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High Rapid RH readings??

#31
Well ddemento, you are doing work that is out of my area of expertise. That doesn't mean I can't advise using my background and common sense gained from dealing with these issues for a long time though.

Warning: There are some people involved with projects that cut corners or just don't understand what long term flooring success requires. These people will not be around when the floor fails, or will claim some type of voodoo occurred and that is why you now have a ruined floor.

When I looked at the floor manufacturer's website I saw they require 75% RH for commercial glue-down installations. I saw no reference to your application directly. I would advise that you call the manufacturer and explain the details of what you have. Explain your concerns. Get their advice and get it in writing.

Stick with accepted concrete testing methods as dictated by the flooring manufacturer. Nucleo readings will not be recognized.

Be sure any testing using CaCl is done according to the latest ASTM which will involve grinding pretty deep into the concrete surface. This will increase the MVER reading.

Trust your RH readings! The floor is wet internally. You need to decide if all that moisture will ever have an effect on the flooring. If you put a vapor retarder between the concrete and the wood it will help, and it may be an acceptable way to proceed. Ask the manufacturer for their recommendation. They had something on their website about gluing down inexpensive sheet vinyl first, but I'm sure there are many ways to accomplish a good vapor retarder. If you are laying a wood sleeper system over the concrete I would think a sheet vapor retarder will be fast, inexpensive and completely serviceable.
JD Grafton
Concrete Answers for Flooring Problems
[email protected]
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#32
(11-16-2011, 11:04 AM)CC Solutions Wrote:  If you are laying a wood sleeper system over the concrete I would think a sheet vapor retarder will be fast, inexpensive and completely serviceable.

If it is in a school in the USA using a MFMA wood system you would have to apply a MMS like Koster. The Home Depot Poly is not enough anymore as they've been shown to not perform well enough.
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#33
(11-16-2011, 11:32 AM)eaadams Wrote:  
(11-16-2011, 11:04 AM)CC Solutions Wrote:  If you are laying a wood sleeper system over the concrete I would think a sheet vapor retarder will be fast, inexpensive and completely serviceable.

If it is in a school in the USA using a MFMA wood system you would have to apply a MMS like Koster. The Home Depot Poly is not enough anymore as they've been shown to not perform well enough.

While Home Depot 4 or 6 mil poly may not be enough, I'm sure we could find an acceptable vapor retarder. In fact some mitigation systems use a multi-layered vapor suppression tact.

And I believe the job is in the Great White North. Big Grin
JD Grafton
Concrete Answers for Flooring Problems
[email protected]
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#34
(11-16-2011, 10:50 AM)eaadams Wrote:  
(11-16-2011, 10:05 AM)ddemento Wrote:  So here is my dilemma, do i let them go ahead and do the floor or do i be an "a-hole" and tell them to its not ready? Maybe they should do it. After all they are responsible should something happen and the flooring contractor has to guarantee the floor. Right? But should the floor fail, it will be huge head-aches for me since I am the GC.

This is the problem I have with GC's. If the floor is reading high it is reading high. You have a duty to your customer to build a building that will not have problems. Don't do it. Don't risk it. If you get sued how much will the legal bills cost you? More than doing it right the first time.

For Q1 you need to contact the manufacturer. Go around your sub if he isn't competent enough to understand RH. Every reputable manufacturer knows RH. Every reputable manufacturer has a local rep who should know rh.

For Q2 this is a bad question. Asking if anyone has installed a wood floor over high RH is like asking has anyone painted a wall. There are thousands of different paints for walls.

If your RH is high, don't do it. Go get your own expert.

To reply to eaadams, i know my duties and it is my client who insists on installing the floor even after I warned them of the risks. And it is my client who has hired an independant lab to challenge my results. All i was trying to say was that if the sub-trade is willing to install and still offer a guarantee, then why not let him. Any GC out there has and will do this. Obviously if the floor fails there are repercussion for everyone.

Anyways, my trade has said he will not install any floor over 4% readings with his meter, since he has had problems in the past with anything higher. The wood manufacturer accepts 2% but will tolerate 4% (or as per website 75%RH). I think that's what we will be shooting for.

I was also contemplating putting down a poly as a vapor barrier, but my trade said it will not work as humidity will get out.

Curiously, i took a reading today of my probes and the good news is they existing ones went down about 5% from last week (down to 94%). However, the new probe installed last week still measures 99%. Can it be the old probes which we were questioning went down and new one stayed up there. (and for those wondering, no I do not wet drill)

Thanks.
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#35
You are correct when you say once there is a failure "there are repercussions for everyone". I commend you for your persistence!

Poly can be overlapped and appropriately taped I suspect, again this is not what I do.

A reading of '4' must be from an electrical impedance meter. These readings can vary in meaning due to concrete density and make up, they are also affected by reinforcement oftentimes.

At least your probes are alive!! Tongue Movement is good! 5% is a LOT of movement in a week, a very positive sign!

If the client is pushing to install there's not much you can do besides give your best advice and caution and get something signed to the effect that you do not wish to proceed because it will be in violation of the manufacturer's specifications.

Good luck and keep us posted!
JD Grafton
Concrete Answers for Flooring Problems
[email protected]
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#36
Fascinating discussion.

My two bobs', based on your questions, Ddemento, about the flooring install on which the clients are insisting:

"Floating" wood floors are only slightly less susceptible to moisture related failures, as the pulp base of the plank is generally very porous and can take up more moisture than a solid wood before showing signs of cupping etc. Plus, being that the floor is not sealed in-situ, the joins have miniscule gaps which allow some vapour to escape.

Mind you, some floating floor manufacturers claim that these miniscule gaps make their flooring the panacea for moisture problems, which is rubbish. I’m making a few assumptions here when you say “floating”. Either way, the RH readings you are getting are not ideal for anything. Just beware that some floating floor manufacturers are a little optimistic about their performance over a wet slab.

In the case of glue-down adhesives for wood floors, polyurethane-based ones like Bostik Ultraset (not sure what it’s called in the US) accept higher RH, while semi-rigid low-foaming ones can sometimes require no higher than 70%. Take JD’s advice- get the suppliers/ manufacturers to give you some assurances either in writing or some pdf spec sheets.

Quote:Anyways, my trade has said he will not install any floor over 4% readings with his meter, since he has had problems in the past with anything higher. The wood manufacturer accepts 2% but will tolerate 4% (or as per website 75%RH).

Are these moisture content figures, as opposed to RH, and if so, do they give the choice of using either? As JD said moisture content has been found to be mostly irrelevant, especially for wood floors in my experience. RH is king.

Oh, and I should add that, as eaadams mentioned, a moisture barrier of some sort will be necessary. But again, some vapour barriers are only designed to slow the vapour emission down to a rate which the flooring can tolerate. With high RH readings such as yours, some systems simply won't work, see our other discussion here Smile :-

http://www.wagnermeters.com/concreteforum/Thread-MMS-Are-some-unreliable-with-high-RH

The problem with socialism is that you soon run out of other people's money.
- Margaret Thatcher

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#37
A proper vapor membrane can help you help. Stego is one word or some other visquine might stop the blight. Think about double asphalitc tape and make sure to to double lap seams 12" minimum. Some manufacturers have better tape.
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#38
First, whats up with that outside wall on demento's pic's? LOL WTF?

Second, Bostik's newest 2&1 adhesives are rated 85% rh max.

If you want wood and you have any iffy readings from F-2170 testing, the keyword is "isolate" ...from the concrete.

I do wood over concrete all the time....yawn. RolleyesRolleyes
Stephen Perrera dba
Top Floor Installation Co.
http://www.tucsonazflooring.com
http://www.floorsavior.com
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#39
(11-16-2011, 05:03 PM)Ernesto Wrote:  First, whats up with that outside wall on demento's pic's? LOL WTF?

Block wall? Water pipes around the perimeter supplying the radiant heaters? What are you looking at? Huh
JD Grafton
Concrete Answers for Flooring Problems
[email protected]
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#40
Where are these pics? I have a special place reserved in hell for water radiant heating.
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