The concrete moisture and finish floor covering relationship (part 1)
San Francisco skyline looking from Twin Peaks
Had a recent exchange of thoughts and ideas with a long-time client and a technical services representative. Anyway, this initial informational exchange was too good not to share and to use as an introduction to a series I’ve been wanting to write for a long time. Names have been redacted because they are just not necessary to the discussion. And so, this is how it started . . .
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From my client: Below is a line from a quote I received today. The comment came from [Tech Rep at Resilient Manufacturer] when I mentioned that the spec is calling for High moisture resistant adhesive up to 99%RH. Interesting reading given what we face out here on every project.
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Note from our Field Service Representative regard Adhesive RH:
“We have no adhesive that covers 99%RH.
Any reading over 90 with [name of RH probe manufacturer] doesn’t give an accurate reading.
Another note, most tests set at sites are not done correctly.
Let’s look at day of install, ambient Temps, slab temps, dew point this is what matters.
Once our adhesives cure no moisture can impact them or re-emulsify them. Addressing day of install site conditions, controlling environment, that’s what gives an installer success.
Again, my opinion, most RH tests are a precursor to a moisture system that costs thousands and most of the time is not necessary.
DAY OF INSTALL tests matter, not RH which is an indicator, but dew point, slab temps, ambient temps, actual moisture releasing through surface that day type readings really matter.
FYI giving me an RH test result without knowing the rest of the story.
Anyone can call me”.
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And finally, I offer my thoughts
Couldn’t help but chime in.
There are adhesives that state they are good up to 99% RH ([name of a particular adhesive manufacturer] off the top of my head has a couple) but it’s important to keep in mind what that statement is saying. It is saying that the adhesive will continue to function “as an adhesive” up to the stated limits and not that it’s going to protect the adherend from moisture related damage. As an example, a hardwood adhesive, good up to 99%, will keep the hardwood stuck to the subfloor but the hardwood will still cup and discolor.
Not a big fan of [name of RH probe manufacturer] RH probes due to the way they are intended to be used – they tend to read high because [name of RH probe manufacturer] insists that the probe itself sit in the hole for 24 hours or more- this is contrary to the governing standard. The longer any RH moisture probe sits in the hole, the greater the tendency for “creep”, i.e., a relatively slow and small gradual change, variation or deviation from a planned value in a measure; characteristic of electronic equipment during prolonged usage or exposure to harsh conditions.
RH tests (and calcium chloride) do have a spot in the overall scheme of things but [name of technical service representative] is correct, day of install ambient temperature, ambient relative humidity, slab surface temperature, dew point, Tramex impedance meter readings and surface pH all have at least an equal importance in determining if an installation will succeed or not.
The in-situ RH test will assist in determining the chances of liquid water developing through condensation in the airspace along the bond line. That water, alone, will not cause any properly cured adhesive to “re-emulsify”. However, if the water from condensation solubilizes salts that are present on the concrete surface, then the caustic nature of that solution (condensation water and alkali salts) will indeed make any adhesive fail.
Roland