Many flooring products today are sold as waterproof. If this is so, why do the installation requirements still have maximum moisture levels listed in the installation guides? Many even require a vapor barrier between the product and the concrete sub-floor.
The products themselves are waterproof but precautions need to be taken for other reasons. Many of these products are one form or another of Luxury Vinyl Planks and Tiles. Some of the products have a stabilizer on the back of the planks and the tiles that can have a chemical reaction to high alkali levels on the concrete, causing the planks to cup. The alkali is the cause of concern, not the moisture. Many of these products suggest a vapor barrier between the product and the concrete sub-floor to prevent this from becoming an issue.
Well, that explains the vapor barrier but what about moisture levels listed on the installation instructions?
Waterproof products let very little, if any, moisture transfer from below the product to the open air above. The only locations this can happen is a minimal amount though the lock and around the expansion gaps at the perimeter of the rooms. If vapor emissions (the amount of water vapor coming up through the concrete slab) are too high, moisture can build up between the flooring and the surface of the concrete. The biggest concern when this happens is the development of mold. This is why moisture levels are listed in the installation guides for products listed or sold as waterproof.
I hope this helps clarify why even waterproof products need to have moisture level and vapor barrier requirements in place to have a successful installation. Send me any questions you may have in the comments below.
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