How to Build a Square Frame for a Bi-Fold Door

Bi-fold doors are common on utility, wardrobe and storage closets. Like bypass doors, which are also commonly used on closets, bi-fold doors operate by sliding along a track installed along the door's horizontal jamb. While open bypass doors reveal only half of a closet’s interior, bi-fold doors have hinged panels that fold flat when fully opened, allowing full access to the space they enclose. To properly install bi-fold doors, it’s essential to construct a square door frame so there's an equal margin of space between the edge of each door panel and the side jambs.

Drywall scraping tool
4-foot level
Jamb stock, cut to size
Wood glue
6d finishing nails
Framing square
Wood shims
8d finishing nails
Utility knife

Instructions

- 1
  Use a scraping tool to scrape away any excess drywall around the door opening so that the drywall and the doorframe are flush.
- 2
  Check the wood framing of the door with a 4-foot level to make sure it’s plumb. You will have some amount of play between the wood framing and the doorjamb for adjustments.
- 3
  Line the top edge of one of the side jambs with wood glue. Press it against the bottom of the top jamb, so that the outside edge of the top jamb is flush with the outside surface of the side jamb. Secure the joint with 6d finishing nails.
- 4
  Glue the remaining side jamb to the opposite end of the head jamb in the same manner and secure the joint with 6d finishing nails. Use a framing square to make sure each corner forms a 90-degree angle.
- 5
  Set the jamb in the door’s opening. Place wood shims between the jamb and the frame at the top, middle and bottom of the jamb to center it in the frame. Below each shim, tack 8d finishing nails through the jamb into the frame.
- 6
  Use your level to plumb each side jamb from top to bottom, adding shims as necessary to make the frame square.
- 7
  Ensure each side jamb is fully plumb by double-checking it with your level from top to bottom. Adjust the shims as necessary, then set all the nails to hold the jambs securely.
- 8
  Cut off the protruding portions of each shim with a utility knife before installing the bi-fold door. The remaining shims and most of the jamb will be obscured once you install the trim.

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