How can I determine if moisture in a basement is due to condenstation vs intrusion through walls?
I have used a piece of plastic like a garbage bag tape one to the walls and 1 to the floor and peel it off the next day if it or they are wet it is coming through the slab and or walls (quite common). The slab might be an easy fix , I have used 2 part epoxy paint for concrete with really good luck to seal floors, cut the amount of water in the dehumidifier drastically. I have only used epoxy paint on block and poured walls not natural stone so I am not sure how well epoxy paint would work there maybe some water seal? Like Thompson’s I have used that on pavers to reduce freeze cracking and that worked so it may help the walls also. Most of the moisture I have found in a dry basement is from the floor and bottom foot or so. It is amazing how much moisture can make it into a dry basement. Check with the plastic taped all 4 edges to see where the problem is coming from. This should prove it to your self and since dry a nice dehumidifier may be all that is needed but in my experience painting sealed things up well.