In general, removing wallpaper from your walls before painting will provide better quality and longer-lasting results than simply painting over it. Before deciding to remove your paper, here are some things to consider.
Wallpaper is generally applied in rows, so when it's painted over, the seams where these rows line up will often show through the paint. In addition, most wallpaper is textured, some quite noticeably, and the patterns and textures in the paper may show through the paint. Finally, the moisture in the paint can loosen the wallpaper's adhesive, causing sections of the paper to bubble or detach from the wall [source: Austin].
Of course, there are potential problems to removing wallpaper. First, the work may be difficult and time-consuming, depending on how and when the paper was applied. Those with older homes may find half a dozen layers of paper or more, and each one will likely be more difficult to remove. Finally, there's the potential for unexpected surprises once the paper is removed. The drywall or plaster underneath could be crumbling or damaged, with the wallpaper being the only thing that has held it together up to this point.
Paper that's loose, ripped or has holes should always be removed before painting, as these are signs that the paper is beginning to fail. By painting over it, you're investing effort and money into a project that won't last.
Finally, consider your future plans for the space. Wallpaper that has been painted over is notoriously difficult to remove [source: Thomas]. While it can be removed with a lot of extra effort, you will likely remove sections of drywall or plaster with the paper. If you plan to stay in your current home for a long time, you'll be better off in the long run if you simply remove the paper now instead of creating problems for yourself down the road.
There are many methods available for removing wallpaper and prepping your walls for painting. For an overview of these methods, check out this article on How to Remove Wallpaper. Remember to remove one layer at a time to avoid damaging drywall or plaster.
Read on to the next section to learn how painting over wallpaper may be your best option in certain scenarios, and how to ensure you get good results.