Before you rush out to buy the supplies to hang a mirror on the back of a door -- closet, bedroom or bathroom -- examine both the door and mirror. The door's construction -- solid or hollow core -- along with its finished appearance, paneled or flush, plays a significant part in the supplies needed to attach the mirror to the door.
Frameless mirrors require special clips to hold the mirror in place, unless you have a flush door with no raised panels or boards and want to glue it in place instead. For framed mirrors, the fasteners required depend on the door's construction. Some mirrors come with special hangers that fit over the top of the door; these doors require no hardware except a screwdriver to adjust its position, but these are typically more expensive models.
Mounting a framed mirror on a hollow-core bathroom, bedroom or closet door involves the same steps regardless of the door.
Measure the door's thickness to ensure that the miniature molly bolts or toggles fit inside the door's dimensions. Add the depth of the mirror's frame to this measurement to ensure the miniature molly or toggle bolt fits through the mirror's frame and the door's panel, which is generally 1/4 inch thick.
Weigh the mirror to get the molly or toggle bolts rated for the mirror's weight. Most miniature molly bolts can support from 20 to 50 pounds; you'll need at least four molly bolts to secure all four corners of the mirror so that it doesn't bump against the door and break when opened or closed.
Hold the mirror up to the door to mark its placement on the door with a pencil. Run the pencil at least 1 inch around all four corners of the mirror, two marks per corner. This helps you select the spot to insert the molly or toggle bolts in each corner of the mirror. If you have a door with raised panels, aim for mounting the mirror on crosspieces. Mark the spot on the door where you plan to drill and transfer those same marks to the mirror, so that the holes will line up.
Drill through the hollow core door only the thickness of the panel, which is generally 1/4 inch thick or so. Drill holes in the mirror at the designated spots.
Hold the mirror up to the door and insert the molly bolts through the holes. Secure them by screwing them. As the screw turns, the housing of the molly bolt pulls up against the door and locks the screw inside the panel to prevent it from pulling out. Repeat for all four corners of the mirror.
Specialty mirror clips that grasp the mirror will hold it in place against the door. Count the number of clips needed to securely hold the mirror to the hollow core door. For clips, mount them on the mirror first. If you use brackets, mount the brackets on the door and slide the mirror into the brackets.
Install the clips on the mirror..
Hold the mirror against the door and make a mark with the pencil through the screw hole in the clip.
Follow Steps 4 and 5 from the previous section to install the miniature molly bolts and mount the mirror.
To mount mirrors on solid core-doors, follow the steps for mounting mirrors on hollow-core doors, eliminating drilling holes for molly bolts. Instead, use the drill to create a small pilot pole in the mirror and the door. Insert a screw bit into the drill and secure the screw to the door after inserting a countersunk finishing washer on it. The countersunk washer keeps the mirror from pulling away from the screw.
Best practices call for gluing frameless mirrors to flush doors. While you can glue a framless mirror to a paneled door, the chances of someone putting his elbow accidentally through the mirror and breaking it increase when the mirror is glued to the raised areas of the door. Remove the door from its hinges and lay it flat on the floor or a work surface so that you don't have to support the mirror as the glue dries.
Clean the door and the back of the mirror thoroughly to ensure it is grease- and dirt-free. After cleaning, wipe down the door and back of the mirror with rubbing alcohol to remove any remaining residue. Hold the mirror to the door and outline its four corners to you know where to install it after adding glue.
Squirt a 1-inch spot of glue for every square foot of mirror onto the back of the mirror. Position the mirror to line up with the pencil marks you made and press the mirror against the door. Clean up any glue that squeezes out between the door and the mirror. Rehang the door after the glue has cured, which can take up to 48 hours, depending on the glue manufacturer.