I am trying to help solve a moisture problem in my in-laws basement. They have a concrete patio and a small room (not cold cellar) underneath it in the basement. My FIL (father-in-law) is replacing the drywall ceiling and had originally installed (in order attached to the underside of concrete)
(1) black roofing paper, (2) 2" rigid insulation in between 2x4s (screwed flat), (3) tuck taped seams, (4) vapor barrier, (5) strapping perp. to the 2x4s.
Moisture started to collect on the VB between it and the insulation. Researching this I'm now aware the VP and insulation together created a problem (essentially double VB). Removing the plastic seems to solve a fair amount of the problem, however ther are still some spots where moisture is collecting in some of the seams covered by tape. It's a fair amount because when removing the tape it drops to the floor in a small stream.
A few questions:
Any thoughts on why moisture is still collecting?
Could the roofing paper also be causing a problem? The tuck tape on the seams?
Can I use spray foam to fill any gaps?
Any other thoughts or comments are appreciated.