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Prehung Interior Double Doors Print
Overall Skill Level: Expert

Installation instructions for prehung interior double doors.
Steps
  1. Install the Door
    1. Check rough opening dimensions
    2. Remove bottom board from the door
    3. Place door into rough opening
    4. Shim under the center of the door
    5. Remove bracing from the interior side
    6. Shim the hinges of the inactive door
    7. Pre-drill the top hinge shim and secure the door with a finishing nail
    8. Verify inactive door jamb is square and plumb
    9. Pre-drill and use finishing nails on the other hinges of the inactive door
    10. Secure hinge side door
    11. Verify margins
    12. Shim the top of the door
    13. Fasten the head jamb
    14. Use a second set of finishing nails to help secure the frame
    15. Replace the center hinge screws with a 2 1/2" screw
    16. Skip this step if your unit does not have an astragal.
    17. Finish the door unit.
Tools
  • 6' Level
  • Square
  • Hammer
  • Drill
  • Tape Measure
Materials
  • Interior Door
  • Shims
  • 2 1/2" Finishing Nails
  • 2 1/2" Screws
  • Stain, Paint, or Clear Coat
Install the Door
Skill Level: Expert
  1. Check rough opening dimensions
    Check your rough opening dimensions. The rough opening height should equal the door height plus 2 ½". Standard door height is 80". The rough opening width should equal the door width plus 2" for a door without an astragal and plus 2 ½" for a door with an astragal (Figure 1).
  2. Remove bottom board from the door
    Remove the bottom board from the door unit. Cut the cardboard on the bottom corners of the unit (Figure 2).
  3. Place door into rough opening
    Set the bottom of the door unit in the rough opening and tip the top of unit into place.
    WARNING: Door units are heavy! Use an adequate number of people to set unit to prevent injuries and damage to door.
  4. Shim under the center of the door
    Shim under the center of the door unit to support the doors and prevent them from sagging (Figure 3).
  5. Remove bracing from the interior side
    Remove the bracing from the interior side of door using a hammer. Place a wood block on the surface of the jamb to avoid damaging the wood of the door unit (Figure 4).
  6. Shim the hinges of the inactive door
    Place shims between the door unit and wall by each of the three hinges on the inactive door. Note: The inactive door has the astragal attached.
  7. Pre-drill the top hinge shim and secure the door with a finishing nail
    Make sure the door unit is flush with the edge of the sheet rock. Pre-drill a hole through the door stop in the location of the top hinge shim. Use one 2 ½" finishing nail to hold the door in place (Figure 7).
  8. Verify inactive door jamb is square and plumb
    Place a 6' level along the jamb that was shimmed in step 6 to make sure the jamb is square. Adjust the middle and lower shims until the bubble on the level is exactly in the center (Figure 5). After the jamb is square, check for plumb on the jamb. Rotate the level so it is sitting flat along the jamb (Figure 6).
  9. Pre-drill and use finishing nails on the other hinges of the inactive door
    Once the inactive door jamb is square and plumb, pre-drill a hole through the stop in the location on the middle and bottom hinges. Use 2 ½" finishing nails to tack the frame in place (Figure 7).
  10. Secure hinge side door
    Once the inactive door is shimmed and nailed into place, repeat the process on the active door side. First begin by shimming the three active-side hinges the same as step #6. Check for plumb and square as described in step #8 and then pre-drill and nail the jamb into place through the jamb stop using the 2 ½" finishing nails in the location of the three hinge shims as in steps #7 and #9.
  11. Verify margins
    Check for equal margins on the door unit. With both doors closed, where the doors meet in the center, there should be an equal space from top to bottom. If the margin is not even or if the doors hit, the door unit may be slightly out of square or shimmed incorrectly. To correct this problem, recheck the square on the doors and make adjustments to the shims. (Remember, even if the bubble is between the lines on the level, it does not mean that the doors are square. The bubble needs to be equally spaced between the two lines.)
  12. Shim the top of the door
    Place shims in three locations across the top of the door unit, between the head jamb and wall - one shim in the center of the door unit, the other two centered over each door (Figure 8). Adjust the shims until there is an even margin between the door and the frame across the top of both doors.
  13. Fasten the head jamb
    Pre-drill through the door stop in the location of each of the three shims (Figure 9). Nail the head into place using 2 ½" finishing nails.
  14. Use a second set of finishing nails to help secure the frame
    Once the initial finishing nails are in place on both of the active and inactive jambs, a second set of nails will be needed to help secure the frame. To do this, first begin by opening the active door and placing a second nail through the narrower side of the jamb for each of the shim locations (Figure 10). This process should then be repeated on the inactive door side. When all the finishing nails have been installed, use a nail set to sink the heads of the finishing nails.
  15. Replace the center hinge screws with a 2 1/2" screw
    Once the second set of nails is in place, the center hinge screw should be removed from the top hinge on the frame (not the door side of the hinge) and replaced with a 2 ½" screw. Replace this center screw on all six hinges (Figure 11).
  16. Skip this step if your unit does not have an astragal.
    With the inactive door open, raise the head pin about ¼". Using a black permanent marker, color the top of the head pin. While the marker is still wet, lower the head pin and close the door tightly. Raise the pin until it touches the head jamb. This should leave a black circle on the head jamb. Use a punch to mark the center of the head pin mark and then drill a 5/16" hole. Now place the strike plate so that the center hole in the plate is directly over the hole drilled. Screw the strike plate into place and use a utility knife to score around the edge of the plate. Remove the plate and use a small wood chisel to remove any undesired wood. Once the strike plate has been properly mortised, screw the strike plate back into place. Repeat this process for the foot pin.
  17. Finish the door unit.
    A. Before finishing, a light final sanding is recommended over all surfaces of the door. Remove sanding residue before applying sealer or finish.
    B. Stain, paint, or clear coat following the finishing manufacturer's recommendations.
    C. To prevent delamination and warpage, all six sides of the door must be sealed. Doors may not be cut or altered, or warranty is void.
Products, materials, techniques, tools, building codes and local regulations are subject to change; therefore, Midwest Manufacturing assumes no liability for omissions, errors or the outcome of any project. The reader must always exercise reasonable caution, follow current codes and regulations that may apply, and is urged to consult with a licensed professional before beginning any project.