Hi Everyone, I'm relatively new in drywall work, mostly doing small repairs, but one job I took on is proving frustrating. I'm trying to repair an interior tower at a church. It was plaster, which was damaged due to leaks in a roof. The roof was repaired, so I proceeded to apply joint compound to fill in the gaps. I was succeeding until a heavy rain revealed a small leak, so I took a two-month break to wait for the roofers to fix the leak and for the walls to completely dry. When I came back, all my work had evidence of moisture bubbling on the surface of my drywall patches intermittent throughout the room. The room is closed off from all HVAC systems, so it is subject to sub-freezing temperatures. There is an access panel in the ceiling through which I can see light from the tower above. Given that the tower above is not sealed off from outside weather, the room is thereby exposed to exterior humidity. I'm wondering if the humidity of the room is just too high and if that could lead to the drywall bubbling? After all, the damage does seem to be only on the surface of the wall, which suggests the moisture is not coming from a roof leak behind the plaster and lath boards. It could be continuing issues with roof leaks, but the patterns of damage do not support that theory. Does my hypothesis about high humidity fit with anyone's experience? What recommendations does anyone have about how to fix it? Could painting it help prevent future damage? If so, will latex paint work?