Adhesive Breakdown and Flooring Betrayal
The new floor is in, and the guests are arriving for the big event. What’s that smell? Why is glue seeping from the cracks between the floor tiles? Welcome to adhesive breakdown, a costly result of excess moisture and high pH under the floor covering.
Moisture vapor naturally evaporates from the surface of concrete floors. Suppose the installers ran a calcium chloride test to measure the slab’s moisture vapor emission rate (MVER) and got a result of 2.76 pounds of water per 1,000 square feet per 24 hours. Flooring manufacturers commonly set MVER limits of about 3 to 5 pounds, so in this scenario, the contractor likely went ahead because the reading was under 3.
What Went Wrong?
If the floor failed and only surface testing was done, the slab’s internal relative humidity (RH) may have been much higher than the surface test suggested. Once the slab is covered, moisture from deeper in the concrete keeps moving toward the surface. That moisture can dissolve alkaline salts in the concrete, creating a high-pH solution at the surface, right where the adhesive is.
If the moisture and pH are high enough, they can break down the adhesive. The floor covering no longer bonds to the subfloor, and the adhesive can soften and seep out instead of holding.
MVER Tests
The calcium chloride test, which measures MVER, has been used for decades. A dish with a known weight of anhydrous calcium chloride is sealed under a dome on the concrete surface for about 72 hours. The dish is then weighed again, and the MVER is calculated from how much moisture the calcium chloride absorbed. Flooring manufacturers have commonly required MVER results under 3 or 5 pounds before installation.
Experience has revealed limits to this method. The calcium chloride test doesn’t measure the concrete’s pH, which is tested separately (ASTM F710 includes a surface pH test), and it doesn’t show the RH deeper in the slab. So on its own, it can’t tell contractors whether conditions are right for adhesive breakdown.
Relative Humidity Tests
That’s where in-situ RH testing comes in. RH testing measures the moisture condition inside the slab, so contractors can confirm that the concrete is within the limits set by the adhesive or flooring manufacturer before they install the floor covering. Wagner Meters’ Rapid RH® makes in-situ RH testing cost-effective and easy.
Handheld concrete moisture meters from Wagner Meters can also help contractors quickly find wetter areas of a slab that need further testing before they cause adhesive breakdown.
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Jason has 20+ years’ experience in sales and sales management in a spectrum of industries and has successfully launched a variety of products to the market, including the original Rapid RH® concrete moisture tests. He currently works with Wagner Meters as our Rapid RH® product sales manager.
Last updated on October 14th, 2026
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The issue you have talked about here it’s all are important to know for all. Thanks for this content.
This is happening in one of my basement rooms (We didn’t install the flooring, but the prior owners did not too long before selling the house). Will a dehumidifier in this room help with this issue? (for reference, the same flooring was installed throughout the rest of the basement and there is no issue like this with the rest of the basement floor).
Thank you for your help!
If the subfloor is not level throughput within manufacturing specs , what possible problems could arise in the future??
Freddie:
Thanks for the question. The question isn’t level as much as flat. Without flat, flooring may not adhere properly to the subfloor, there can be hollow spots, and/or flooring can break or crack, just to name a few things. This is obviously dependent on the type of flooring product being installed.
Thanks,
Jason
Can something in concrete react w/flooring adhesive and cause heat?
About a year ago after plumbing backup that could not be cleared, wood flooring and concrete removed to reveal deteriorated cast iron piping. New plastic pipe, concrete and flooring installed. Now dark areas appearing on wood flooring and they are very warm. Warm enough that I would guess that under the wood it will be HOT. No evidence of moisture but I think the spots generally follow where the repairs were done.
Would appreciate your expertise and thoughts.
thanks, John
John:
I can’t say I have ever heard of flooring adhesive causing heat under the floor. I would contact NWFA, National Wood Flooring Association, and see if they can recommend someone to come take a look at the floor and diagnose the problem. Good luck.
Jason