How to Install Pre-Hung Exterior Double Doors

The successful installation of an exterior pre-hung double door unit is a matter of insuring the unit is held plumb and square as it is secured in placed. With this methodical approach, the doors will provide long years of use and functionality for the home.<br /><br />Pre-hung double door assemblies are heavy and cumbersome to maneuver. It is recommended that you enlist the assistance of a helper during the work. Be sure to follow all manufacturer’s specifications in the handling and installation to maintain the product warranty.

Things You'll Need

• Measuring tape<br />Pencil<br />Pry bar<br />Hammer<br />Nail set<br />Utility knife<br />4-foot builder's level<br />Straightedge (slightly narrower than the door opening)<br />Framing square<br />Wood shims<br />8d finish nails<br />2 ½-inch plated deck screws

Instructions

1. Begin by doing a preliminary check of the rough opening. The two wall studs at either side of the opening, called “trimmers,” should be plumb and parallel.<br /><br />Check the opening with a builder's level that both sides are plumb and the header is level, then measure horizontally between the two sides at the top, middle point and bottom to ensure the sides are parallel. Check the trimmers' faces with a square to ensure they are square to the adjacent wall surface.<br /><br />If trimmers are not plumb or square, use a pry bar to adjust the trimmer by moving it in or out at the top or bottom until plumb. Insert shims as needed to fill any gap between the trimmer and the wall stud behind it, then nail through trimmer and shims to secure in place.

2. Place a 4-foot level on a reliable straightedge that is 2 inches narrower than the opening. Rest both on the floor of the opening. If either side of the opening is lower than the other side, slide shims under the straightedge to adjust it until the level's bubble is centered. Always use two shims, one from either side, to keep the perpendicular surface level as well. Add shims at the center point of the opening to fill any gap that remains.<br /><br />Secure these shims in place with 8d finish nails. These will ensure the door sill will be supported as level.

3. Lift the door unit into the rough opening. Rest the sill of the unit on the floor or the shims installed in Step 2.

4. Temporarily wedge a wood block or shims under the doors where they meet in the middle. Position the block between the door bottoms and the sill as support during installation. The separation space, referred to as the “reveal,” between the doors should be equal and uniform. If the door’s center trim molding, called a “T-astragal,” is pre-installed, the reveal should be consistent and approximately 1/8 inch to 3/16 inch from top to bottom.

5. Use a pry bar to shift the door frame assembly in the wall opening to make the space between the door frame and wall framing equal on the both sides. Position the frame so that the interior surface of the jamb is flush with the adjacent interior wall surface and the sides are plumb.

6. Check the horizontal reveal between the top of the doors and the top jamb. It should be uniform and 1/8- to 3/16-inch-wide across the top of the doors. ??If necessary, adjust the reveal by pushing up the top jamb. Set this reveal and the door jamb by inserting shims above the top of the jamb, beginning at the center and driving an 8d nail through the jamb and shims into the header beam. With shims in place, check that top jamb is straight and level, and that the reveal is consistent.

7. The door frame assembly should now be plumb at both sides and level at the top and sill. Use a framing square to check the inside corners of the jamb unit, top and bottom.

8. Beginning at the top hinge on both sides of door frame, position shims centered behind the hinge location. Secure at each location with two horizontally placed 8d finish nails. As shims are placed, be sure to maintain a consistent reveal around perimeter of the doors on all sides. Also check that the jamb is not twisted and remains square to the adjacent wall framing.

9. Repeat Step 7 at the bottom hinges at both sides of the frame. Recheck the jamb with the builder's level to ensure it remains plumb as shims are installed.

10. Repeat Step 7 at the middle hinges at both sides of the frame.

11. Secure the top jamb by positioning shims at equal distances (approximately 16 inches apart) across top jamb and 3 to 4 inches from both of the top corners. Again, be sure to maintain a consistent reveal space across the top jamb over both doors.

12. Install any screws in the door sill designated by door manufacturer’s specifications. Shim as necessary to maintain level and equal distance to the bottom of the doors.

13. Remove the temporary support installed in Step 4 and swing the doors to the open position. Remove one of the hinge screws into the jamb from each of the top hinges. Replace these original screws with 2 ½-inch plated deck screws into the trimmer at each hinge. This will prevent sagging or binding of the doors over time. Be sure that the new deck screws are backed by shims and penetrate the trimmer by a minimum of 1½ inches.<br /><br />If the deck screws do not match the finish or head size of the original hinge screws, they can be inserted behind the hinge plate.

14. Use a small handsaw or utility knife to trim excess shims that protrude beyond door jamb on both sides of the opening.

15. Use a framing square to verify that the inside corners of the jamb assembly are square. Use a nail set to set all of the finish nails used to secure the jamb and shims.The doors and frame are now secure and ready for trim, hardware and final finish.

Tips & Warnings

• Prehung double door assemblies are heavy and cumbersome to maneuver. It is recommended that you enlist the assistance of a helper during the work.