Know What’s Below: The Challenge with Wood Look “Waterproof” Flooring

Figure 1: Waterproof flooring with closed cell foam backing; HDF core.

By Bob Goldstein

I have had a spate of calls recently about wood floor issues with brand-new floors not living up to what they are advertised to provide. Digging deeper with both homeowners and contractors, it turns out that these problems aren’t actually with real wood floors, but are occurring with “wood like” floors, either laminate or LVT, which tout being 100 percent waterproof.

Wood-like or wood-look products install much like real engineered wood floors, so the extra work offered to the professional wood floor installer is a positive thing if they educate themselves on the differences between the flooring and make sure they read all instructions. That last part is easier said than done. I visited several big box stores where the waterproof floors were being promoted. Not one could offer me a printout of the installation instructions or had any real-world knowledge of how to install them. I was able to get what I needed by calling the manufacturer’s tech support or chatting with an online person.

Here is one of the most egregious examples of throwing both the homeowner and the installer under the bus: 1,800 square feet of flooring installed in a home on a golf course in south Florida. The home is concrete slab on grade. The floor is a click profile floating product. Because both parties were assured that this flooring was 100 percent waterproof, no moisture testing was done on the concrete and no vapor barrier was used. (Keep in mind, the backing on this product is a layer of cork.)

Within two months, there was standing water in the kitchen, the flooring was delaminating, buckling, and the whole house smelled of mold. The original flooring in the home was carpet. I spoke with a tech support person about the issues with the floor and he told me to read the installation instructions and that moisture testing is required and a vapor barrier should be used if the moisture is higher than what they recommend. I was able to track down a PDF file of the installation instructions and found some very interesting information. They do say to check for moisture using the CM method (ASTM D4263) better known as the plastic sheet test. It further states that a reading of 2.5 percent is acceptable. This confuses me as this type of test doesn’t give a quantitative number; it’s either wet or dry, so what tool was, or is, used to get the 2.5 percent?

We should all be familiar with ASTM F1869 Calcium Chloride testing and ASTM F2170 in-situ probe tests. Both provide go/no go numbers; CC 3 pounds or less, in-situ probe, 75 percent RH or less for wood and related floors. So, if you get a number above the manufacturer’s recommendation, there is usually a remedy such as using 6 or 8 mil plastic sheeting under the floating system. Nowhere in the instructions is moisture mitigation mentioned.

The bottom line is that 100 percent waterproof floors are a myth. I looked at several brands with varied construction, all claiming to be waterproof, one made with MDF core (medium density fiberboard) with a sheet of closed cell foam glued to the back. How is this supposed to stop moisture from under the floor getting to the fiberboard? As mentioned earlier, some have a cork backing, which also is not waterproof. Others have a HDF (high density fiberboard) core that is coated, but they still recommend cleaning up spills right away.

I bring these issues up because a lot of wood floor folks took it on the chin with overly ambitious claims from some bamboo manufacturers over the years. We learned the hard way that solid bamboo must be treated like solid wood and acclimated to its in-use environment out of the packaging. Strand-woven bamboo also needs to be acclimated like real solid wood, keeping in mind that acclimation for these products takes longer than real wood due to the resins and glues that hold them together, and the fact that they are finished on all six sides. Because the installation instructions for so many of these floors (even now) can be ambiguous, the finger is always pointed to the person who did the work.

My advice is simple: CYA – cover your assets! Read all instructions and then opt to be very conservative, use your acquired knowledge and experience and reach out to the NWFA for suggestions and options when any part of the installation process feels wrong or instructions are vague.

One last point. An old saying that we have always used during NWFA training: “Sometimes that job you chose not to do turns out to be the best job you never did.”

Bob Goldstein is in Technical Services, Training & Sales at Vermont Natural Coatings based in Hardwick, Vermont. He can be reached at

4 thoughts

  1. Good advice Mr. Goldstein, but I wonder why check with NWFA about non-wood products. The last contact I had with the NWFA before we divorced about 6 years ago was that they had no specs on Bamboo products and had no interest in them since they are grass and not wood. I suspect they also have no technical data on LVP products.

  2. The CM test is not the same as the mat test. There is no quantitive number given by the mat test, but there is with the CM test, (ASTM 4944), commonly known as the Calcium Carbide test. We don’t use this test in the US. It’s only used across the pond.

  3. While I’ve been a wood flooring pro for 36 yrs, I also work part time at a big box store in the flooring dept. While there I’m a big advocate of following the instructions as given on the box. Whenever installing over concrete we highly recommend a 6 mill vapor barrier.., I tell them about the plastic test for moisture. Most homeowners don’t realize that concrete releases moisture. As far as vinyl plank I tell them the glue strip is waters resistant as far as the adhesive being able to resist water. The click and lock is waterproof to the extant that water doesn’t hurt it and since there is no thing holding it down( as both are floating floors) water doesn’t affect it in that way, but water can still get underneath it and can cause problems. I ” push” the click and lock, because you can unlock and take it up to help in the drying process underneath it. I believe pergo has a spillprotect line and if you follow there direction to a t, they consider it waterproof, put I don’t see how.
    And yes I do push wood.

  4. I enjoyed your article on this subject of water proofed flooring, after over 40 years in the flooring Industry, the last 30 years as a floor covering wholesale rep for a leading southern calif flooring distributor, I just retired December 2018, I’m sorry to say its old news that needs repeating.
    To some Retailers and flooring contractors, know what your selling, can’t tell you how much time I spent going over specs and guidelines on Mfg products from the Mfg to educate these people and I’m told by these customers: If I tell the consumer everything there is to know about the pros and cons of flooring, they probably wouldn’t buy from us, because of the extra charges to supply a moisture protection or explain about RH, humification, acclimation in a controlled environment, etc. Remember, the consumer still has to make that decision on paying extra for their flooring investment.
    Some retailers and flooring contractors do get the jobs because of their truthfulness, be honest up front and have peace of mind, when a problem arises, you’ll have the answers for the Mfg. that you followed their guidelines, and then you contend with the warranty. When you have the proper tools to check the jobsites conditions such as moisture , while some other subcontractors that do work for retailers don’t invest in the tools of the trade, moisture meters, Hygrometers, RH probes, problems occur. If you don’t use the tools of the trade, expect repercussion from the manufacture.
    Thanks for your article
    Dan Hernandez

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