Adhesive under resilient: A fine line

We recently had a comment from Joe, a reader in Calgary, that found my column (“Initial maintenance — what flooring contractors need to know, May 2015”) offensive because I was “telling people in the industry what the hell they should already know.” He asked for “wisdom” and said, “Tell us something we don’t know.” Well, I’ve never been to Calgary but I’ve heard it’s a beautiful place that one magazine called the best city in Canada to live in. Tripadvisor.com says, “Calgarians are really the city’s best feature” and “Calgary is modern, clean, and its people are quite friendly.” So, I made the assumption that Joe is a friendly Calgarian that just wants to learn more, and I challenged myself to come up with something to help him.

Christopher Capobianco

Christopher Capobianco

I recently inspected two complaints on sheet resilient flooring, done by different installers, and both had the same problem. I thought that these installers “should already know” how to avoid this issue, but it’s one of those really fine points that are not published in the manufacturer’s installation guide. I learned this one from a manufacturer’s technical specialist when he did a presentation in an installer training class I used to teach back in the 1980s. It’s one of those “tricks of the trade” that maybe should be in the book. And this made me think of Joe.

The problem is one I’ve seen before with sheet goods: an irregular ridge about 2 – 3 cm wide telegraphing from the substrate on a smooth sheet floor. In these two cases it was recycled rubber flooring, but I’ve also seen it in sheet vinyl and linoleum. In one case, it ran the full length of the sheet at about halfway and was visible on more than one sheet. In the other case, it ran width-wise, going across two sheets, and then jumped down a little on the next two sheets. At first it would be easy to diagnose this as an irregularity in the substrate, but at closer examination, what are the chances you’d have a ridge in the concrete slab at the same point in several different rolls, running down the middle? As I walked the job I saw a few other examples of the same problem, and I knew it must be an adhesive ridge.

The standard procedure for gluing down roll goods like carpet, vinyl or rubber is to lay the material out, trim the edges, and fold back about half way to spread the adhesive. After the adhesive is spread on the first half and the recommended open time is allowed, lay the material in, roll it, and then fold back the second half.

That’s where the problem occurred in these cases. The runs were large enough that by the time the installer got to spread the adhesive in the second half, the adhesive on the other half had hardened a little. The new adhesive was overlapped slightly. That is, it was spread on top of the adhesive from the other half. The result is that part of the material now has twice as much adhesive as the rest of the floor. If it were a carpet job, you’d never notice this, but on smooth resilient, it is visible; especially in the kind of brightly lit spaces for which large commercial projects are known. No amount of rolling, heating, wishing or hoping will make it go away. The only solution is to tear it out and do it again, and hope that the supplier has the same dye lot in stock so you don’t have to tear out the whole job.

The blue tape in this photo marks a ridge in this rubber floor caused by adhesive overlap.

The blue tape in this photo marks a ridge in this rubber floor caused by adhesive overlap.

Preventing this problem is fairly simple, but takes a little extra time and craftsmanship. When you fold back the sheet to spread adhesive on the first half, first snap or draw a line first at the point where you want to stop the adhesive. Trowel up to that line but not over it, and set the material into the adhesive. Roll the floor in both directions with a 45 kg (100 pound) roller, but don’t roll all the way to that line — leave about 15 cm untouched. Then, fold back the second half until you see the line. Don’t fold back any further than the line so the first-half adhesive stays covered. That adhesive is wet and hasn’t been rolled yet. Again, trowel that second half right up to the line but not over it. When you set the second half in, get on there and roll in both directions. The roller will crush the adhesive into the spot where the line is and there will be no adhesive overlap that causes that ridge.

One of the problem projects I mentioned also had a second problem — adhesive oozing between the seams in several places. In this case it was rubber installed with urethane adhesive and there is almost no way to remove that from the face of the material once it cures. Wood floor installers have the same problem. If you work with urethane or epoxy adhesives, don’t get any on the face of the material and if you do, get it off while it is still wet.

For sheet resilient and carpet, adhesive oozing is not just a potential messy condition; it can also affect the seam sealer. Adhesive contamination can cause a weaker bond at the seam or discoloration later on.

The cause of the problem in the sheet rubber I looked at could be one of two things, or both. Too much adhesive can be a cause of adhesive ooze-ups with tile, sheet goods or wood floors that have to be installed into wet adhesive. More is not better, and one of several possible problems with excess adhesive is it comes up “between the cracks.” In this case with a rubber floor, the spec called for a very fine-notch trowel. Urethane adhesive sets really hard, so it doesn’t take much. I didn’t get to pull up the floor to see if there was too much adhesive in this case, but I suspect it could be.

Another cause of oozing with sheet-goods installation is the direction the adhesive is troweled, which can cause or prevent this oozing condition. At the seam line, always spread the adhesive at a 90-degree angle to the seam to eliminate adhesive oozing up at the seam. If the ridges are not going in the same direction as the seam, it is less likely they will land right under the seam line. Again, a line snapped or drawn on the substrate can be helpful in this procedure so you spread at a right angle to the line where the seam falls.

I’ve been writing for various publications since the 1980s, and often thought I could write a book with so many “tricks of the trade” like these, but I haven’t done so. As I start my seventh year writing for Coverings, I’m glad to be able to share some of these tips, and I continue to welcome your questions and comments, even if you find my work “offensive.”

So, how did we do, Joe?

Christopher Capobianco is a flooring expert currently working with Forest Hill, Md.-based Spartan Surfaces, a distributor of commercial hard-surface flooring. Chris’s family lineage in floorcovering goes back for generations. His career includes time as a retailer, architectural sales rep, technical support manager, consultant, instructor, columnist and active volunteer in several organizations.

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