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. 

In most cases, it is not recommended to wallpaper over existing wallpaper, as the success depends on the type of paper already on the wall. While you might be able to cover non-coated wallpaper, you should never apply new wallpaper over a vinyl-coated one, which is more common. Doing so can lead to poor adhesion, resulting in bubbles, imperfections, and peeling. It can also trap moisture, potentially causing hazardous mold growth between the layers.

Even if the existing wallpaper is suitable, experts recommend applying only one new layer. Adding multiple layers (more than two total) can cause significant adhesion problems, leading to warping and bubbling. For the best results, the recommended approach is to remove the old wallpaper and all paste residue before hanging the new paper. If you are unsure about your wallpaper type, consider consulting a professional.

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.

Rubbing alcohol may help dissolve stubborn wallpaper adhesive that remains after removal, but be sure to apply it carefully to prevent damaging your walls. Apply a small amount using a cotton swab or pad, then gently scrape or wipe the adhesive away.