Stuff matters

I recently looked at a problem floor that turned out to be related to how the installer timed the adhesive. In this case, it was solid vinyl tile (sometimes called luxury vinyl) in a wood-look plank. It was was installed glued down over a concrete slab.
The installer did a nice job, having prepared the slab well, so it was smooth, and the fitting of the planks around doorways and other obstructions was excellent.
By Christopher Capobianco

However, within two months the owner started to experience gaps at the ends of the planks. On investigation, I learned that the tile was installed in August. I was seeing it in November. The planks were exactly the right length, so there was no shrinkage. However, there were gaps at the ends of the planks.

Christopher Capobianco

There were two issues contributing to this problem. One was acclimation. The material was onsite in advance, which was a good thing. However, the air conditioning was not on, so the temperature was on the warm side. It’s not unusual for vinyl flooring, edging and base to grow or be inadvertently stretched during installation.

Once the conditions cool to normal, in-use temperature, the material will relax back to size. That’s why you often see gapping in vinyl flooring, base and edgings. In this case, the way the installer applied the adhesive made the condition worse because the holding power of the adhesive was compromised.

The installer spread the adhesive and let it sit for several hours before installing the floor. He told me he had even left it overnight in one of the rooms. He had used the correct adhesives for the vinyl-backed plank, but had followed the procedure as if he was installing vinyl composition tile (VCT). That is, a very long open time and working time. As such, the adhesive dried out, even though it was still tacky when he laid the planks. Tacky does not mean there is enough bond strength to hold the tile in place. The adhesive instructions said, “Loss of adhesion can result if the flooring is not installed within the working time of the adhesive.” The open time was published at 60 minutes and instructions said that the flooring must be installed within two hours. In this case, they went well over that time.

So, what is meant by open time and working time?

Open time is the amount of time the adhesive needs to be open to the air after it’s applied. This time will vary depending on the adhesive itself, the porosity of the substrate and the humidity. A wet-set adhesive will have a very short open time because it needs to be wet when the material is placed. That means a finger touched to the adhesive bed will have a “smudge” of adhesive and a mark will be visible on the floor from where the finger touched.

In this example, the vinyl plank measured exactly 48 in. as it was supposed to. However, acclimation and adhesive open time were not followed and that caused the tile to gap.

In this example, the vinyl plank measured exactly 48 in. as it was supposed to. However, acclimation and adhesive open time were not followed and that caused the tile to gap.

Epoxy and polyurethane adhesives are an example of a wet-set, and there are many others. Pressure-sensitive adhesives need a longer open time, so they are allowed to dry completely. That means a finger touched to the adhesive bed will not have any adhesive and there will not be a mark on the substrate as these types of adhesive are generally coloured and turn clear when ready. Carpet tile and VCT adhesives are examples of floor coverings installed by this method. Transitional pressure-sensitive is another type of adhesive often used with vinyl-backed flooring. In this case, the adhesive will start to tack up but not turn clear. That means a finger touched to the adhesive bed will show the lines from the trowel ridges. Slightly wet but starting to develop some tack.

So, those three methods describe how the open time is determined. Working time starts when the installer starts to lay the tile and ends when the adhesive is covered with flooring. Many adhesives today have a short open time; for example vinyl back tile and sheet, rubber and linoleum have a short window. On the other hand, the nature of VCT and the adhesive used to install it allows for a much longer open time so the installer can spread more adhesive at one time.

With the large amount of vinyl plank and tile being installed today, there seems to be some confusion throughout the industry. VCT had been around for decades and a lot of people have installed it. Installers often prefer the longer working time so they can spread large areas of adhesive and take their time laying the material. For VCT that’s usually no problem. However, there is more demand on the adhesive and more holding power is needed for material with non-porous backings like solid vinyl and rubber. Those adhesives have a much stronger bond if they are still wet.

In a previous column I talked about the importance of using the right adhesive for the product being installed. Vinyl adhesives don’t work well on rubber, VCT adhesive doesn’t work as well on vinyl-back material and so on. In this case, the working time is another key that’s not the same with all products.

In the example of the installation I visited recently, it was a shame because the installers did a good job. However, their mistake was assuming all vinyl gets installed the same way and that is not the case. Vinyl composition and vinyl plank are not the same and the installer learned that the hard way.

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 christopher@SpartanSurfaces.com.

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