Waterproof floors

Don’t oversell and don’t under-test

Christopher Capobianco

I was planning a writing evening after work and thinking about my column that would address some issues related to concrete moisture concerns in floor coverings. Coincidentally, I started my day on a conference call with several people from my company. As we were reviewing a variety of flooring products in our line, one of my more experienced colleagues had a few choice words about the category of so-called waterproof flooring that really struck a chord with me.

With the growing popularity of a resilient floating floors such as loose lay, click LVT, WPC and so on, there is more and more marketing that has the word waterproof right up front. You’d sometimes think this is a new category called waterproof flooring that didn’t exist before. This gives the impression that somehow vinyl floors were not waterproof before, which of course is not true. Claims are being made that these floors can be installed in wet areas because the material will never swell, and so on. But what if?

These claims can give the impression that somehow if the floor gets flooded, there is no problem. That’s certainly not true, because if a flood were to occur, the entire floor would have to be removed so that the substrate and the flooring material could be allowed to dry out; not to mention the walls if you had a bad flood. Again, technically the material is waterproof but it’s more complex than that. My colleague and I are not the only ones concerned about these products being over-sold. I prefer, when I describe these products, to talk more about the other advantages such as acoustic benefits, simpler installation, smoother transitions to adjacent floor coverings such as carpet tile, and oh, yes – it’s also waterproof so if you have a flood, theoretically you can take it all up, dry it out and put it back down again.

This 5 mm click vinyl plank was installed as a floating floor but did not stay flat due to concrete moisture issues in a new slab. In other areas of the same project, planks on an older (dry) slab looked perfect.

That covers a little about the whole of “waterproof” when it comes to moisture from above. What about from below? The issue of concrete moisture issues never goes away, and more frequently today, the conversation turns to some kind of floating floor as a solution. I work with a lot of rubber flooring for fitness applications and am often asked about the interlocking “puzzle” tile as an option for damp concrete. Along the same lines, products like vinyl and WPC are being sold as somehow immune from concrete moisture issues. The assumption is that that damp concrete under floating floors is okay because there is no adhesive. That’s the issue, right? Well, in a lot of cases it is, but making that assumption can also get you in trouble.

So, no glue, no moisture testing, right? Wrong. Read the manufacturer’s documents and you’ll find requirements for moisture testing. Chances are that the limits are generally higher than glue-down resilient, but there still are limits. I had a good example of this on a commercial project over new concrete when a 5 mm thick click-vinyl plank installation was curling badly. When the planks were lifted, the concrete was visibly damp, and the moisture readings were on the high side. It was assumed before the floor was installed that this was not an issue, so no testing was done. However, the manufacturer did in fact have a published moisture limit. Despite the material being “waterproof,” it can be affected by such issues related to moisture as elevated pH and alkalinity that often come as moisture emits from concrete slabs.

My biggest concern about this whole issue is trapped moisture between the substrate and the floor covering.

Whether your subfloor is wood or concrete, whether it’s water from the top or moisture from below, moisture under the floor covering creates such potential problems as mould and bacterial growth. Even if the flooring itself is not affected, these are big issues, and you can bet the floor covering dealer and installer will get called back to deal with them. For these reasons, I tend to be cautious about claiming a floor is waterproof or moisture-resistant. You can certainly install a vapour retarder sheet or underlayment under a lot of floors that will protect the floor covering, if that’s recommended by the manufacturer. I still worry about moisture under the sheet, but at least the flooring itself is protected.

This floating click vinyl floor shows curling ends due to moisture vapour emissions from a the concrete slab.

So, all that said, what’s the installer to do? For starters, read the installation guides and the warranties for these products. You can bet there is language about moisture testing and there may be warranty exclusions for elevated moisture or pH levels. Don’t forget, if moisture is moving out of concrete, it often leads to elevated pH levels on the concrete surface as the alkalinity from the inside of the slab moves with the moisture vapour. That’s a warranty loophole in a lot of floor coverings and adhesives. The floor covering (or adhesive in the case of glue down floors) may resist moisture up to a high level, but if the pH reading is over a certain level, all bets are off.

So, back to a topic I’ve covered before; how to test for moisture in concrete?

The only two tests that work are the calcium chloride test (ASTM F1869), and the relative humidity (RH) test (ASTM F2170). Both methods have always required a three- or four-day process for test results. However, recent changes to ASTM F2170 have shortened that time to one day, which makes the whole process a lot easier. RH testing involves drilling holes in the concrete to take an internal reading, which is why it’s thought to be more accurate in predicting future movement of moisture from inside the concrete to the top. However, I still hear from floor coverers who would rather do the F1869 calcium chloride test to avoid drilling and RH meters, perhaps because they don’t have the right equipment and a test kit. However, F1869 is done incorrectly more often than not because one or more of three key steps are ignored. One is ignoring the three-day waiting period for results, two is the need to “lightly grind an area 50 by 50 cm” before placing the test and three is the necessity of testing when temperature and humidity conditions are the same as when the space will be occupied. Missing these details makes the test invalid, so be sure to test completely “by the book,” meaning the 2016 version of the test method, ASTM F1869-16a. I’ve done several articles here in Coverings on the subject — let us know if you need a copy.

I know this seems like a lot of trouble and many of you are saying that you’ve done plenty of floating floor installations over concrete with no issues. I have been hearing the same thing for years about glue-down floors like sheet vinyl, vinyl plank and VCT. “I’ve never had a problem!” However, all it takes is one failure and the costs can be pretty high, especially if you have not followed the manufacturer’s instructions.

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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