Adhesive Q&A

Christopher Capobianco

Having been in floor covering for 40 years now, I’ve asked my share of questions about adhesives and in the last 26 years on the wholesale side, have also been asked a lot of those questions. Here are a few common ones.

Q: Is there anything better than standard urethane adhesive for wood floors?

A: I recently attended a seminar on wood floor adhesive and was interested to learn about some new technology. The urethane adhesive that has been the standard for glue-down wood floors (and some rubber floors too, as we will discuss later) is still extremely popular and works well.

The advantages are familiarity by many installers, and great bond strength for most applications. The drawback is that if the adhesive gets on the surface of the flooring, it can be difficult to completely remove when wet and impossible to remove once cured. The other main disadvantage is that it is very thick and hard to spread. New technology in adhesive for wood flooring includes products that are easier to spread and clean up, and some that have built-in acoustic insulation characteristics that avoid the need for a separate underlayment.

There are also products that have very high resistance to concrete moisture issues and don’t even require that you test the concrete. That last one is a pretty big deal, considering how much fast track construction is going on that require floors to be installed long before the concrete is fully dried.

Q: Do I really have to use the manufacturer-label adhesive or can I use something less expensive? Will it work just as well?

A: Prior to 1992 I was the guy asking that question quite often during the years that I worked in my family’s retail floor covering store. I especially remember in the 1980s when the first “solvent-free” adhesives were coming out and I really wanted to try some of them for environmental reasons. I worried about warranty issues, had a good conversation with my distributor rep at the time and started using these adhesives under certain flooring products. He assured me that the risk is low and the adhesive manufacturer would back it up. We had good success with the adhesives we used for VCT and carpet, and the rest is history, you could say, as the industry is virtually all solvent-free now.

Since then, I have been on the manufacturer side both in sales and support, and those questions continue to come up when someone wants to save money or is in a jam because they don’t have enough adhesive to finish the job. I have several thoughts on the subject. Having worked in technical support for manufacturers of resilient floor coverings, I’ve seen firsthand the research that goes into a lot of manufacturer-branded adhesives.

The first priorities we always had when researching new ones was that it would work well with the floor covering product, be easy for the installer to use and give the flooring manufacturer the level of confidence so they could offer a warranty. From the sales side, adhesives are obviously a profit centre for the flooring manufacturer, but they also give the best assurance of a successful installation for everyone.

Adhesive selection is critical. In this photo, VCT adhesive was used under vinyl-back LVT, leading to curling tile.

All that said, I almost always recommend the manufacturer’s adhesive. The cost savings to switch on most jobs is not enough to make a big difference, and I’d bet the customer would not mind paying a bit more for the extra assurance that the floor covering and the adhesive are from a single source with a warranty. However, I understand that any type of cost savings on large projects can be the difference between being awarded the job or not.

Sometimes you can negotiate with the flooring manufacturer to reduce their adhesive price on large orders. Otherwise, if you look for alternates, there are several things to keep in mind. Common wisdom is that for more “generic” installations like “action-back” carpet, vinyl composition tile, and vinyl plank or other so-called “LVT”, a good quality adhesive by a reliable manufacturer specifically recommend for the floor covering you are installing is a safe bet.

With regard to “specialty” resilient floor coverings on the market, such as most sheet vinyls, “PVC-Free” tile and plank and rubber, I would never risk a switch. These high cost products often have special adhesive requirements. The same holds true for certain carpets, as has been the case my whole career. Carpets with specialized backings that offer warranties for tuft bind and wear require a specific adhesive, part of the installation system and thus the warranty.

Q: With all the vinyl floors out there today, how can I simplify my adhesive inventory?

A: As far as vinyls, I said earlier that I’m not as worried about products like VCT and most LVT from an adhesive point of view so it’s possible to keep one adhesive in stock for each of these product categories. Use something good quality that’s specifically recommended for the floor covering you are installing. However, there are three important points to add.

One, VCT adhesive is NOT recommended on vinyl back products like LVT so don’t make that mistake. It may stick initially but over the long term, probably not.

Two, there are a lot of large-format vinyl-tile products on the market today and those worry me when it comes to possible shrinkage. Vinyl tends to expand and contract slightly with temperature swings, so a firm setting adhesive is important.

Three, adhesive open time is not the same for all products. VCT adhesives are pressure sensitive; they can be allowed to completely dry to the touch and “tack up.” This allows the installer to spread large areas of adhesive at once and work on top of the

flooring right after it is set into adhesive. However, LVT and sheet vinyl adhesives may not always be used in this same way. The strongest bond is with adhesive slightly wet at the time flooring is set. These adhesives are not allowed to completely dry. When ready, a touch to the adhesive will show the lines from the trowel ridges. Another option with products like homogeneous solid vinyl is a “wet set” installation. This takes a lot more time and the installer can’t work on top of the floor.

Q: What do you recommend for rubber floors?

A: Rubber flooring may be the category with more different adhesive options than any other, from standard acrylic to a two-part epoxy and even pressure sensitive “releasable” in some cases. There are many different types of material in the rubber category, so adhesive selection is very product-specific.

Traditional rubber is installed in most applications with a single-part adhesive that’s similar in its use to other resilient adhesives, but not the same chemically. Floors subjected to very high traffic, rolling loads, or topical moisture might be installed with a reactive such as a two-part epoxy or polyurethane. Make sure you know which of these two options is right for the job, as the cost of adhesive and labor is very different for these two options.

“Recycled” rubber (also known as “crumb” or “composition” rubber) is used in a lot of fitness applications, typically as 8 mm thick rolls or tile with large percentage of black recycled rubber content. Thinner versions of recycled rubber and rubber-cork products generally have a higher colour content that are typically 3.2 to 4 mm thick and are used for a variety of commercial applications.

Open time and drying time for adhesive need to be followed for success. In this case, traffic on newly installed sheet vinyl left permanent indentations in the floor due to adhesive displacement.

All of these products are usually installed with one-part urethane adhesive. This is the same type of adhesive that is used to install wood flooring. An adhesive expert once told me that the recycled content in these products presents somewhat of an unknown, so urethane adhesives are preferred because of their superb bond strength to rubber over most substrates. I have worked with a lot of this type of flooring over the last 11 years, and as more recycled rubber products have hit the market, the variety of adhesive choices has also grown. I find installers often have a preference for one particular brand of urethane or another. Urethane is “thick” by nature and installers tell me some are easier to spread than others.

Besides the “recycled” category, there is 6 to 12 mm thick rubber sport flooring that’s used in applications like basketball or volleyball courts, weight rooms and even home gyms. These products take a lot of time to install, as they usually require two-part reactive adhesive such as epoxy, and the seams need to be “bricked” after the material is set into adhesive. This process requires that bricks be placed on top of the seams after the material is laid, to assure that the rubber flooring is firmly set into adhesive while it cures. Just rolling the floor is not enough, because these products can have a slight edge curl and reactive adhesives don’t have any “grab.”

Q: What’s the difference in thinset mortars for tile installation?

A: While I am not as well versed on tile as resilient floors, I’ve been working with tile more and more over the past six years, mostly for commercial use. In high traffic commercial spaces, I’d always recommend paying a little extra for the “premium” thinset. Repairing or replacing a tile floor is a big job, so why take chances?

Another situation is that some “specialty” tile and stone products may require a specific setting product. I learned this firsthand on an epoxy terrazzo tile project. A standard thinset doesn’t have the bond strength for this type of material because the tile is very non-porous. When you work with a tile or stone material you’re unfamiliar with, ask questions of the tile supplier or contact the Tile Council of North America (TCNA) for guidance.

Finally, a couple of points I mention over and over.

First, when it comes to trowels, Size Matters! Failures due to the wrong amount of adhesive (too much or too little) continue to be a major issue. The trowel is not just an application device, it’s also a measuring device! Second, roll the floor! Most adhesives require the use of a roller after the floor is installed, to be sure the floor covering is firmly set. You can bet that if a floor goes bad and a professional inspector comes to look at it, he or she will be looking at the trowel notch pattern to see if the right trowel was used and see if the floor was rolled.

Christopher Capobianco has been in the floor covering industry since the 1970s in various roles including retail and commercial sales, technical support, consulting, journalism, education and volunteer work. He currently is part of the sales team for Spartan Surfaces in New York City. You can reach him via [email protected].

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