I just pulled up some Pergo in a basement room I’m remodelling.  Underneath are 50 year old linoleum tiles set on an uninsulated slab with no vapor barrier under the slab.  Some tiles are missing and have been back filled with Fix-All.  The Pergo installation required a 6 mil plastic sheet to be placed on the old tiles to prevent moisture from entering the bottom of the flooring.

There appears to have been condensation trapped between the plastic and the slab that has mildewed.  I plan on cleaning up the mildew with a bleach solution and drying the slab prior to doing anything else.

I would like to carpet the room.  I’ve heard conflicting advice on whether I should seal over the old tiles or not.  Some say I should let the slab breath through the carpet.  Those who say I should seal it have different suggestions on what to seal it with–some say something like Kilz, others a standard concrete sealant.

Anyone have any learned advice or experience on sealing (or not) under carpeting over an uninsulated, linoleum tiled slab?