Painting over your wallpapered walls can be a great way to change the look of your room. In many older homes, the walls were covered with wallpaper; if it has been on the walls for a long period of time, the wallpaper can be very difficult and time-consuming to remove. Instead of taking the time to strip the walls, why not just paint over them? There is a little prep work that needs to go into this, but in the end you will have a great looking wall that nobody will ever know had wallpaper on it.
Preparing the wall
Glue down any loose pieces of wallpaper or seams that have lifted. Wallpaper seam glue works very well for this. If you have large pieces that are peeling, pull those off rather than gluing them down.
Prime the entire wall with a fast-drying shellac or alcohol-based primer, using a roller. Be sure to ventilate the room very well or wear a respirator while working with the primer or shellac.
Apply joint compound to all the seams. Use a drywall knife or putty knife to lay down the joint compound. A wider knife is better because you want to spread the joint compound very wide, feathering in the edges to help hide those seams.
Allow the joint compound to dry for two to three hours before sanding. Thin coats of joint compound with dry a little faster with less shrinkage of the material, making this process faster.
Sand the joint compound with a sanding sponge, removing any high spots in the seam. These are available at most paint stores and create less dust and debris during the sanding process.
Painting the wall
Coat the entire wall in a coat of drywall primer. The primer can be applied just like paint with a roller or brush. This will seal and protect the wall, allowing the paint to adhere and not soak into the paper.
Paint the wall with a smooth roller, cutting in the corners with a small paintbrush to avoid getting paint in unwanted areas. It may take several coats depending on the color of the paint and the color of the paper below it.
Paint the wall with additional coats as required. This is completely cosmetic, so apply as many paint coats as needed until you are happy with the results.