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TOPIC: Moisture in Concrete Slab

Moisture in Concrete Slab 20 Nov 2012 06:17 #5990

The floor in my new home was just removed due to moisture damage from the concrete slab. A Calcium Chloride test shows moisture above tolerable levels for laying the new floor. My installer in bringing in fans and dehumidifiers but has not yet removed the old glue residue from the concrete slab.

Won't the adhesive residue covering the concrete slab impede the drying process?

Does anyone have suggestions for finding the source of the moisture and/or solving the problem so the new floor can be installed satisfactorily?

Moisture in Concrete Slab 20 Nov 2012 10:24 #5992

  • tdmac
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Yes the adhesive should be removed anyway for a new adhesive to glue down a new floor. there are 3 GREAT adhesive companies that have Moisture Warranties with their moisture membrane qualities.
Taylor Adhesives, Bostic MPV and Sitka. are all products with written warranties and absolute moisture protection. Your slab could take for ever to dry out. That is not the Option!!
Is your floor an engineered floor??? Dont go solid.. no matter what!!
Get the proper adhesive, read the instructions and have him do a TEST area for a week ASAP and then determine to go forward. Follow that Manufacturers specifications of that adhesive and you should be back to normal soon. Dry out is if you had a major floor ...Did you?? In my opinion, the high moisture content in your slab , if not a flood, ( you are not in New Jersey,? )....is over 3 to 4 points on a Tramex or that with a calcium chloride test, means that you have some under ground source of moisture or water trying to evaporate through your slab. All slabs have moisture vapor in them. It must or it would be powder. Why your slab has higher moisture is due to some source, drainage around your slab, hard pan holding the rain water from percolating down into the soil etc. Water is the heaviest thing on earth,( except mercury) so water wants to percolate down thru gravity. Moisture vapor will come up through the porous slab thru osmosis and capillary action and try to evaporate An engineer or a person like my self might get the almost exact answer, but that could be a relative theory. Now if you had a flood, a broken water pipe in your slab , that is a different scenario.
my 3 centsTDMAC

Moisture in Concrete Slab 20 Nov 2012 11:02 #5993

Like Tom says, if flooded it can take a slab 3 times as long to dry out verses a new slab's water drying out. So, a calcium chloride test will not be sufficient to determine the true value of the possible MC of the slab. You would need to do an insitu (relative humidity) test. You can do a rh test with adhesive residue on top.

But, if the installer did not correctly prep the surface of the slab for the CaCl test ie; removing adhesive residue and open time, you could get a false reading. Either way the adhesive must come off to install the new floor and dry it out. Course, maybe the old adhesive was one that is waterproof when set. In this case maybe your slab didn't soak up to much water. The only way to tell in this case is an rh test. I prefer Wagner Rapid Rh. Yes, they read higher than other re-usable insitu tests but then there is a reason, thats because they strictly follow ASTM 2170-11 protocol for design.
<em>edited by grooving on 11/20/2012</em>

Moisture in Concrete Slab 21 Nov 2012 12:48 #6000

To save time & money by applying the rental cost of the equipment to the solution. As recommended above proper floor prep & testing will set you up for success. Keep in mind ASTM F1869 Calcium Chloride measures the moisture vapor emission rate (MVER) at the time of testing. It takes 3 site visits over 5 days to properly complete. ASTM F2170 measures the relative humidity (RH) 40% into the slab. This takes 2 site visits over 4 days to properly complete. The RH reading is what the slab will be throughout after the flooring is installed. Both tests properly done will give you enough facts to make an informed decision. In closing, compare warranties, they are not equal!

Moisture in Concrete Slab 22 Nov 2012 10:23 #6006

And lets not forget that after 3 days (72 hours or so) your only getting the mver of a 1/2 inch of concrete with the ASTM F-1869-11. but in a matter of an hour your Rapid Rh will give you a reading within 3 percentage points. But to be ASTM compliant you still need to go the 72 hours for rh as welll which I think is over doing it.

Moisture in Concrete Slab 27 Nov 2012 14:06 #6058

Thank you all for the excellent responses. My builder believes the moisture came from a leaking toilet in the adjacent townhome. That may be so but it would not explain why my neighbor on the other side has the same symptoms of cupping and splintering that I had and his floor is approx. 2.5 feet higher than mine on the grade.
I'm a little confused about the testing. First, the glue residue has still not been removed. The calcium chloride test was done on a small section of the floor that did not appear to have glue on it and registered close to 6 pounds after sitting for approximately 68 hours. Can you explain to me the idea of the multiple site visits associated with the calcium chloride test as mentioned above?
After the calcium chloride test was done, a disaster recovery contractor came in and set up fans and dehumidifiers. At the time, they tested the concrete with a concrete moisture meter and found readings between 4 and 6 pounds. After 5 days, they came back and found only slightly lower moisture readings. They plan to leave the fans and dehumidifiers in place for another week.

I'm concerned that the moisture problem may be one of an ongoing nature, possibly related to drainage, as mentioned above.

What steps would you recommend at this point - an evaluation by an engineer?

Thanks again for all the helpful responses.

Moisture in Concrete Slab 27 Nov 2012 14:51 #6059

Basically for a calcium chloride test first thing to do is lightly grind down the surface to remove contaminants, return next day (24hrs)and set the test, then return after 72 hours and weigh the dish, course you must pre-weigh the dish first with everything on it including the tape, then after and calculate the difference in weight gain to get the lbs/24hrs/1000sf. Must do a minimum of 3 tests.
I also do a ph test at each site, and do a water droplet test to check if contaminats are gone, this is why a greater area then the dish surface is needed. Follow the instruction that come with the test!

If you have new concrete and no contaminates, if surface is CSP-2 to 3, then you can set on top of the carbonated surface if you plan to adhere to that. This is not an approved method for testing though. They like you to lightly grind anyway. Surface ph after grinding should not be less than 9. It's all debateable though. This is why ASTM F-2170-11 is taking over althigh many manufacturers still allow a CaCl test.

A meter will only read maybe a half an inch into the surface and you can get false high readings with it over any adhesive residue.

Moisture in Concrete Slab 02 Dec 2012 08:25 #6142

My installer came back on Friday and attempted to remove the adhesive residue with bladed scrapers. While they removed some, there is still a significant amount of residual adhesive covering the floor. They are trying to figure out how to remove the rest. They told me that certain equipment cold not be used since it is a finished home and it could cause damage to walls, cabinets, etc.

Any suggestions on how to remove the adhesive residue?

Also, since someone mentioned drainage as a posiible issue, I will mention that puddles form on my front lawn when it rains.

Thanks again for all the great input.


Moisture in Concrete Slab 02 Dec 2012 09:50 #6143

I've skim coated with Ardex feather finish and glued many a time. Sotblast it off or skimcoat. Those are the options. Shotblasting is a great way to get a pristine new surface. Plus there is no danger of contamination of surfaces or air quality, especially if there is asbestos in the cutbac, and thats a rea possibility.

Sorry boys and girls, if a consumer needs help and his people are not up to par on specs I am going to help. Thats what forums are for. You get help when you need it too.

Moisture in Concrete Slab 02 Dec 2012 17:29 #6145

  • tdmac
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Grooving, This client sure does have a real problem that needs some engineer to look at. It sounds like an Insurance claim to me. That water drainage problem must be reviewed and corrected with proper 'French" type drains as they are called. Once that drainage is corrected, will the soil under the slab start to let the water percolate?? An engineer needs to decide that problem since a lot of the neighbors water caused the problem.
The soil around that slab should be checked and grading may be needed. Now that slab will still retain a lot of vapor even with the dry-out attempts.
I sure agree with your Shot blasting safely doing the job right and get that slab clean.
You only have ONE SHOT at this problem. Then a good quality Moisture Membrane adhesive process can be used to install a good Engineered Wood floor.
I will try to keep my comments on this forum not as technical as we did with List Serve, where many young pro's discussed professional techniques. LINKEd In seem a good place for that. Cheers

Moisture in Concrete Slab 03 Dec 2012 06:44 #6146

Thank you again for the feedback.

Are there any obvious downsides to shot blasting?

My floor was removed on November 15 and the residual adhesive is still there while the drying equipment continues to run.

I'm surprised that my installer has been unable to figure out how to remove the adhesive residue.

As I mentioned previously, they attempted to lay the new floor on November 16, on top of the adhesive residue and without testing the concrete for moisture. If I haven't already mentioned, the original floor was laid on a new concrete slab without testing it for moisture.

Again, I appreciate all the great advice.

Moisture in Concrete Slab 03 Dec 2012 07:35 #6147

Shotblasting is commonly used to dry out slabs in commercial applications when the slab is taking to long to naturally dry and or someone powertroweled the surface to closed up so it can't dry at all. No downside to shot blasting.

Moisture in Concrete Slab 03 Dec 2012 09:27 #6149

Tom suggestions does make sense, indentify and correct problem before you proceed with slab dry down
Roy Reichow

Moisture in Concrete Slab 13 Dec 2012 16:26 #6211

I've been is this situation a few times with customers. Once the moisture is at at an acceptable level, the existing glue needs to be removed with a concrete grinder.(preferably an industrial size on that look like a buffer) Once 90% of the glue is removed you may now apply a coat of Sika mb epoxy primer (Sika® Primer MB 2-component, solvent free, low viscosity, epoxy primer for use under wood flooring products that require protection from concrete moisture.)Some cases a second coat is required. Finally you may install a new floor with the piece of mind that the concrete has been properly sealed and warrentied by Sika.

Moisture in Concrete Slab 13 Dec 2012 16:39 #6212

Update: My builder has removed the adhesive residue using cat litter and a hand scraper. He tried Goof Off with little success. The fans and dehumidifiers have been running 24/7 since November 21 and the moisture readings have dropped somewhat. The moisture readings using a Tramex Concrete Encounter range from about 3.0 to 4.5 lbs/1000 sq. ft/24 hrs. The last calcium chloride test showed 4.2 lbs.

Thanks again for all the great advice and information.

Moisture in Concrete Slab 13 Dec 2012 17:06 #6215

First off, I would not want to remove cutback adhesive with anything but a shot blaster because it could have asbestos in it.

Second, a Tramex Concrete Encounter does not read in lbs/1000 sq. ft/24 hrs, it reads in percentages. http://www.tramexltd.com/Our_Products_Details.aspx?ID=19

Moisture in Concrete Slab 13 Dec 2012 21:37 #6222

Grooving - Thanks for the correction. If the manufacturer (Shaw) requires a calcium chloride test of 3 lbs or less before installing the floor, can you tell me how this might be compared to the moisture percentage readings provided by a Tramex Moisture Encounter? Thanks!

Moisture in Concrete Slab 14 Dec 2012 08:21 #6224

Pete, there is no correlation between a CaCl test and a CME. Same with a CaCl and an insitu test. Although I think there might be a method but I don't have the means to prove it.

Moisture in Concrete Slab 26 Dec 2012 09:12 #6274

I hope everyone had a Merry Christmas. Another question: When Shaw sent a representative to inspect my wood floor, he placed a moisture meter on the wood floor and reported moisture content of 20-25%
When I later asked what he used, he said it was a Tramex Concrete Encounter. I'm confused because I understand that the Tramex CE reads up to 6% moisture and I didn't think it would read concrete through a wood floor. The device did, however, look very similar to the Tramex CE.
Can someone tell me the appropriate meter to read hardwood floor moisture content by simply laying the device on the floor? The device he used did not involve prongs that penetrated the wood like some other wood moisture meters.

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