No, not all wallpapers are waterproof. Wallpapers made of vinyl or non-woven materials and are coated with a protective layer to prevent water from seeping through are typically made to withstand humidity and moisture. They are often used in areas such as bathrooms and/or kitchens where traditional wallpaper may not be suitable. However, it's important to note that even with waterproof wallpaper, proper ventilation and maintenance are still necessary to prevent the growth of mould and mildew.