today: De-contenting and performance enhancements to withstand higher moisture. “De-contenting is a word we use to describe reducing the content of an adhesive formulation due to cost constraints,” he explained. “If the sell price of a given product does not increase but the cost of raw materials do, adhesive manufacturers have no choice but to de-content their formulations in order to remain profitable.” He says the challenge is to de-content a product without changing its essential properties.

Ralph Richins, Q.E.P. Co. Inc. regional sales manager, also sees adhesive technology moving toward higher moisture levels. “We are now combining moisture barriers in the adhesive itself. It is applied with a special trowel to allow the moisture barrier to go to the substrate and the adhesive sits on top of it. We now find that slabs with 15 to 20 pounds of moisture are not that uncommon. The focus for adhesive technology will be on dealing with high moisture and pH levels.”

He noted that while most epoxy adhesives are two-part products, one-part products are also available. “A two part, where you mix part A with part B, is a little more difficult to work with as the window for open time is small. We now also have one-part epoxy in the bucket, ready to trowel.  Open times will vary with job site conditions. With use of either adhesive, the floor must be rolled with a 100lb roller.”

He added that choosing between a permanent or releasable adhesive will depend on the type of flooring and the conditions the flooring with face after it’s installed. “Pressure-sensitive adhesives are releasable when they are dry and sticky to the touch with no transfer of adhesive to the finger. If the flooring is installed while the adhesive is wet, the installation is a permanent one,” Richins added.

Mortars. Mark Pennine, Ardex Americas tile and stone specialist, said tile installers should choose highly modified thin-sets to set tiles including porcelain, glass and agglomerate constructions. “Non-porous tiles need a chemical bond from a highly modified mortar to achieve a well-bonded installation.”

For large-format tiles that are installed on a wall, a thin-set mortar with great sag resistance should be chosen. “Also, extended open time is a very important quality while installing these large tiles, especially if you’re making cuts around pipes, door jams and other complex areas as the material will stay fresh on the surface without skinning over.”

As for new technology, he sees more mortars being made that meet ANSI 118.15 for installing tile or stone in high-stress applications like pools, hot tubs, fountains and building facades. “Standard mortars that fall under ANSI 118.4 are sometimes just not strong enough for these types of jobs,” he said.

Tom Domenici, H.B. Fuller Construction Products senior area technical manager, breaks down mortars into the following categories: dry-set unmodified, modified (liquid or powder), epoxy and mastic/organic adhesives. Unmodified mortar are used to bond porous tile to porous substrates, such as under cement board and with some uncoupling systems. Polymer-modified are used for most tile and stone installations.

“A range of bond shear strengths, working characteristics and physical qualities differentiate products within the polymer-modified category,” he explained. “For example, large-format tile used on the floor of an open mall would require a fast-set, medium-bed mortar with high bond strength.”

Epoxy mortars are used to set moisture-sensitive stone or where high chemical resistance is required. Mastic/organic adhesives are primarily used for interior, vertical applications with more porous tile, he added.

Returning to the topic of large-format tile, Domenici recommends medium bed (especially for floors), non-sag (for wall applications) and a high bond strength. “Installers run into trouble when they use a regular modified thin-set mortar rather than a medium-bed mortar to install large-format tile,” he said. “The installer could leave for the night with a nice, flat floor, only to return the next morning to a floor with uneven corners and lippage. The mortar will have shrunk and pulled the large, heavy tile down.”

With so many choices of mortars and formulations available, it is essential for manufacturers to educate installers about the options, he added. “As installers become familiar with the widening variety of products, it is important that they follow the mortar mixing and installation instructions to get familiar with the products and achieve successful installations.”

Sean Boyle, Laticrete director of marketing and product management, said polymer-modified mortars are used the most widely for tile and stone installations, whereas unmodified mortars are typically used in “basic, lower-end, less traffic installations that are not deemed to be high use/crucial installations.”

Epoxies, on the other hand, are designed for moisture-sensitive stones like green marble or veneers that have resinous backings, as well as for use with difficult-to-bond substrates such as aluminum or steel. “Mastic-type adhesives are also available for common residential vertical installations of smaller veneers where a high level of performance is not required,” he added.

He sees mortar technologies moving in two directions: Products for large-format tile and products for reduced thickness tiles. “Due to the 3-5 mm thicknesses (of thin tiles), the flatter the floor the better to aid in reducing lippage and cracking due to uneven surfaces. The use of ANSI A118.5 level adhesives are essential to ensure bonding to the various reinforced backing materials, and more importantly providing a strong, reliable bedding layer to help eliminate cracking and withstand the installation’s required foot traffic level.”

Michael Venturelli, Q.E.P. Co. Inc. vp of sales, had this to say about mortars: “Depending on the body of the tile and stone, the majority of today’s installations will require polymer modified.  The theory is the denser the body, the more polymer is required to achieve a tenuous bond and keep the installation in service for its life expectancy.”

He added that along with these types of mortars, advancements are also occurring in epoxy mortars “for specific tile and stone applications, both horizontal and vertical.”