self-leveling underlayment

To fill out some dips in my floor prior to installing laminate, I visited the local hardware store for advice. They sold me a bag of "Mapei Ultraplan 1" self-leveling underlayment. The bag instructions laid out only the water-mix ratio for mixing the entire bag. Since I didn't need that much, I visited the web site to get clues on how to mix smaller batches.
In reading the technical documentation, I wasn't much further ahead in understanding how to mix a partial bag. But, one thing I noticed was the direction on where you can apply the product. It can be applied over a playwood sub floor like mine, but only 1.5" in thickness. Mine is standard 1/2 inch.
The product I used in another room of my house was "Lepage Poly Underlay" - it had no such subfloor thickness prescription (the store was out of this product, which is why I ended up buying something different)
I'm guessing that the 1.5 inch limitation on the Mapei product is there for a reason, and I'd be better off not testing that limit. I should go back to a product that meets the specs of where I am installing it.
Dissenting votes?
--
LorneS

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<< playwood sub floor like mine, but only 1.5" in thickness. Mine is standard 1/2 inch. >>
IMO 1/2" subfloor is substandard, unless you are living in a mobile home. Probably OK for some tract house codes, too. Do the directions refer to the product thickness of 1.5" or required subfloor of 1.5"? Have you actually talked on the phone to customer service at the company? They might be glad to help you
<< In reading the technical documentation, I wasn't much further ahead in understanding how to mix a partial bag. >>
Note the weight of the bag. Weigh out 1/4 of that (or whatever), on your bathroom scale and add that fraction of the full bag water rquirement. Easy, yes?
Joe
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If you've ever watched these bags being filled you would understand that the contents are not mixed. For this reason they encourage using the whole bag.
Happy modeming, Bill
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I suspect the 1.5" requirement is because the cement based self leveling underlayment won't hold up if the subfloor flexes, which 1/2" and even 3/4" is prone to do. I think you'll find the thin section of the underlayment will crack and turn to powder when the subfloor flexes. You might be better off laying a layer of 1/4 inch underlayment or hardi-backer instead of using the self-leveling compound.
HTH,
Paul
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