Help with vapor barrier – On-grade engineered wood
Hello All. Thanks for a great site. I have been reading quite a few Q&A regarding this topic but seems to be still confused. So I appreciate any assistance.
The home is located in the Dallas area (zone 3a I guess) and was built in 2010 with a plastic vapor barrier under the slab. There’s also gutters and grading all around.
I’m trying to install engineered wood [flooring] on the first floor (on grade) and based on the consensus here is to put another vapor barrier on top of the slab as a safety measure in the long run. This is where I get confused.
I want to use a floating double 3/8 or double 1/2 CDX stacked perpendicular or 45 angle but I don’t know what I should put in between the plywood and slab. Some suggests 6-10 mil poly plastic, some suggest DMX Airflow or Delta FL. But regardless, here’s my question:
1. Won’t the plastic you put on top of the slab trap moisture if there are any?
2. What happens to that moisture?
3. I can’t see any difference between what I’m trying to do and what others do with putting laminate under a plastic underlayment, is there?
Thanks for any input.
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