I am renovating a 50 year old house's basement to increase living space. I am located in Southern Ontario, Canada.Along the outside walls, I read that a water barrier of 4-6 mil poly should be first put up with about a foot of extra at the bottom to wrap up the front of the stud walls. Then installing studs, then fiberglass insulation then another layer of poly and then the finished surface of drywall or panelling. The concrete block walls have been painted with some sort of paint prior to my purchase of this house.
People that I have talked to say that the first layer of poly which is against the cold block walls is not needed and will cause more harm then good. Is there any truth to this or is it just a myth? Can I leave that first layer of poly there or should I remove it and only install the last layer which would be sandwiched between the studs and the drywall?
Also, I wish to lay down a layer of the same poly on the concrete floor prior to just laying down an underpad and final carpet. I am not going to build a subfloor. Is this acceptable in most cases?