# Humidity affecting drywall repair?



## blsholtes (Mar 5, 2018)

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?


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## endo_alley_revisited (Aug 9, 2016)

"When I came back, all my work had evidence of moisture bubbling on the surface of my drywall patches intermittent throughout the room. " How do you know there was moisture bubbling on the surface? Did you check the moisture content of the plaster with a hygrometer or moisture meter? Was there bubbling at the surface of the mud. And you assumed it was moisture? Or do you have evidence that moisture caused the bubbling? There may be other reasons for the mud not adhering such as efflorescence. How did you reinforce the cracks in the plaster? Did you merely coat them with joint compound? That sounds like a possible disaster in the making.


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## blsholtes (Mar 5, 2018)

Great questions. Thank you for asking them. I do not have a tool for checking moisture content, so it is an assumption. I could also describe the damage as flaking. Efflorescene is a possibility as well if the salt crystals can leach through the plaster into the j-compound. The plaster wasn't cracking so much as chunking off prior to my repair attempts. I had to fill it in very thickly at places (1/2"-1"). Will taping the smaller cracks be sufficient for future shifting? I did "merely coat them with joint compound," and I am very open to any counsel I can get on what to do going forward. What possible disasters do you foresee?

Thank you for helping.

Ben


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## endo_alley_revisited (Aug 9, 2016)

blsholtes said:


> I did "merely coat them with joint compound," Ben


That is a disaster. You can't coat a bad substrate and think anything good will come of it. If the plaster is delaminating it probably needs to be chipped away with a chisel, at least in the worst spots. And replastered.


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## blsholtes (Mar 5, 2018)

endo_alley_revisited said:


> That is a disaster. You can't coat a bad substrate and think anything good will come of it. If the plaster is delaminating it probably needs to be chipped away with a chisel, at least in the worst spots. And replastered.


Sorry, I oversimplified: I did chip away all of the loose plaster, as well as drilling and injecting adhesive at spots to strengthen some of the weaker plaster surrounding the damaged areas. I also tried to wash the wall down prior to applying the joint compound, but given your observation about efflorescence, I apparently didn't wash well enough. If I had washed better, would you say it is still best to replaster rather than just using joint compound? I did a lot of research on this prior to starting, and could not find any voices saying that plaster was best or joint compound a bad idea. In fact, I found the opposite, though I understand how hard it is to filter through all the bad advice out there. That's why I tried to find multiple sources and consider all the warnings and problem cited. Most importantly have you seen from experience that, all other factors mitigated, joint compound just will not work to fix plaster damage? Thanks again for sharing your experience. I am deeply grateful!


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## Mud n’More Mixball (Mar 18, 2018)

Hang a picture over it and call it a day.


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