You must remember that your wallpaper is glued to a flat surface. Any kinds of unevenness or roughness may cause your self-adhesive wallpaper not to stick well, and there will be air remaining in the gaps, which may not show up immediately but will cause the wallpaper to peel away over time.
It is also important that the wall has a preserved vertical because this unevenness may cause the pattern not to match the joints. It is also recommended to avoid sticking directly to a gypsum board.
If you install wallpaper on a wall covered with paint, be sure to wait at least three weeks after the last coast and to ensure it has fully dried.
