Painting over wallpaper is something you can do successfully. We remove lots of wallpaper and occasionally put up new. Sometimes removing wallpaper is more trouble then it’s worth. In that situation we suggest painting over it.
To be able to paint over your wallpaper it must be tightly bound to your walls. If the wallpaper is tightly bound to the wall the the next step is to clean the paper. a damp cloth and a mild laundry detergent works well. I like Dawn dish soap. Be sure to rinse the walls using a clean damp cloth. It is important to not over saturate the walls with water or you may have a problem with how well the paper sticks to the wall.
The next step is to prep the walls for painting. Tape off the base, remove stitch plates, etc. You will want to use an oil base primer over the wallpaper. We do two coats. After priming you will want to look at the paper for any open seams, tears, on the wallpaper. These imperfections will need to be skim coated with drywall mud. After drying you will sand smooth and re-prime those areas.
Now you should be ready for the finish coat. If you notice any bubbles that rise up in the paper, they will need to be cut out, have mud applied and sanded, then primed. Sometimes you can get all the way to the finish coat before bubble form. Just cut them out and mud.
Two coats finish are best. Painting over wallpaper isn’t hard at all.