I am about to install some engineered flooring on the 2nd floor (1st above ground level) of a condo. The subfloor is concrete slab and we plan on floating the floor. I've been told that the proper way to go about it is to install...

1) Some 6mil vapor barrier like this stuff.
2) The noise abatement underlayment on top of that; we're going to use floor muffler.
3) Lastly, the engineered floor on top of that.

However, I wonder if this is ok? I feel like the floor won't be solid if we put both the moisture barrier down as well as the floor muffler, although I've been told that this is pretty standard. So two questions...

1) Moisture doesn't seem to be an issue, so do I need the moisture barrier or not?
2) If I need the barrier, is there another underlayment which would make the floor more stable?

Thanks for reading.

-BB

FloorMuffler IMO is over rated. They claim superior moisture protection, that it ; "Exceeds industry standards by over 700% (3lbs/1000sqft/24hrs) by the calcium chloride testing ASTM F-1869-11. I don't understand how they come up with this 700% figure when a calcium chloride test @ 3lbs/1000sqft/24hrs is a standard high reading for many floors.

However, this is test and numbers are actually pretty low numbers. Then on the next page they tell you to use 6 mil if tests shows high mver. Moisture levels can change so it's just good common sense if you have no vapor barrier under the slab.

You absolutely should use 6 mil plastic. Many underlayment manufacturers suggest it if there is high moisture emissions. And you cannot tell just by looking at it although some near experts can.