How to Shim a Door Frame

A properly squared door does not rub against the frame while being opened or closed.

New interior doors give your home an updated appearance. Many homeowners choose to save money and install the new doors themselves. While this is not a difficult task, it does require attention to detail. If the new door is not square in the door opening, the door's corners will rub, making it difficult to open and close. Shims are thin wooden strips used between the door frame and the rough opening to hold the frame square.

Things You'll Need

• 4-foot level
• Drill
• Phillips-head drill bit
• Drywall screws
• Pneumatic nailer
• Finishing nails, 2 1/2 inches

Instructions

1. Center the new door frame into the opening. If the frame comes with a prehung door, close the door. Hold a 4-foot level against the frame's hinge side.

2. Slide wooden shims between the door frame and the rough opening in three places; behind the top, middle and bottom hinges. Shims are wedge shaped, so the further you push them in, the further out they push the frame. Adjust the shims until the frame's hinge side is firmly positioned straight up and down. Use two shims behind each hinge, if necessary, to achieve the perfect spacing.

3. Use a drill and a Phillips-head drill bit to insert drywall screws through the frame, shims, and into the rough opening. Screws are used on this side instead of finishing nails because they hold the frame in place better throughout years of use.

4. Lift or lower the door frame's knob side so that the gap between the frame's top board and the rough opening is equal all the way across. Place a level against the frame's knob-side board.

5. Insert shims at approximately the same heights as the previously installed shims. Once the frame's knob-side board is straight up and down, use a pneumatic nailer and 2 1/2-inch finishing nails to secure the frame in place. Insert the nails through the frame, shims and rough opening.

Tips & Warnings

• Hide the screws used on the frame's hinge side by removing the screws holding the hinge leaf in place. Insert drywall screws underneath the portion of the frame the hinge leaf covers. Put the hinge leaf back on the frame and secure it in place.

References

• Masonite: Installation Instructions for Interior Prehung Doors
• Midwest Manufacturing: Prehung Interior Door Installation
• Ask the Builder; Pre Hung Interior Doors; Tim Carter