How to Fix Sheetrock Scars from Wallpaper

Cover the floor under the damaged wall with plastic tarps to protect its surface.

Locate damaged paper facing that hangs freely from the rest of the wall's paper facing. Pull off those hanging paper remnants with your fingers so the wall surface is flat.

Fill a paint tray with a waterproof, stain-killing primer, and apply the primer to the entire Sheetrock wall using a paint roller. If necessary, use a paintbrush to apply primer in corners and other tight spaces.

Wait for the primer to dry completely to the touch, which typically takes about one hour.

Open a container of joint compound, and scoop up ¼ cup of it using the corner of a 10- or 12-inch broad knife.

Place the knife's blade over a damaged section of the Sheetrock, and spread the joint compound over the area until it is 1/16 inch thick. Repeat the process to apply joint compound to all other damaged areas of the wall.

Wait for the joint compound to dry fully, which usually is about four hours. Aiming a fan at the wall speeds the drying process.

Don a dust mask, and close all doors to the room. Sand the joint compound using fine-grit sandpaper until the entire wall feels smooth when you run your hand over its surface.

Apply a second coat of joint compound to the damaged areas using the same technique you used previously. Do not attempt to build up the joint compound, but simply use it to fill in remaining low spots.

Wait until the joint compound dries, and then sand it using the fine-grit sandpaper.