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Used too much joint compound, but not cracking yet


miamicanes's Avatar
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09-23-08, 10:19 AM   #1  
Used too much joint compound, but not cracking yet

I'm in a bind at the moment. After ripping out all the drywall from one wall, and the lower drywall from 2 other walls due to mold, I replaced it with GP paper-free mold-resistant drywall (DenShield? DensArmor?). I taped it using setting-type/90-minute compound and self-adhesive yellow fiberglass tape, then did a second coat with USG lightweight compound w/dust control. So far, so good (mostly).

The problem is, on Sunday I got frustrated by its appearance, as well as the ugly original drywall that I'd removed the wallpaper and adhesive from, and proceeded to apply the remaining half of the USG compound AND TWO MORE tubs of it to the entire wall surface... new AND old drywall. In some places, I probably put 3/8" of compound or more. I really slathered it on and went over the deep end, creating de-facto plastered walls. I went to bed with a dehumidifier running in the room, and woke up Monday morning to a room that looked BEAUTIFUL.

Well, sort of. The original drywall that I coated with joint compound had rippling and wrinkles just like the warnings against using too much compound say will happen. But the paper-free drywall? Stunning. No cracks, no bulges, no ripples, and not even a hint of discoloration or anything bad. This morning, everything looked the same -- new and old drywall just like they were yesterday.

Therein lies my dilemma. I obviously need to sand off the excess compound from the old drywall and resurface it properly with primer and setting-type compound to repair the damage, but what about the paper-free drywall? It doesn't just look "OK", it looks SPECTACULAR. Did I basically just waste some money by using unnecessary and excessive amounts of compound to skim-coat the paper-free drywall? Or is THAT almost guaranteed to fail, eventually, just like the old-type drywall did almost immediately?

 
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09-23-08, 12:40 PM   #2  
Welcome to the forums!

I've not worked with the paperless drywall but it is constructed different than the conventional drywall. I suspect on the old drywall you had, had places where the paper face was missing. These areas should always be coated with a solvent based primer first. That will prevent the moisture in the j/c or latex paint from partically disolving the gypsum which causes the wrinkling.

Generally the biggest prolem with appling ready mix j/c too thick is it will crack as it shrinks and dries. If it doesn't crack it should be fine. I always try to apply a skim coat as thin as possible both to avoid any problems and to save on material . . It is also easier to control and have a level skim coat job.


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09-24-08, 11:00 PM   #3  
Well, the compound smeared on the DensArmor still looks fine as of Day 3. It might be my imagination, but the "ripples" I saw in the OLD drywall on Monday seem to be gone, too!

I DID discover one thing, though... Valspar white color-changing ceiling paint (the stuff that goes on purple, and dries to white) seems to dry to pale blue on unprimed drywall compound. Every single spot where I patched a hole I cut in the ceiling to pull cat5 cables by covering it with self-adhesive fiberglass tape and USG lightweight low-dust compound is instantly-visible and pale blue.

 
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09-26-08, 06:49 AM   #4  
I was recently told not to mix setting compoud with drying compound because when you sand, one will sand faster than the other. I guess you have no choice but to try it.

 
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09-26-08, 03:30 PM   #5  
I know manufactures never like for their product to be intermixed with another but there have been a few times where I accidently over thinned ready mix joint compound - I'd add enough durabond in the mud pan to make the j/c usable. I've never noticed any problems.


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09-26-08, 05:41 PM   #6  
It wasn't the manufacturer who told me that. It was a couple guys who do sheetrock on a daily basis.

 
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09-26-08, 06:00 PM   #7  
I've done alot of rocking over the years- some professionally, some for friends. If you have 3 days drying with no cracking, your doing great. I assume then you bought the blue pail, not the gree, as it shrinks less, which is what results in the cracking. So sand smooth and get ready for paint. Yes, i don't think you need to coat the new drywall, unless you have texture issues your trying to work out. Just be sure you do a good job priming the rock before you paint it- otherwise, you will have different colors as the paint will dry faster where the mud is thicker- its like a sponge until you seal it with primer.

 
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