Hello all-
Im on a large remodel, 1960’s ranch, Denver, thick plaster (portland) throughout. The homeowner had new electrical, sat, cat5, phone and speaker wire run, so the electrician knock a bunch of holes to pull wire. The basement is all new, so I got my drywall contractor to bid it with drywall. But when the crew arrived to walk it with me, thet said they had never dealt with tieing into plaster before.
I PAINSTAKINGLY squared off and backed outn (to accept 1/2″ rock) every hole the electricians put into the walls, thinking that my drywallers would fill all holes with 1/2″ rock, mud it over and be done. Instead, they saw the plaster, told me drywall mud and plaster are incompatible, and left, saying they would have an answer the next day.
What is the answer? Can old plaster be patched with new drywall, and mudded with drywall mud? I know this is a fairly common occurence, and Im dissapointed my drywall crew did not research this prior.
Also, best way to adhere new knockdown texture to existing plaster walls with 2 coats semi-gloss paint on them?
Thanks group-
Torey Lenoch
Replies
Baloney -- it is no big deal to tie DW to plaster. I've cut innumerable holes, big and small, into the plaster of our 1905 house while running cable and repaired them all with DW. Also, I've removed sections of crumbling plaster from wall and ceiling and replaced it with DW, attaching it sometime over the lath, other times to the framing. I defy anyone to spot the plaster/DW transitions. I'm an (experienced) DIYer, but professionals should be able to do even better.
I've never had any problem with patches holding good using all purpose mud. If you get technical you would want to do a couple of extra steps. 1 remove any loose crud and brush clean.2 seal with a bonding agent, I used to prime it first but it just doesn't seem to matter. The Idea is stabilize the plaster. I look for color difference later and still haven't seen any sign of a reaction. So I would just clean the patches and mud it up. The less mud to fill the less shrinkage. You still need 2/3 coats. Use SR and lay it on first on big patches. The only reason I use pre mix is it's easier for me. But if you want to mix you get almost no shrinkage and it's done faster.
Clay
Agreed. Pure bunk. I've patched and patched in old plaster homes, I've done additions where the new DW butted the old plaster, no problemo. The only things I've noticed are that standard mud for me tends to pock a lot going over plaster. Why? Who knows. Someone here probably. But I cured it by sealing the wall with DW conditioner first. My second safety position is I always first coat it with durabond. More binder, stronger bond. Not to mention it fills voids like a champ.
"The child is grown / The dream is gone / And I have become / Comfortably numb " lyrics by Roger Waters
Tom Silva used DW on plaster on the last episode of Ask This Old House, What more needs to be said. LOL.
I do it all the time like the others that are posting here. If it didn't work I'm sure we would all be getting a major amount of call backs. Or maybe we are getting call backs & were all just trying to set you up for failure!!!
If it does work, "Bill Clinton greatest man alive!!"
If it doesn't work, "Dam that George Bush!!"
Be Well
PJE
Small holes in plaster can be filled with any backer (metal lath mesh, drywall or whatever) to hold the finish coat on. Use setting type joint compound (I have used EZ Sand) to go over the backer, which obviously must be secured well. Tape the joints with FG mesh tape and finish with mud.
The drywallers aren't TOTALLY wrong, though. If you had a large area on a wall, like a seam where wainscotting used to be, with plaster above, and you want to remove the wainscotting and put drywall there, chances are it will crack at the seam with the change of seasons. I'm sure it CAN be done, but whenever I mate drywall to plaster, I do not guarantee that it won't crack.
Plastering small holes is not a big deal, if you live in an area where you can get structolite (base coat), gaging plaster, and finish lime.Pete Duffy, Handyman
tlenoch,
When you say, "thick plaster (portland)" do you mean that the walls are Portland cement plaster, such as is commonly used on outside stucco jobs? If that is the case, then the drywall guys are right to be leery of patching them with sheetrock and mud. Portland cement and gypsum products are often incompatible. If it is gypsum plaster, they can proceed. I second the votes cast for using setting type mud like Durabond, or Easy-Sand. These are more compatible with plaster than bucket muds, in my experience.
Bugle
P.S. If the plaster is a Portland cement mix, it will be as hard as a rock. Gypsum plaster, while hard, is softer/weaker than stucco.
It works about 80-90% of the time.
Hard Portland will move differently than new mud so cracks can telegraph. But it is nothing to fear.
We make sure the old is clean and sound, then use a bonding agent over the plaster to seal it. Also, I believe that Shewrwin Williams has a paint specially formulated for a primer sealer for this type of application that my finishers have used. We use setting type compound for tying top plaster. Not easy sand. It is a finish product with less binders
There was a long thread a year ago here about the pockmarks and baby cvolcanoes that develope sometimes from skimming over old plaster. I think somebody recommended adding a bit of dish soap to the mud to make it smooth out. Haven't tried that myself. I would lean to using latex admixture for that.
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