Buying a prehung door, in which the door comes already hinged to the framed-up door casing, is a little more expensive than buying the door, jamb and trim separately, but finished, professional-looking results are so much easier to achieve.
Measure the width and height of your opening and the thickness of the wall.
Step2
Take these measurements to your local home improvement center or lumberyard. Pick out the appropriate size of door needed and the style that suits your taste.
Step3
Set the door into the opening in your wall and use wooden shims to help center and hold the unit in the opening.
Step4
Be sure to completely fill the gap between the door frame and stud framing where the hinges and lock set will attach so that you don't warp the door frame as you put the screws in. Wood shims, either purchased or homemade, do the job nicely.
Step5
Adjust the door using a carpenter's square and a level until it is as close to true and as plumb as possible. Use the shims to level and hold the door in place.
Step6
Drive 6d finish nails partway through the jamb and shims on the hinge side to temporarily attach the unit to the surrounding frame.
Step7
Use a framing square to check the other two jamb pieces for evenness. Also check by closing the door; the gap should be even all around.
Step8
Adjust shims as needed and attach all sides of the jamb with 6d nails.
Step9
Install the casing molding to the outside of the frame with 4d finish nails.
Step10
Countersink all nails with a nail set and fill holes with wood putty. The door is ready for staining or painting to suit your style.
Split-Style Jamb
Step1
Install the jamb half that has the door attached just as you would a standard prehung door. (See above.)
Step2
Slip in the second half of the jamb from the opposite side of the door and cover the joint between the two with the stop molding provided.
Step3
Countersink all nail heads with a nail set and fill holes with wood putty.
Step4
Stain or paint to suit your taste.
Tips & Warnings
Make sure not to use interior doors for exterior purposes. They are neither secure nor weatherproof.
Some doors come with doorknob and lock sets, while with others you'll have to purchase all pieces separately.
A split jamb can be helpful in hiding out-of-square door openings and walls that lean.