Repair Cracks in Plaster Walls
LESLIE: Calling from Illinois, we’ve got Sue whose home is cracking up. What can we do to help?
SUE: Hi, yes. (chuckles) Well, I’ve done – I have a 200-year-old house and, as you might guess, I’ve got a lot of plaster walls. I applied skim coat to most of the cracks about seven years ago and they’re back. And I want to know what else I can do. One specifically, upstairs in the hallway, goes vertically from essentially just the roofline all the way down to the baseboard and that one actually has a little bit of a bow to it. So that scares me more than anything else.
TOM: Sue, if there’s a bow to it, what’s happening is the plaster is separating from the lath behind it and there’s not going to be an easy correction for that. That is the plaster deteriorating and the option is really to skim that wall with another layer of drywall or to break off the loose plaster and then replaster it.
Now the solution for the cracks is different. When you just do a skim coat on top of that, that plaster that you put on top is not elastic so it’s not going to expand and contract with the old crack. What you need to do is use a piece of fiberglass drywall tape that looks sort of like netting. It’s perforated and you apply that to the crack first and then you spackle on top of that or plaster on top of that two or three layers and that is going to adhere enough where the wall can expand and contract without the crack showing through. But just to put more plaster on top of the cracked plaster is not going to solve it. The same way it’s difficult to solve with a cracked sidewalk. Anything that moves like that has to have something in it that’s elastic and very sticky and if you use the tape that’ll solve it.
SUE: Actually, I did use the tape.
TOM: You did use the tape? Well …
SUE: I did.
TOM: OK. Now did you use paper tape or fiberglass tape?
SUE: The fiberglass.
TOM: Well, let’s just review how you did it. Did you sand the wall to get rid of all of the old paint first?
SUE: Hmm. (Leslie chuckles) Probably not. (chuckles)
TOM: Because that could be like a layer of grease in between the tape and the wall …
LESLIE: And could cause that tape to slip right off as soon as there’s any movement.
TOM: So that’s probably what happened. That is the solution and if it’s sanded – remove the old paint; there’s nothing loose underneath it and then put the tape back on there. You’re going to have to pull the old repair out now, by the way. But just do a good job sanding that and that should cover it. Now if the bulge is not too bad, you may want to try to spackle over that. And on a wall we’re not as concerned as when you have a bulge in the ceiling because that plaster can actually fall; it’s pretty darned heavy. Don’t ask me why I know; I just do. (Leslie and Sue chuckle) And it can hurt you. (chuckling) OK?
SUE: Yes. (chuckles) OK, very good. Thank you.
TOM: Alright, thanks so much for calling us at 888-MONEY-PIT.