The large, full wall mirrors typically found in bathrooms have a few installation challenges. Unlike smaller mirrors, these mirrors are often cut to fit a space and do not have traditional fasteners. They are also heavier than other mirrors: a mirror that is more than 15 square feet can easily weigh more than a hundred pounds. However, a plain glass mirror is also less expensive than any other type of mirror, making this a popular option for many renovating homeowners.
Use a stud finder to locate and mark with a pencil the position of the studs that are behind the mirror.
Cut a piece of metal J channel to the exact length of your mirror using a hand saw. The J channel should be wide enough to securely fit over the edge of your mirror. Place the J channel against the wall so it can hold the bottom of the mirror in place. Use a carpenter's level to make sure it is level.
Screw the J channel into place using an electric screwdriver, making sure to screw through the metal and into the studs behind the wall. Place a small piece of duct tape over all of the screw heads; this will prevent the screws from scratching the back of the mirror.
Apply mirror mastic to the area of the wall that will be behind the mirror using a caulk gun. Be generous, but make sure that the mastic is far enough away from the edge of the mirror to prevent it from being exposed once the mirror is in place.
Lift the mirror into place, making sure it fits snugly into the J channel. Press the mirror into the wall lightly so it comes in contact with the mirror mastic.
Before beginning this project consider having a mirror custom cut for your bathroom. Just bring the precise measurements of the intended mirror to any glass supply store. Also, be sure to ask about delivery services if the piece of mirror is particularly large. If you would prefer a more traditional looking mirror, consider installing moulding around the mirror once it is on the wall. The moulding can be painted or stained to complement your bathroom; just be sure to mitre the corners for a professional look.
It is important to purchase mirror mastic for this project. A standard construction adhesive will damage the silvering on the back of the mirror, causing marks on the mirror over time. Due to the weight of most mirrors, be sure to ask for help when moving the bathroom mirror and putting it into place.