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plaster v. joint compound & another problem

plaster v. joint compound & another problem

Old 06-15-04, 06:49 PM
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plaster v. joint compound & another problem

ok, having just read several previous posts, i am totally confused about plaster v. joint compound. is this just a difference in philosophy? it sounds like plaster is more difficult to get right than joint compound. but what do i lose if i use joint compound instead of plaster? quality? durability? can i use joint compound over a plaster patch?

also, i posted the following thread over on "walls & ceilings" but now i think it might be better suited for this forum. any help much appreciated.

i live in a large apartment bldg built @1920 or a little earlier. i ripped some wooden shelves out of the bathroom wall (they extend over the old-fashioned clawfoot tub, cramping movement when you use the added-on shower w/shower curtains). while the rest of the wall seemed to have a thin coat (1/8 to 1/4 inch, and variable) of white plaster, the area behind the shelving did not. the wall itself is 2 to 3 inches thick of a light brownish gray material -- it has a hard, smooth surface but in the areas where it has deteriorated, i can see that 1) hair has been mixed in and 2) there is a metal mesh of some kind upon which the wall material was applied.

it looks like a small but steady amount of water leaked into the wall via leaks in the seal between the shelf and the wall, and traveled into the wall via the nails. there is a crack in the wall where it looks like the water seeped in over time, and the thin surface plaster came off easily along that crack. i think i'll have no problem replastering the areas where the skim layer of plaster came off. but in another area, the wall itself has deteriorated. when i scraped away the loose stuff with a putty knife, i went all the way through to what appears to be a cavity inside the wall, and there is a slight breeze coming through!

from reading about plaster and masonry in various places online, including http://www2.cr.nps.gov/tps/briefs/brief21.htm
i believe what i am dealing with is old 3-layer plaster construction on a metal mesh. my question: can i just cut a piece of drywall to wedge in the hole w/liquid nails and then plaster over it? or do i have a serious problem?

Last edited by dupont110; 06-16-04 at 04:13 PM. Reason: new info about problem
Old 06-21-04, 04:52 PM
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I would think what you suggest to do would be fine. I don't do much drywall, or hardly any plaster, but if your a newbie to the patching/plastering techniques, I would do as you said. Cut a piece of drywall, zip it to the studs with drywall screws, and I guess some Liquid Nails won't hurt either. Then use fiberglass mesh tape on the edges, and float it out with joint compound. Just make sure to double prime it when finished with an oil primer, or a coat or two of GARDZ, (made by Zinsser), to add to the water proofing of the patch.

Hope that helps.
Old 06-21-04, 06:10 PM
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thanks! there aren't any studs to screw anything to -- the hole isn't that big (and i wouldn't have wanted to demolish any of the good solid wall just to find a stud), but when i didn't get any posts here within a couple of days, i went to a great local hardware store and got advice to put in Rockite up against the metal mesh, and then put patching plaster over that. i did that and it's coming along, and soon i'll be ready to put on a final skim coat. and i will keep my fingers crossed!

Last edited by dupont110; 06-21-04 at 06:12 PM. Reason: clarification
Old 06-30-04, 07:55 AM
Jean Luc
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Sounds like you are on your way. I do a lot of plaster repair and found the quickest and easiest method is to use Setting-Type Joint Compound. It comes dry in bags and is rated at cure time. You can get 15 all the way up to 90 minute cure time products from most paint/DIY stores. It is different from the regular tub-type Joint Compound in that it CURES to harden instead of EVAPORATING to harden as the regular Joint Compound does. It also won't shrink like the regular does and then crack. The thicker the applictation the better. I use it a lot and really like how it speeds up the process for plaster repair.

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