Moisture barrier? And use it under plywood below cabinets?

mudwormJune 17, 2011

We are putting down floating laminate for our flooring throughout the house. (I know laminate is not the best choice, but at this point it is for our budget.)

The laminate manufacturer "recommends" a 6mm moisture barrier under their planks. They sell it and it's plastic. I always wanted cork underlayment (thicker version for its warmth, and sound proof quality), but do not want to void our warranty. The first question is will a 6mm cork underlayment serve the same purposes as a 6mm plastic moisture barrier does?

Now, we are going to put down plywood below our cabinets to make up for the thickness of the flooring that we will lay down later. Will we need moisture barrier under the plywood as well?

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Your post is not making sense to me. 1st of all, if you are required to lay a moisture barrier, you are laying this over cement? if you have a basement or crawlspace under you, you do not need moisture barrier. Who is this manufacturer? Cork is one of the best underlayments made. Something doesent sound correct with the post at this point...Need more info to precisely help you!

    Bookmark   June 18, 2011 at 8:02AM
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Floortech, do you mean to tell me that you didn't take notes last time I asked questions on the Flooring forum (three pages ago by now)?

Just joking. I'm sorry that I did not provide the full context. The area that we are laying the laminate down includes one room with plywood subfloor and two rooms just with fir "hardwood" planks. Underneath is a crawl space.

We got the Costco Harmonics Laminate floor. It's 5/16" thick and comes with a 1/16" foam backing. On the installation instructions, it says "Harmonics flooring with underlayment already attached to the flooring panel requires the use of a moisture barrier (included int he Harmonics Installation kit) over concrete subfloors and is recommended over wooden subfloors."

Now that I just typed out the sentence, it dawned on me that it's not saying the moisture barrier is recommended for the wooden subfloors; rather, it says the panels with foam backing are recommended for wooden subfloors. But the customer service rep I talked to also told me that moisture barrier is recommended (not required) for wooden subfloors. Did we both get the grammar wrong?

Anyhow, dear Floortech, what would you do if you were to install our floor, esp. with the plywood under the cabinets. We just hope to have a solution that can provide the maximum warmth and comfort (but cork flooring is out of our budget right now).

    Bookmark   June 18, 2011 at 1:43PM
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1st off, it is really not needed with the crawl space, but f it is included...use it as it will not hurt anything at all. Cork is out as you should really not place the cork under the attached pad as it could jeopardize the joint integrity. As far as warmth, laminate is about as warm of a hard surface that you will find when placed on a wood subfloor. You will be fine...just continue along the lines that you are on! Good Luck

    Bookmark   June 19, 2011 at 1:01AM
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I just read their Accessory Information (a PDF sent by the customer service) and saw in it "Pad-Backed Planks: Needed for every installation over concrete, recommended for installations over wood." Great! There is no longer any grammatical ambiguity there. If it's recommended, I will use it.

One more question though (sorry for pressing for it): now that we are clear that we'll use the moisture barrier, do we also need to put it below the plywood under the cabinets? We'll lay the laminate up to the plywood and the seam will be hidden under the toe kick. And we'll do the proper spacing at the seam as required.

    Bookmark   June 19, 2011 at 1:38AM
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It is always advised to use Poly sheeting under any floating floor reguardless of if it has attached underlay, loose underlay, or a cork underlayment.

    Bookmark   June 20, 2011 at 11:28AM
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