If you’re installing new wallpaper and have leftover glue, you can remove unused wallpaper paste from the bucket or pan it’s in by letting it dry. If it’s an oil-based paste, seal it in a plastic bag and throw it in the garbage. Otherwise, toss the leftover wallpaper paste in the trash. Although it’s water-soluble, don’t rinse unused wallpaper paste down the sink because it could dry in the pipes and cause a blockage.

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. 

The average cost to remove wood paneling is $2,800, but total costs may be higher or lower depending on the size of the room, your location, and the amount of prep work required. Once the paneling is gone, you may have additional costs depending on the condition of the wall beneath.

The average cost to install or hang wallpaper is around $575 per room or project, with typical prices ranging from $200 to $1,500. Costs can be higher for custom or luxury products. Since project size varies, it's often helpful to estimate labor costs per square foot, which generally fall between $1 and $7, with an average of $4 per square foot. The total cost depends on several factors, including the quality and type of wallpaper, the size and type of the room, and whether old wallpaper must be removed first. Opting for less expensive materials like peel-and-stick wallpaper or choosing to do the installation yourself can lower the overall cost. For the most accurate estimate, it is best to have a professional inspect the space and provide a quote.