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Installing a Prehung Door:

Say Goodbye to Mortising Door Hinges

There’s a number of reasons that you might want to install a new interior or exterior door in your home. Is the old one is damaged? Remodeling and adding a new partition with a door? Or is it just time to spruce up the old homestead?

This project isn’t as mysterious as it might seem. This article will guide you through the steps of installing a prehung door.

Easy Door Installation

In the old days, installing a door was a bit more of a tedious process. Today however, a marvelous concept has evolved: the prehung door. Prior to this, a carpenter was usually hired to do the job, which incurred a labor cost.

Today, labor costs have risen but the good news is that a prehung door is easy to install for the average homeowner, saving a wad of cash. All that’s needed is a bit of common sense and a few tools

Tool and Material List

4’ level
Nailset
Hammer
Tape measure
Utility knife
Pry bar
Finish nails
Package of tapered shims (from the door section of your home improvement store)

Buying the Right Door

Door sizes are standardized. If you’re replacing an existing door, measure it. If this is a first time door, the carpenter (or you, hopefully), will have the opening roughed out. Measure the rough opening between the studs and the height of the header. The prehung door jamb will be this size, less one inch or so.

Determine Whether the Door Swings Right or Left

The second thing to be concerned about is the swing of the door, or, which side you want the hinges on, and whether you want the door to swing into the room or out of the room. This is easy.

Position yourself in the doorway on the side, where, if the door were already installed and closed, opening it would make it pass through you (as if you were a ghost). Cross your arms over your chest. Now, as the door swings through you, one of your arms can follow its arc.

Which arm? If it’s your right arm you need a right hand swing door. Otherwise, a left hand swing door.

Installing Your Prehung Door

Remove an existing door door if you have one. Take off the trim and pull the hinge pins to take the door off. Next, remove the jamb using your hammer and pry bar.

Now stand the new door assembly in the opening. The extra space around the jamb is to give you some wiggle room for getting the door assembly plumb in two directions — back and forward and side to side. Also, the top of the jamb has to be level.

Begin with the Butt (Hinge) Side

Start with the butt (hinge) side of the jamb. Check to see that the header is either level or will achieve level when the door knob side is raised. If not, trim the butt side jamb. Holding the level on the inside of the butt side jamb, get it plumb in both the directions mentioned above.

Use your tapered shims between the jamb and the stud (close to the butts), nail through the jamb and shims, but don't sink the nails yet.

Shim under the jamb on the knob side until the header is level. Now, plumb the jamb, shim it, and nail it - top, bottom, and middle. Double check everything for plumb and level again and set your nails with your nailset.

Adding the Final Touches

All that’s left to do now is nail on the trim, cut and install baseboards, putty the nail holes, and install the hardware if it’s not done already. Job well done!