How to remove old wallpaper without damaging plaster walls

Why old wallpaper on plaster needs a gentler approach than drywall

Plaster and drywall react very differently to water. Drywall has a paper face that swells and tears when it gets too wet, so the main risk there is soaking through the face. Plaster tolerates water much better, which is good news for removal. The risk with plaster is mechanical: the finish coat on a hundred-year-old wall can be softer than it looks, and a sharp scraper or a stiff scoring wheel will dig into it.

Many rooms in Wollaston two-families, North Quincy triple-deckers and the older Colonials in Milton and Dedham have more than one layer of paper, sometimes three or four, with paint between some of them. Older papers were often hung with wheat or starch paste, which softens with warm water. Later papers may have been hung with stronger vinyl adhesives. Each layer comes off a little differently, which is why we always start with a test patch before committing to a method.

How to test a corner and figure out what kind of wallpaper you have

Pick a spot behind a door or near a corner and try to lift a seam with a fingernail or a putty knife. If the face peels off in a big sheet and leaves a paper backing on the wall, it's a strippable or peelable vinyl, and the backing comes off with water afterward. If nothing peels and water beads on the surface, it's a vinyl-coated paper or a painted-over paper that needs its surface opened before water can get through.

If the paper soaks up water and goes dark, it's an uncoated paper, the easiest to remove. Also note what is under it. If you see a shiny surface, the wall may have been painted with oil paint before papering. If you see chalky white plaster with no paint at all, the wall was never sealed, and the old paste may be stuck straight to the finish coat.

• Face peels dry, backing stays: strippable or peelable vinyl
• Water beads on the surface: coated, vinyl or painted paper
• Water soaks in and darkens: uncoated paper, easiest removal
• Several layers visible at the edge: plan for more time per room

When scoring helps and when it gouges the plaster

Scoring tools with spiked wheels punch small holes in the paper so water can reach the paste. On a coated or painted paper, some kind of perforation is often needed. The problem is pressure. Pushed hard into old plaster, those spikes leave hundreds of tiny pits that all have to be filled before the wall can be painted or repapered.

We use a light touch, letting the tool roll over the surface with almost no weight on it, and we test that first in a corner. On many coated papers, a better option is to sand the face lightly with coarse sandpaper by hand or to peel the vinyl layer off dry, which opens the surface without touching the plaster. In a pre-1978 house, which covers nearly every older home in Quincy, any sanding of a painted surface is treated as possibly lead painted and done with dust control.

Steam versus remover solution on old plaster

Both work, and the choice depends on the paper. A solution of warm water with a little dish soap, a fabric softener or a commercial enzyme remover is enough for most uncoated papers and backings. Apply it with a garden pump sprayer or a sponge, let it soak 10 to 15 minutes, and scrape. Re-wet the area if the paper starts to dry. Work in sections about the size of a single strip so the solution doesn't dry before you get to it.

Steam is better for multiple layers, papers painted over with latex, and stubborn older pastes. A wallpaper steamer plate held against the wall for 20 to 60 seconds softens the paste behind it. It's slower but very effective. On plaster, steam is safe as long as you don't hold the plate in one spot long enough to loosen weak plaster keys. Wear gloves; steamers and the wet paper get hot. In a humid summer near Quincy Bay, open a window or run a dehumidifier so the room doesn't stay damp for days.

How to handle painted-over wallpaper on a plaster wall

Paper that has been painted over is one of the most common finds in older Quincy and South Shore houses, especially in rental units where a quick coat of paint went over the paper at a past turnover. It's also the hardest to remove. The paint seals the paper so water can't get in, and sometimes the paint has also glued the seams down. The first step is to break that surface, either by lightly scoring, hand sanding or carefully cutting through the paint at the seams.

Steam usually works better than solution on painted paper, and it may take two passes. In some cases, the paper is tight, sound and adhered across the entire wall, and the better choice is to leave it, seal it with an oil or shellac based primer, and skim coat over it. That avoids hours of scraping and the risk of pulling up chunks of plaster with the paper.

How to clean off sizing and paste residue and prime the bare wall

Once the paper is off, the wall isn't ready yet. Old paste and sizing, a thin sealer brushed on before papering, leave a film that feels slick or tacky when wet. Paint over that film and it can crack, wrinkle or peel later. Wash the walls with warm water and a sponge, changing the water often, and keep going until the surface no longer feels slippery. Some walls need two or three washes.

Let the plaster dry completely, usually 24 to 48 hours in a heated room, longer on a cold exterior wall in winter. Then fill any gouges and cracks, and prime the whole wall with an oil or shellac based primer. Those primers seal in any remaining paste and keep it from reactivating under water-based paint. Skip the primer and you may see bubbles or cracks within days.

• Wash until the wall stops feeling slippery
• Dry 24 to 48 hours before patching
• Fill gouges and cracks with a setting-type compound
• Prime with an oil or shellac based primer before painting