Changing wall colours in your home can change the entire look of your room, but when wallpaper covers the wall, your options are to remove the old wallpaper or paint over it. Removing old wallpaper can damage the drywall or plaster if it was not properly installed. As long as you prepare the old wallpaper correctly, painting over the old wallpaper is possible.
Wash the wall surface with a gentle cleanser to remove any dirt, grease or grime. Wipe the wallpaper with a dry towel and let the surface dry overnight.
Go over the wallpaper to look for any imperfections. Use white glue or wallpaper adhesive to glue down any loose areas of wallpaper. Use a plastic putty knife to spread a thin layer of joint compound along all the seams, fill any nail holes, and cover any damaged areas. Allow the joint compound to dry for three to four hours.
Sand the joint compound with 220-grit sandpaper to smooth the surface before painting. Run your hand over the wall to check for any rough surfaces you missed.
Tape off any areas with painters tape that you do not want painted. Remove the screws from the switch and outlet plate covers to take them off the wall.
Apply an oil-based stain-blocking primer over the wallpaper with a paint roller. Allow the first coat of primer to dry for one hour before applying the second coat. Allow the second coat of primer to dry overnight.
Paint over the primed wallpaper with a latex-based paint using a paint roller. Allow the first coat to dry then apply the second coat of paint to the wall. Allow the paint to dry overnight and replace the switch and outlet plate covers.