How do I repair lifted plaster skim coat?

dwpcDecember 7, 2012

For some unknown reason, our 1972 house has some rooms with 1/4" hardboard (e.g. common brown Masonite) interior walls covered with a plaster skim coat. The 1/8" or so skim coat was a quality job and nicely textured, so we don't want to rip the hardboard down and sheetrock it. However, since the hardboard and plaster expand differently, there are several narrow (3/4") areas along the hardboard butts where the skim coat has cracked at the seam and lifted from the backing just enough to be noticeable. If pressed back down, they virtually vanish. But how can I do it permanently?

Can anyone recommend a quick-acting non-water-based glue I could inject via syringe under the lifted skim coat that would secure the plaster to the hardboard? The problems are 1) a water-based glue may soften the skim coat and defeat the idea, and 2)there's no effective way to keep pressure on the affected areas for a common glue to set.

This issue extends a few ft here and there over about 20 ft of seams total. I'd like to avoid a big spackling job by busting out the lifted stuff. It would also be difficult to match to the existing wall textures. And I also have a hunch that spackling these areas will just cause more lifting as the moisture in the compound will soften the adjacent skim coat.

Here is a link that might be useful: These are the glue syringes I'd use

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akamainegrower

Any butt joint without reinforcing tape of some kind installed prior to a skim coat will fail, usually pretty quickly. Masonite is especially unstable so it's somewhat surprising that more seams have not opened up.

If you really want to try gluing, I'd opt for cyanoacrylate - aka super glue in the gel form so that it does not run excessively. Non-water containing and sets up fast enough so that a simple brace or even hand pressure would be all that's needed.

Not that it makes a great deal of difference, but are you sure the skim coat is actual plaster and not joint compound? I also hate to be pessimistic, but you'll likely have continuing problems with these joints.

    Bookmark   December 8, 2012 at 6:00AM
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dwpc

I think its plaster because it was textured and the pieces that I broke off seemed less chalky than dried compound. I thought of using regular liquid cyano glue so I can inject it; there's no other way to get under skim coat as the cracks are pretty tight. The lifting looks like an old wallpaper seam (that's what I thought it was when I first saw it). I planned to drill small holes for the injector. Any experience using cyano gel or liquid in a plastic injector syringe? They're not cheap so I'm hoping someone has tried this.

    Bookmark   December 8, 2012 at 12:34PM
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brickeyee

"I think its plaster because it was textured and the pieces that I broke off seemed less chalky than dried compound."

Throw the piece in a glass of water and see if it soften up.

Pre-mixed drywall compound will turn back into paste, setting compound and plaster will just sit there pretty much unaffected.

    Bookmark   December 8, 2012 at 1:27PM
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akamainegrower

I have never used cyano glue for wall repair, but have for other things. You really don't need a syringe. A squeeze-able bottle and a length of teflon tubing are all it takes. If the cracks are really tight, you'll probably better off with thin glue - this means quicker set up time, too. Hobby stores usually have the teflon tubing for model makers because it fits into the glue bottles and cyano won't stick to it. The cyano in small bottles is generally very expensive compared to that which is available from Rockler and other sources for woodworkers. They may have the tubing as well.

    Bookmark   December 9, 2012 at 8:45AM
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