Many peel-and-stick wallpapers aren’t moisture-resistant, so if you install them in high-humidity rooms, mold can grow behind the wallpaper. It’s best to reserve peel-and-stick wallpaper for bedrooms, living rooms, and other rooms with lower humidity levels. Not only does this minimize the risk of mold growth, but it also keeps the wallpaper from bubbling or peeling.

No, you don’t always have to remove old wallpaper before applying a new layer. However, you should pull off the existing wallpaper if it’s cracked, peeling, or in poor condition. We’d also recommend against putting wallpaper over textured or dark-colored wallpaper because the old layer may be visible through the new one. In addition, if you try to hang new wallpaper over vinyl-coated wallpaper, the adhesive might not stick properly. 

Wallpaper lasts an average of around 15 years, but there is some variance. The type of wallpaper matters, as vinyl wallpaper tends to last the longest—sometimes 20 years or more—while a peel-and-stick wallpaper, which is the easiest to install for DIYers, will usually only last for around five years. Exposure to high humidity, smoke, and UV rays from sunlight can also limit the lifespan of your wallpaper, as can heavy traffic in the installation area.

Costs depend on wallpaper type, wall condition, labor, and necessary repairs.