Adhesive Show Through in Vinyl Flooring

With The change of vinyl flooring going from felt backed products to vinyl backed products, the majority of adhesives for resilient flooring are now pressure-sensitive adhesives. The problem of
show-through has become greater than ever before.

With felt back products, you installed the flooring into the adhesive while it was still in a wet state regardless of what type of subfloor you were installing over. Today, with the change to vinyl backed flooring products, there are many subfloors were you must allow the adhesive to dry to the touch. Most adhesive show through issues are with commercial flooring products. Generally, commercial flooring products have little or no embossing or texture to disguise the adhesive show through, let alone subfloor issues.
Below are some causes that can lead to adhesive show through.

Adhesive overlap. Adhesive overlap is a major concern. It is a problem that is magnified by high gloss finishes. It’s amazing how many times I see a flooring issue of this type in a hospital. I hear the same concerns expressed by the staff over and over again. They often have no idea how much a high-gloss finish will high light even the slightest irregularity in the material, adhesive or substrate. Their only concern seems to be how shiny the surface of the floor is. And at almost any hospital, you will find a huge amount of low-level lighting, which just magnifies the whole issue.

Adhesive gapping. The opposite problem of adhesive overlap, is a gapping of the adhesive. This is when the adhesive is purposely left a short distance away from the already troweled adhesive resulting in a void between the two adhesives spreads. When applying the adhesive, trowel the adhesive close enough to eliminate the overlap and eliminate the valley.

Incorrect trowel notching. This is the biggest issue I face. The correct notch trowel for the proper application of adhesives has always been a concern within the industry. When trowels wear down, they do not apply enough adhesive. Then they are either re-notched and leave an irregular spread or the incorrect notch is used, which leaves either too much or too little adhesive. This also will lead to not getting the correct spread rate of the adhesive. Next time you visit your grocery store, look down the aisle and you will probably see every adhesive trowel mark in the floor; incorrect trowel notching.

Paint roller application. Several adhesive and flooring manufacturers have recommended trowel-applied adhesive to be back rolled with a short nap paint roller to flatten out the trowel ridges.
The adhesive will dry-to-touch quicker, and because there is a larger bonding surface than trowel

ridges a better bond is achieved. I also see more installers using this method for VCT tile installations. To be successful, the installer must keep the roller clean and prevent it from leaving balls of dried adhesive on the finished spread. An easy way to do this is by keeping the roller wrapped in a piece of plastic to keep the adhesive wet and fresh.

Spray application. The most recent method is the spraying of adhesives for resilient materials. This is not a new method for applying adhesive, as it has been used with carpet for decades. However, when used for resilient there are two main concerns: The blowing of debris creating bumps beneath the material’s surface, and any unevenness of the spray showing through the material. If those two concerns can be eliminated then the spraying of an adhesive may have a major place in the resilient flooring industry.

Adhesives that are designed to dry-to-touch can be sprayed smoothly and evenly, and then the likelihood of show through can be almost eliminated. Attention will have to be paid to keeping the spray smooth and even, with special attention paid to overlaps of the spray.

Another advantage is if the spray adhesive can be applied thin enough and indentations that occur in the adhesive can be kept to a minimum.

Applying adhesive correctly is still the biggest challenge we have in the resilient flooring industry. Some flooring manufacturers supply trowel blades with their adhesives to ensure that

the correct trowel notching is used with their flooring product. Rolling and spraying of adhesives

are growing in popularity and are helping to overcome some of the industry concerns. No matter what method you use, remember to do it right and follow the manufacturer’s recommendations. Don’t take shortcuts that do not work or cost you more money or aggravation.