Exposed gypsum core? What's the issue?


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Old 11-28-19, 12:09 PM
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Exposed gypsum core? What's the issue?

About to work on a small 2nd floor laundry room in a condo built in 1979. Noticed that near the baseboard there were patches of paint bulging/bubbling. I took a 5-in-1 to the area and paint/cardboard/etc came right off with minimal force. Did I expose the gypsum core of the sheetrock (see images)? What caused this and how do I correct? Note that if I keep peeling at the bulges the cardboard-like material just keeps coming off. Also, there's the rusty nail in the photo as well - figured it's from the high humidity of the laundry. New DIY-er here - any help is appreciated.
 
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Old 11-28-19, 12:27 PM
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Welcome! Dont know where you live or how cold it gets there but high humidity and condensation in cold temps can cause the paper to separate from the gypsum. You get a lot of cold air coming under the bottom plate in winter months and so the problem is usually confined to the area behind / around the baseboards.

Similar problem in hot humid climates but it's the humid outside air hitting the colder air conditioned air inside that can cause the condensation.

You probably need to remove the baseboard and cut off whatever is loose. You usually want to prime it with an oil primer like Kilz original and let it dry before you attempt to patch it. Durabond or lightweight setting compound is usually a good idea for your first couple coats. Paper or fiberglass tape should usually be embedded along the edge of your repair on your first coat.

Or if it's too soft to patch, you could always cut out and completely replace the drywall.
 
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Old 11-28-19, 01:03 PM
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If you don't want to use an oil base primer you can use Zinnser's Gardz instead.

While you want to remove what paper is loose you don't want to remove more than you need to. Scoring around the area with a utility knife first will help limit how far the paper pulls off.
 
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Old 11-29-19, 04:10 PM
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How thick is the cardboardy stuff? It looks like celotex or something like it. Is this wall shared with an adjacent unit? Is it an exterior wall? I wonder if this is an attempt at soundproofing. I think if it comes off easily I would be for taking it off and replacing with new drywall but what to nail to?
 
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Old 11-30-19, 12:18 AM
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It's very thin - about 1/16 of an inch. And yes, the laundry room sits both adjacent to a bedroom in my unit as well as the laundry room in the other unit. I was also wonder what the sound proofing mechanism would be given where the laundry room is located.
 
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Old 11-30-19, 10:08 AM
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I've never seen the paper on ordinary drywall look so fibery. Are you in the US?
Any chance the washer hookups or drain are above the damaged area?
If the paper or cardboardy stuff is adhered to the gypsum core then I would leave it. Without that facing, whatever it is there is no strength to the gypsum. For stuff like this I use FibaFuse scrim. It comes in long rolls 3' wide or maybe it's 1 meter wide. I mix up some 5 minute mud and embed the scrim into that then add more on top of the scrim. Wait until it sets and add another or more coats until it is built out flush. But if this is otherwise conventional drywall I think I would opt for replacing the area. the caulked or painted with buildup of the baseboard might be an irritating issue.
 
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Old 12-01-19, 04:36 PM
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Yes, I'm in the southwestern US. And yes, the hookups are directly above the area.
 
 

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