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Test time for RH test

Hello Ernesto,

Let me clarify please. MVER will not vary wildly if measured appropriately. Changes in atmospheric conditions will have an effect on MVER though, so it can change. Proper testing is done under controlled atmospheric conditions. The greatest change I notice in vapor emission rates is after concrete has equilibrated under a flooring material.

Concrete that dries from the top only will have a drier upper horizon after several months of drying, and MVER tests may be acceptable. When a vapor restrictive flooring is placed on the slab the moisture in the concrete redistributes over time and the top horizon becomes wetter than it was when initially tested for MVER. This is especially noticeable when there is a blotter layer under the concrete or there is no vapor retarder under the slab.

The RH in-situ test method will show the potential a slab has for causing problems. It shows us the relative humidity inside the slab. Through testing and many years of real world experience we know that when the relative humidity is below 75% we will not have a moisture related flooring problem. Oftentimes a manufacturer will even accept 80% RH if they have had success at that level.

The RH test is not swayed by a polished slab surface, sealers, atmospheric humidity, and is not as susceptible to temperature swings as a CaCl test is. It is a much more stable test, and as such is in my mind much more trustworthy. I can easily cause false readings with a MVER test, but cannot cause an RH test to be inaccurate when conducted properly. Side by side in hundreds and hundreds of tests I have conducted, RH is accurate and dependable.

Please do not be confused by RCConcrete's statement that RH varies 5% per 2 degree variation in temperature. While this is somewhat factual for a small band of temperatures, if it was a true statement overall then we would go from 100% RH at 32 degrees to 0% humidity at 82 degrees. Obviously this is false. We also want to conduct our RH tests at the service temperature of the floor we are testing. Floors that are on grade are quite thermally stable, and even raised slabs usually vary only a degree or two.

RH testing is extremely accurate and gives us a better picture of the true potential of concrete.
JD Grafton
Concrete Answers for Flooring Problems
[email protected]

Quote:Let me clarify please. MVER will not vary wildly if measured appropriately. Changes in atmospheric conditions will have an effect on MVER though, so it can change. Proper testing is done under controlled atmospheric conditions. The greatest change I notice in vapor emission rates is after concrete has equilibrated under a flooring material.

CCsolutions, yes I am quite aware about equilibratuion of the interior mositure of a slab. Yet, I find it difficult to believe that there will be no variance of temp when someone moves into a structure. Then why do the rh test methods state that we test both cacl and rh in a controlled invironment as well?

Little background... I have been in the biz for 32 years, have glued thousands of floors of various type...all types and I have performed hundreds of cacl tests and a few rapid rh tests. I have also talked extensively to Ron at wagner and also Bob Higgins. I am not an amature by any means.

That said I have never...ever witnessed a failure of my own due to moisture issues. Weird, maybe, maybe not. I have done a few inspections where has cupped some floors on laminate and wood. I view these issues as very rare, for me anyway.

I believe that just because a slab may have more or less moisture in it does not mean thats what is going to come out of the surface, being surface structures are all different, some more porous than others.

I also take issue with the cacl test method of grinding off the surface structure you may intend on adhering your flooring to as long as you know there are no bond breakers on it. This must give you a false positive reading, least more positive than not grinding because your opening all the pores of the surface structure.

IMHO in a perfect world we would have to take off the entire surface of the concrete, test it, seal it, test again with a cacl test to make certain the values are within industry standards. You cannot do that with a rh test. But then again no one could afford flooring either.

The perferred industy method out here where I live in concrete world is to just seal it and forget it. They probably have just as many issues as with people who do test, maybe not.

Question, are proponets of relative humidity testing telling us that there have Never been ANY issues of flooring failures when tested with the ASTM F2170 ? Can you absolutely state and warranty that I will not have any moisture issues if I test with the 2170 method?

Lastly, I see the industry looking for the quick accurate way to test a slab to appease the ASTM committee's that make these rules we must abide by. But it seems no one can come up with that sort of system. It is simply to complicated. Therefore no one wants to test anymore and they are willing the throw the dice.

Please keep in mind that moisture testing is just indicating the amount of moisture being emitted, the humidity in, or the water content of a concrete slab. Different tests give different readings of different issues.

Ernesto, you said you used CaCl tests frequently and you see variations in readings that make you concerned. You stated that grinding the floor changes your MVER readings by opening the pores. This can be true.

My point is that CaCl tests are commonly inaccurate and don't address issues such as burned surfaces, poor vapor barriers and rapidly changing atmospheric conditions. We can get much more consistent readings from in-situ RH probes, and when we use documented testing and past experience proving that these RH levels are acceptable for flooring, yes, there are warranties provided by manufacturers and companies like mine.

My job is to figure out WHY a floor failed, and HOW to repair it in a way that is guaranteed to NEVER have a moisture related failure. So many times I have read reports of acceptable CaCl testing initially, only to have catastrophic failure in 6 months to 5 years.

In-situ RH testing is much more reliable and can reveal problems MVER tests cannot. And I guarantee it.
JD Grafton
Concrete Answers for Flooring Problems
[email protected]

I cannot agree with your statement. You cannot guarantee a floor will not fail using any of the testing method nor can you guarantee the MVER will not change.

Everyone seems to think that this 2170 is the cure all for moisture testing. I doubt that. Even if a slab has a vapor BARRIER it can be comprimised and also water can percolate into it from the sides.

And just because a slab darkens under plastic does not mean there is a sufficient amount of vapor movement to cause a failure. Been there done that before cacl tests were the norm.

Ernesto Wrote:nor can you guarantee the MVER will not change

Actually I can assure you the MVER will change. It will change to almost zero when a floor is encapsulated with a vapor retarding flooring.

The question we always had to answer is: How much moisture in the slab will redistribute as the slab reaches equilibrium after we place a moisture retarding flooring on it?

The old method of testing was to place a CaCl test on the floor, and guess that the amount of vapor being emitted was an indicator as to how dry the slab was and how much water is trapped within. This method is far too easily fooled, and the newer in-situ probe method is much more reliable.

And yes, I can guarantee a floor will never fail due to moisture. That isn't a stretch to believe.... there are zillions of floors out there not failing. But I would never rely on a MVER test to make that guarantee.
JD Grafton
Concrete Answers for Flooring Problems
[email protected]

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