Your bathroom is not the most ideal place to have wallpaper, because the typical bathroom is the most humid room in a home. Running a hot bath or taking a hot shower will make the entire bathroom steamy and filled with moisture. When this moisture settles on the wallpaper, it can do some damage or allow the wallpaper to peel away or sag from the wall. In general, wallpaper all over your house should be protected, but this is especially important when it comes to the wallpaper in your bathroom.
Apply one coat of decorator's varnish to the wallpaper in your bathroom, using a standard paintbrush. This product helps to protect against moisture issues. Tape off any trim or other areas around the wallpaper with painter's tape to protect them before you begin. Use broad, long strokes, starting from the top and working your way down the wallpaper.
Avoid splashing water from the tub or shower onto the wallpaper. This can usually be accomplished by keeping the shower curtain closed at all times.
Calculate the size of exhaust fan you should have in your bathroom. This is determined by the number of room air changes needed per hour, or ACH. To find the ACH, you first need to calculate the volume of your bathroom by multiplying the length, width and height. Then, multiply the volume by 20 to get the ACH. When you select an exhaust fan for your bathroom, look for one that offers the right amount of air changes per hour, or ACH. Manufacturers will list this information in the product description for the exhaust fan.
Run the exhaust every time someone takes a shower or bath in the bathroom. Keep it running until the mirrors are no longer fogged to help protect your wallpaper from moisture.