Can you adhere drywall to plaster?

whiskeykid

I'm renovating a 1905 farmhouse and have to pull the exterior wall out of the main floor bathroom in order to fur out the 2x4 walls and properly insulate. The bathroom was renovated sometime in the past, and the walls are plaster over metal mesh. I'd actually like to leave the plaster because it's in good shape and forms an interesting arched ceiling - probably pretty 'classy' in its day. I don't however, want to re-install plaster on the exterior wall. The bathroom is long and skinny - 4' x 11', and the exterior wall is one of the short 4' walls. Is there a way to transition between drywall and plaster? I've heard that drywall mud won't stick to plaster. Any ideas?

buletbob

Are you sure On the 4' width. was there a tub presently installed in the room. I am having a hard time figuring where they placed the tub. unless it was on the outside wall. which would of been a four foot tub which they still make . and side wall would leave you with an 18" walkway.
what i do is take and old hatchet and chop the corners of the plaster where you want to remove. make sure you cut the mesh all the way through. if not when you go to remove the old plaster you will be pulling the wire fro the wall you don't want to disturb. you could fir the wall out or What i do is use double drywall 3/8" then 5/8" over which here in my region usually matches up with window and door frames about 3/4 to 7/8". when we Spackle onto plaster we wet the plaster down with a sponge so it slows down on pulling the moisture out from the Spackle. we never had any problems with this technique. I can't see why you were told that unless this person had some work done improperly. BOB.

clasact

the plaster has a tendency to pull the moister out of the mud quickly which will cause shrinkage and cracking but if you do like BOB said it will slow it down also do the transition in several coats but yes it will stick to plaster just fine

whiskeykid

Yeah, it's a 4' square tub! It's basically a big shower with a corner seat. I can't imagine anyone other than a child bathing in it. It reminds me of a tub in an RV.

Actually, the wire mesh was added later and the exterior wall still has the original lathe and plaster. And wood shavings insulation!! When you wet the plaster with a sponge do you get the plaster soaking wet, or just damp?? I guess it's hard to quantify...

Thanks for the advice

buletbob

The whole idea As mentioned by Clasact and I was to slow down the drying time so the plaster does not pull the moisture from the Spackle as quick as if it was dry.

bjbatlanta

Absolutely, mud will stick to plaster. Cutting the plaster out straight and patching back in with drywall if the toughest part. Chopping will work, but tends to break out past where you want it to. Sawzall will work, go slowly. Drywall cutout tool with a tile bit will work. Just get it as straight as possible. I would recommend using a "setting" type compound on at least the first coat to minimize shrinkage and it's much harder (once dry) that ready mix. HD and Lowes both sell a USG product that come in varying setting times. It is a powder form which you add water to. I've never had to dampen the plaster, but I'm sure it won't hurt and may help....... Certainly worth a try. Best of luck.

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AtlanticWBConst.

We have done many old-wall plaster repairs over the years.

Word for word, what was stated here is right on the money =

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whiskeykid

Right on. Thanks for the advice folks!

drewhart

i've used the setting type (durabond in a brown bag) for the tapping coat, then followed by the light weight all purpose joint compound ready mixed for the second coat (third if you need it, as this type is way easier to sand than the setting type) many many times on plaster walls and they have never even shown a crack since. i have never wet the walls first either. also tape over any cracks that are in the existing plaster also. they will probably not come back for quite awhile this way. paper tape is best also.

bjbatlanta

If you can get the "brown bag" Durabond, it is the hardest of the setting compounds. You may have to go to a drywall supply company. HD and Lowes stock the easy sand setting compounds, which will work.
True the lightweight ready mix sands easier, it also nicks and scratches easier. I would not recommend using it. Regular ready mix dries harder. Drew is correct advising taping any existing cracks.

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