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. 

Spring and fall are the best seasons to apply wallpaper because excessively hot or cold temperatures can cause issues with the paste used to attach the paper to the wall. A professional wallpaper hanger can help you decide if your home is too hot, cold, humid, or dry for the wallpaper to 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.

Hanging wallpaper may seem simple, but in practice it requires significant planning and finesse to make it look professional. To start, you need to get an even application of wallpaper paste across all of your wallpaper, which requires experience and large pasting tables to get right. You also need to plan out your design and match it exactly so that you don’t have imperfections in the finished product. It’s often better to hire a professional wallpaper hanger who can get the job done properly for a clean, smooth finish.