Hanging or installing a door isn't as difficult as it may seem. Replacing an existing door is easy if the new door core is the same size. Installing a door in a new partition wall is also very easy if you buy a prehung door so you don't have to build the door frame yourself. In fact, you probably can tackle this home improvement project in an hour or two if you have the necessary materials and tools ready.

Measure the old door and opening before purchasing a new door or prehung door system.

Installing a Prehung Door

Prehung doors are the easiest to install. These doors come already set in a frame, and one side of the frame has been trimmed with molding.  Usually, the hardware has been installed, too, making the process even easier.

What You'll Need
Here are the tools you'll want to have on hand to hang an interior door:
  • Prehung door
  • Level
  • Cedar shingle shims
  • Hammer
  • 16d finishing nails
  • Nail set
  • Wood putty
  • 10d finishing nails
  • Wood sealer

To buy a prehung door, you need to know the size of the rough door opening. There are approximately 3 inches at the side jambs and 11/2 inches at the head jamb for fitting purposes. To install a prehung door:

Step 1: Set door into rough opening and vertically level, or plumb, door jamb sides, filling any gaps at top and sides with cedar shingle shims.

Step 2: Nail head and side jambs to rough framing, using 16d finishing nails. Countersink nail heads into face of jambs with nail set. Fill holes with wood putty.

Step 3: Nail finished casing or molding to doorway with 10d finishing nails. Countersink nail heads, and fill with wood putty.

Step 4: Apply wood sealer to both sides of door and top, bottom, and side edges. Seal casing and door moldings, too.