Is There Any Way to Seal Damage to a Plaster Wall After Removing Wallpaper Before Painting?

A skim coat can repair most imperfections in a plaster wall.

Wallpaper can hide many imperfections on older plaster walls. In addition, removing wallpaper can create many imperfections on plaster. In many cases, when it comes to home construction, plaster is a coating that goes over wood lath or brick. Over time, plaster deteriorates and develops hairline cracks and pits that paint cannot hide. You can repair your plaster walls by using a process called skim coating. Skim coating allows you to resurface the walls with new plaster, which covers up imperfections in the wall.

Things You'll Need

• Wire brush
• 400-grit sanding block
• Pole sander (optional)
• Plastic bucket, 5 gallon
• Plaster
• Trowel
• Floor lamp
• 600-grit sanding block
• Tack cloth

Instructions

1. Remove loose plaster from the wall with a wire brush. Removing larger pockets of loose plaster ensures the new plaster adheres to the wall.

2. Sand the surface of the wall with a 400-grit sanding block or sanding pole to scuff the surface of the wall and to remove wallpaper residue, which could prevent good adhesion of the plaster.

3. Mix a five-gallon bucket of plaster with a trowel, then apply a moderate mount of plaster to the trowel that covers approximately 75 percent of the trowel's surface.

4. Hold the trowel at one end of the wall with the edge of the trowel butting up against the ceiling. Gently run the trowel in a straight line across the wall, distributing the plaster onto the wall in a 1/8-inch layer. Work to keep the layer as flat as possible. Apply more plaster to the trowel as needed to complete the first row.

5. Add more plaster to the trowel and complete the second and each additional row as you work your way down the wall. Overlap each row by 50 percent to ensure adequate coverage and help minimize lines between strokes. Work to keep the wall as flat and even as possible while filling in imperfections in the surface of the wall. Allow 48 hours of drying time before moving on.

6. Place a floor lamp without the lampshade next to the wall to illuminate the surface of the wall. The lamp shows shadows where you still have imperfections in the wall, such as waviness.

7. Sand the surface of the wall with a 600-grit block sander or pole sander to smooth the surface of the new plaster. Focus on waves in the wall. Keep looking down the length of the wall to see where the light shows shadows. Continue to sand until you have removed, smoothed and leveled the wall.

8. Wipe the wall down with a tack cloth to remove any sanding dust before you paint the wall.

Tips & Warnings

• It takes time to apply the plaster and sand the wall. Expect your first attempt to take longer until you perfect the process. You may eliminate some of the skill required by rolling over the wet plaster with a lamb's-wool roller to create a "knock" down" or "stippled" effect to your wall. This texture hides imperfections and you can paint over it.

References

• Painting and Decorating Concourse: Drywall Surface Preparation: Skim Coating