Here is a handyman tip that demands safety. Removing a bathroom mirror from a wall certainly doesn't look intimidating. In fact, the mirror can look as if it is held to the wall with a few fasteners. Easy right? Not so much. Most likely the mirror has been glued to the wall, and when I say glued, I mean the wall will come down along with the mirror.
The mirror gets glued to the wall with mirror mastic or other suitable adhesive. Usually, you will find large globs of adhesive behind the mirror. For this reason, you will have drywall repair to do after you remove the mirror, or you might decide to cover the damage with a different mirror.
At the minimum, safety goggles and gloves are mandatory. If you are lucky, the mirror will slowly peel off of the wall without breaking. By the way, the larger the mirror, the more help you need to get it off in one piece.
I use a stiff putty knife 3-4 inches wide. The stiffer the better. I also use a long standard screwdriver. Start by inserting the putty knife behind the mirror and gently lifting. When the mirror starts to lift, insert the screwdriver in and continue to pry the mirror. As you lift the screwdriver, move the putty knife over a few inches and push it behind the mirror and gently lift. Slower is better here. You should hear the drywall paper tearing as you lift. Do this slowly. The goal here is to remove the mirror in one piece so that you are left with repairing the drywall. The last thing you want to do is to lift to aggressively and break the mirror. Not only will you damage the sink, floor, etc., you may also injure yourself. Be careful on this job and go slowly!
Adding a mirror to a bedroom door makes a lot of sense. You can make it as big as the door, or nearly so, and see yourself from head to toe. The only caution is to make sure the mirror is secured sufficiently enough to the door not to break.
Installing the mirror to the door will depend on what type of mirror you buy. Some framed mirrors are sold with the specific intent of mounting to a door. This style of mirror is lightweight and can be mounted to the door with screws and adhesive. Make sure if you are using screws that you are screwing into some solid material. Installing a screw into a hollow core door will not hold. Screwing into a solid core door will offer more meat for the screw threads to bite into.
I would use a lightweight mirror and use adhesive and clips to mount it to the door. You can buy mirror clips at any home center. They are shaped like the letter “L” and have a groove that the mirror slides into. As you tighten the clip it clamps down on the edge of the mirror. These clips combined with adhesive should make for a lasting hold.
Kids like to throw things right? Would you like to guess what happens when your child throws a shoe at your mirror? That's right. You get to replace the mirror.
Removing a broken mirror can be dangerous. They are sharp and additional pieces can fall off of the wall and shatter while you are working on or around them. Always use gloves and eye protection when doing this. After removing what's left of the mirror on the wall, you will likely have some drywall holes...in some installations hot adhesive is used and removing the mirror can leave some holes in the wall. You can certainly do some drywall repairs, but they don't have to be pretty as you will be covering up the area with the new mirror anyway.
You can use mirror mastic to glue the mirror to the wall. This is sold in tubes and fit into a caulking gun. Basically, you will lay down some thick beads of the mirror mastic and push the mirror to the wall. If you aren't using any other type of fasteners, it would be a good idea to tape the mirror to the wall until the mastic sets up and reaches its full holding strength.
Some mirrors sit in a track which will help hold it, and still others have clips around the perimeter. The more methods to hold the mirror in place the better.