As most users say, this forum has been a great source of information! After some arguing with the significant other we've decided to put in a floating bamboo floor on a grade concrete slab. We live in the great Chicago land area.

Most of the information I've read from the web and the Wood Flooring book is for full hardwood floors. The information says to put a vapor retarder such as the Bostik MVP4 before laying flooring. However, talking to the store we're purchasing the product from that it would be overkill to do this to the concrete since we're doing a floating floor. He said that we only need to lay a vapor barrier (Eco-Ultra Quiet underlayment). Is the underlayment good enough?

I haven't done any moisture tests as of yet but doesn't appear to be much moisture content after the recent rain. The concrete slab is at approx. 20 years old.

Thanks for the help!

Most times you'll be alright if grading is ok and theres plastic under the slab. But then if you read most guidleines from those underlayment manufacturers they say to test for moisture and if it reads high, use six mil plastic beneath their underlayment.
MVP4 is great for this but it could be construed as over kill. I like over kill. Better than your floor being ruined. These type underlayments can easily be over whelmed by MVE.

Thanks, now I'm having a hard time finding a place near me that has a supply of the MVP4, are there other alternatives out there? I've seen Mapei WFM Planiseal recommended but it appears that it has been discontinued?

Well it appears I might save some money by just using 6 mil plastic and overlayment on that even though I'd like to overkill for my own house. =)

Thanks for the advise!