Originally Posted By: jpeck
This post was automatically imported from our archived forum.
You are in PA, it’s a basement, it’s getting chilly there by now, the “old poured concrete” may be sweating moisture on the inner surface which is running down to the bottom of the wall and being soaked up by the drywall.
I'm curious to know this: what the dry bulb, wet bulb, relative humidity, and dew point is in that wall.
Here's one guess:
Dry bulb 70 degrees (the "comfortable" 70 degrees you said the room was)
Wet bulb 68.5 degrees (just a number I pulled out of the air for this example)
R Humidity at 90% (another number I pulled out of the air for this example)
Dew Point 67.5 degrees (what the above comes out to be)
That means that wall cavity is only about 2.5 degrees above raining inside the wall, all other things being the same. Like a foggy morning.
If those numbers are anywhere near close, no wonder there is mold growing on the drywall.
Exposing it outside at Home Depot (or anywhere) is not going to cause that. If it was stored outside and got THAT wet, you would have more than just some mold along the bottom. I've built several short radius walls, using multiple layers of 1/4" drywall (to keep it from cracking) and have had to literally soak the 1/4" drywall from the surface to make the curve around the wall. I know I put more water into that drywall than a good rain would have, and when it dried out, it was as good as new.