I have been in a few newer homes (10 years or less) and have observed mold and subsequent black staining in the top 2 feet of a poured basement corner.
I am trying to figure out why.
Inconsistancies between the houses are:
Parially finished and unfinished basements.
Direction of corners
sump pump no sump pump.
no discernable outside leaks
The only logical explanation I can come up with is high humidity at some point and the cold foundation wall lowering the dewpoint.
Am I on track or is there another possible reason?
I live in the midwest.