Plaster Won’t Adhere to Drywall
LESLIE: Robert in Oregon is on the line and is having an issue with some plaster walls at his home. How can we help you?
ROBERT: Well, I was (inaudible at 0:13:12) room in my bedroom and after applying the plaster, some of the plaster was coming off after I painted it. But originally, I did the living room, which was my first job, and I mixed it – a bunch of the plaster – Imperial plaster. And of course, I mixed too much and it got hard, you know? So I learned not to mix so much, because it only – you can only use so much during a certain time, you know, before it sets up.
So, anyway, in the next room, I drywalled it, finished it and then I used a product called Plaster-Weld, which is supposed to be a primer for the plaster.
TOM: Right. Plaster-Weld is a bonding agent.
TOM: And you used this on top of drywall? Is that correct?
TOM: Was it new drywall?
ROBERT: Yeah, new drywall.
ROBERT: But I’d primed the walls first and then put the Plaster-Weld over that.
TOM: OK. Hmm. OK.
ROBERT: And then mixed up my plaster – it was Imperial plaster – and applied it and finished it all up and troweled it to the texture I wanted. And then we went back – my wife and I – and touched up a few spots and then let it dry overnight. Then we put a primer on it and while putting the primer on it, some of the plaster was coming off.
TOM: First of all, I would not have primed the drywall. I don’t really see a reason to do that. You prime the drywall to control adhesion and to stop the absorption, I should say, of the new paint – the top coat of paint – and to get an even sheen. But you weren’t really concerned about sheen because you intended to do a plaster coat.
You were basically building what’s called “plaster lath.” This is the way homes were done in the 50s, where you have a drywall base and then you put a plaster coat on top of that. The bonding agent was the right thing to do but that should have gone directly onto the drywall. Now you put the drywall on and then you put a primer over that and then you put the bonding agent on top of that. So now you have to get the bonding agent to stick to the primer and that’s a little more difficult than getting it to stick to the raw drywall.
So I think you’ve got a situation now where you’re going to have this problem potentially repeating itself. So I hate to tell you this but what I might do is put another layer of drywall over this – real thin layer – and start again. You don’t have to use ½-inch; you can use ¼-inch just to skim it. And then put the plaster over that.
ROBERT: Alright. Thanks.
TOM: You’re welcome. Thanks so much for calling us at 888-MONEY-PIT.