(c) 2018, Special to The Washington Post Jeanne Huber
The wallpapered walls of my home were painted over with latex paint by the previous owners. Now the seams are showing through the paint. They feel like hard ridges. How can I fix this problem and make the walls smooth enough to repaint - without first having to remove the wallpaper?
You might be able to make the walls smooth enough for new paint without stripping the wallpaper, but you won't know for sure until you can test whether the wallpaper between the seams is securely attached.
It's best to remove wallpaper before painting, according to Cyndi Green, a longtime board member and former president of the Wallcovering Installers Association (wallcoveringinstallers.org) and owner of Cyndi Green Wallcovering Sales & Installations in Monroe, Louisiana (318-348-6908; cgreenwallpapers.com).
But because earlier owners didn't do that, she suggested you start by cutting out one raised seam. Use a sharp utility knife and a straightedge, and slice tidy strips about one-fourth inch out from the seam on both sides. Pry out at least some of the raised material with a thin putty knife. Then, using a broad putty knife, test whether the wallpaper lifts easily.
"It is entirely possible that the paper is not stable now at all and would just strip down completely with the paint," Green wrote in an email. "It just depends on what kind of wallpaper it was." You might find that the wallcovering has a top layer of vinyl that's easy to pull off, or that the whole strips come off easily. In that case, you'd be better off removing the wallpaper and starting over, even though it isn't your preferred solution. But if the wallpaper is 100 percent paper, with no vinyl, the paint may have penetrated it enough so it can't easily be removed, and getting rid of the ridges might indeed be the best option.
To smooth the walls without removing the wallpaper, cut along the raised seams, just as you did the test strip. Clean out the raised bits. Then coat these areas with a primer that seals porous surfaces. This could be an oil-based primer or a water-based product such as Roman Pro-999/Rx-35 Interior Drywall Repair and Sealer Primer ($19.98 at Home Depot). (Be careful not to get the Roman product labelled R-35, without the "x"; it's for nonporous surfaces.)
After the primer dries, fill the recesses you made with drywall joint compound, also known as drywall mud. Use a four-inch drywall joint knife to smooth the patch and level it with the adjoining wallpaper. The patch material will shrink a bit as it dries. The next day, top it with a new layer. Use the drywall knife to feather the edges so you don't create ridges. Once that layer dries, check to see whether the surface is level with the paper on either side. Add a third layer if necessary.
After the final coat dries, you might need a little touch-up sanding. Do this by hand, using a fine-grit sanding sponge or 120-grit sandpaper. Wipe or vacuum all the dust. Then prime the filled areas with a sealer for porous surfaces, such as Roman Pro-999/Rx-35. (Oil-based primer isn't an option this time.) And then, finally, you're ready to repaint.
Why all the focus on which type of primer to use where? Wallpaper adhesives soften when exposed to moisture, and drywall joint compound contains moisture. Sealing the underlying surface first keeps moisture in the joint compound from seeping under the adjoining wallpaper and loosening it. And the primer-sealer on top of the patch keeps it from being more porous than the surrounding painted wallpaper. If the porosity varies, paint dries unevenly, leading to a splotchy look. Not all primers seal out water; you need to prime with a product specifically designed to seal porous surfaces.
If you don't want to do the work yourself, you might consider calling a painter, a drywall expert or a wallcovering installer. Green's advice: If you just want to make the seam ridges flat and then repaint, call a painter. A painter also could add texture to blend in the patches if needed. If you want to start over, a wallcovering installer could identify the current type of wallpaper and would know the best way to remove it, so you could then either repaint or install a new wallcovering.
And if you're not sure how to proceed? Ask a wallcovering installer to visit your home, evaluate your walls and give you an estimate. Estimates are often free, although some companies charge for trip costs, Green said.
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