My basement was poured over rigid foam.. I believe it was 3/4" -1' thick. I want to install laminate flooring in one of the basement rooms. Do I still need to install the flooring over a moisture barrier?
It all depends on the moisture content down there. An easy check is to take a square of plastic wrap....Saran Wrap will work.....about a foot square. Duct tape it completely around the edges and leave it for 1-2 days. See if there is any moisture or "dew" formed inside it. If so, you might be able to use a roll on rubber-type membrane to protect the laminate. If you see LOTS of moisture, there might be hydrostatic pressure under the slab. If that's the case, you have bigger issues and laminate may not be the way to go...
It will still need the cushion even if a moisture barrier is superfluous. Might as well buy the standard cushion that also acts as a moisture barrier and not worry about if the subfloor foam was punctured during the pour.
I would use an underlayment that serves as both accustical pad and vapor barrier. Floor Muffler with STC at 74 and IIC at 73 is a good one we like a lot for both purposes.