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plaster/drywall patch ok for hole in masonry wall?

plaster/drywall patch ok for hole in masonry wall?


Old 06-15-04, 04:02 PM
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plaster/drywall patch ok for hole in masonry wall?

apologies if my questn has been addressed previously -- i don't think i'm searching on the right terms. novice!

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 04:17 PM. Reason: new info about problem
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Old 06-21-04, 04:29 PM
Join Date: Jul 2003
Location: California
Posts: 1,722
Is the existing plaster really two or three inches thick? What kind of metal mesh is it over? How thick is the metal? How large are the holes?
How are the studs spaced?

If you have studs 16" OC or there abouts What I would do is fur them out so you have about an inch of recess then install a sheet or gypsum blue board. Not green board and not standard unless you absolutely cant get blue board. Blue board is made for plastering over. If you can't get that then install standard gypsum board and paint it with a bonding agent like PlasterWeld by Larsons Products or something similar. Then use gypsum plaster mixed two parts by volume of sand to one part plaster and spread it flush with the existing then before it sets cut it back so it is recessed 1/16" to 1/8". After it has set or the next day or whenever you can then mix up some Diamond finish plaster by USG or KalKote by Gold bond or something similar and spread it flush keeping the existing work clean. Trowel it with water before and through its set and it will be smooth as glass. If there is a texture then match the texture instead of making it smooth.
This is what a plasterer would do. The drywallers in the group will tell you to drywall it and be done with it.
Best of Luck
Old 06-21-04, 06:21 PM
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thank you!

.. for the detailed plastering advice -- i will definitely use this info. yes, the plaster really is more than 2 inches thick, and there are no studs visible in the space that opened up, just the metal mesh. that website whose URL i put in my posting described exactly what i have -- a thick sandy layer with horsehair mixed in, on a metal mesh, with a thinner layer of whiter plaster over that, then a very thin top coat (skimcoat). when i didn't get any responses on this forum after a couple of days, i went to a hardware store and talked with a guy who knew exactly what kind of wall i was talking about, and gave me Rockite to put in where the bottom layer of plaster was gone, and he advised me to put patching plaster on as the second layer, and then do a real skim coat.
much of the skim coat peeled right off the rest of the wall and i anticipate a lot of work with getting the surface right, so i am glad to have the details you passed on!

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