How to Install a Prehung Door

How to Install a Prehung Door. 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.

Install a Prehung Door

One-Piece-Jamb Style

  1. Measure the width and height of your rough opening (i.e with any existing trim and jambs removed) as well as the thickness of the wall.

  2. 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.

  3. Set the door into the opening in your wall and use wooden shims to help center and hold the unit in the opening.

  4. 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.

  5. Drive 6d finish nails partway through the jamb and shims on the hinge side to temporarily attach the unit to the surrounding frame.

  6. Use a framing square to check the other two jamb pieces for square. Also check by closing the door; the gap should be even all around.

  7. Adjust shims as needed, attach all sides of the jamb with 6d nails then trim off the shims extending beyond the door.

  8. Install the casing molding to the outside of the frame with 4d finish nails.

  9. 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

  1. Install the jamb half that has the door attached just as you would a standard prehung door. (See above.)

  2. 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.

  3. Countersink all nail heads with a nail set and fill holes with wood putty.

  4. Stain or paint to suit your taste.

  5. Tip

    Make sure not to use interior doors for exterior purposes. They are neither secure nor weatherproof. The wooden shims need to completely fill the gap between the door jamb 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. YOU may need to overlap two or even three shims to get the proper thickness A split jamb can be helpful in hiding out-of-square door openings and walls that lean.


    Some doors come with doorknob and lock sets, while with others you'll have to purchase all pieces separately.