Installing Shaw Glueless Laminate on a Concrete Slab - Underlayment Question

I have about 160 sq. ft. of the Shaw glueless laminate to install on a bare concrete slab. I also got the 2-in-1 underlayment that they sell to prevent moisture and heat loss (I think that is its function).
Question is I had someone make a strong suggestion to me that before installing the laminate, to install 1/4" (5.2 millimeter) exterior grade plywood over the concrete. This is supposed to soak up some of the variation in the floor (not much if any as far as I can tell) and help prevent moisture from affecting the laminate? Said to use liquid nails or some such adhesive to hold it down to the concrete.
But reading the manufacturer's instructions it says to not use the 2-in-1 underlayment over organic surfaces (i.e., wood subfloor?), and if there is any "wood flooring" on concrete to remove it before installing the laminate. Not sure if that statement was meant to include "wood subflooring" (which is not really "wood flooring", like oak is).
I am going to call Shaw for clarification but just wanted to know if anyone had any practical experience they could share.
Thanks!
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Manufacturer knows best.
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If you are concerned about moisture, plywood shouldn't be your first choice.
I used wonderboard (waterproof tile backer board) to even the floor. The previous post is on the right track because the manufactuer can give the best advice for their product.
c_kubie
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c snipped-for-privacy@yahoo.com wrote:

You should have paid attention to the manufacturer of the wonder board, durock, hardi-backer, whichever you used. Because none of them are designed or made to be installed over a slab.
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wrote:

To whom are your talking?
You seem to be operating as the self appointed NetCop this week, what with your obsession with moving top posts to where *you* think they should be positioned and complaining about posters not quoting in their replies...
And here you are guilty of what you criticize in others, amazing...
DJ
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DJ wrote:

go back to sleep...
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I'd go by what the manufacturer says. Any type of wood sandwiched between the concrete and the plastic barrier seems like a potential problem long term. It would absorb moisture and eventual rot, mildew, show know what.
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Don't think heat loss but rather sound.

Bad idea, read the other posts above.
This is supposed to soak up some of

Don't know about Shaw but you could use 2-in-1 (done this many times) but not required for wood subfloor because of the extra expense. If you have a moister problem in your crawl space below the wood subfloor you should address this first else even the 2-in-1 won't be effective.
and

I guess the 2-in-1 will trap moister in the wood flooring above the concrete slab. I'm doing about 1,000 sf of laminate with 2-in-1 over bare concrete - no problem, my concrete is dry. There is a DIY concrete moister test - a square clear plastic sheet over concrete and duct tape all around, don't remember how to judge moister content but you could ask your manufacture about it or found it in Google.
Not sure if that statement was meant to

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Have you looked at the relevant website:
http://www.shawfloors.com/ShoppingExperience/Installation/LaminateInstallation.asp
KB
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I installed about 1000' sq in my house over concrete slab (Florida) about 1 year ago using Shaw Pacesetter 2 and the 2 in one underlayment (never had a moisture problem). My floors seemed level before I started but when I finished I did notice a couple of spots that floated. In spite of that it came out great the only exception being my Greyhound having to learn how to walk again (slick floor). I would definitely buy again and don't be surprised if the floor makes the room look too good. I ended up repainting every room. Deals can be had on the Internet as the local folks couldn't even come close on the price and did not even want to deal on quantity. And make sure you buy the install kit which includes shims and tools. Greyhound

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