Double entrance doors are usually heavier than their inner cousins. Many new homes will have 2-of-6 exterior walls, so the jamb is wider; make sure to check out. They can also be made of a half-inch layer versus 3/4 inch typically of internal side pieces. To make the job as simple as possible, start with a prefabricated jamb kit, which comes with a doorstep casting attached and side jambs hack to receive the head. Brick mold can be purchased in ready-made batches to fit the width and height of your door for all 80-inch high doors.
Cut the jamb header to the length, 1/4 inch wider than your double entrance doors, using a power saw. Mount three pieces of jamb frame by gluing and nailing the horizontal jamb header into the slots in the vertical side jambs using 16d frame nails. Attach the three parts of your pre-cut brick mold to the outside of the jamb frame. The two vertical side posts should be set with 45 degrees of miters at the top. Fit tops that are intersected at both ends, between them to adjust vertices for placement on the jamb. Spike the shape in place with 2-inch surface nails placed every 12 to 16 inches.
Measure the inner dimension of the side frame directly below the head and adjust the legs of the double entrance doors frame so that the distance between their lower ends matches it. Attach the prefab sidearm the threshold to the bottom of the side zip using a 08/05 inch treated tire screws. Lay the door inside the side frame with its upper edge 1/4 inch below the lower surface of the side arm head. Mark hinges positions 1 foot down from the top and up from the bottom and in the center of the door in the face of the door and in the same position on the edge of the jamb. Remove the door from the frame.