Installing Bifold Doors

Synopsis: An experienced trim carpenter hangs a set of bifold doors on a closet, explaining why assembling jambs and casings together first makes the process faster and more accurate.

If you work as a trim carpenter long enough, sooner or later you’ll come to the realization that prefabricating components on a bench makes it easier to put them on the wall. I put this approach to work in all my trim-carpentry tasks. But in the case of installing bifold doors—the ubiquitous accordion-style panels that conceal many an American closet—the workbench is the floor in front of the closet. The job starts with the jambs.

Unlike prehung doors, which are hinged to their jambs when they leave the factory, bifold doors are typically shipped without the jambs. Instead, bifold doors are hinged to one another and packed in a cardboard box. The box also contains a bag full of hardware for hanging the doors. The doors illustrated here, for example, included the 2400 series Bi-Fold Door Hardware from Stanley. Detailed instructions for adjusting the hardware accompany the doors.

I typically purchase bifold doors from the same shop that supplies my passage doors. Along with the doors, I have the shop send along finger-jointed pine jamb kits for the doors (I prefer pine because nails driven into pine—unlike MDF, the other jamb-material option—don’t leave telltale dimples that need sanding).

Rough openings should be sized in a manner similar to those for passage doors by adding 2 in. to the nominal dimension of the doors. For example, a 5-ft. 0-in. bifold requires a 62-in.-wide rough opening. That leaves enough room for the jambs (two at 5/8 in. each) plus some wiggle room for plumbing the jambs. I frame my rough openings to be 82-1/2 in. high from the subfloor. That’s a standard 81-in. trimmer atop a 2x plate. Sharp-eyed carpenters will note that even though they are called 6-ft. 8-in. doors, bifold doors are really 6 ft. 7 in. tall. The missing inch allows room for the track at the top of the doors.

The jamb kits often include 1×1 moldings that are meant to conceal the edges of the doors around the sides and the door track. I think they’re ugly. These clunky 1x1s give a tacked-on look to the trim that isn’t in keeping with the look of the passage doors. So I leave out the 1x1s, preferring instead a detail that I learned from an ace finish carpenter back in the 70s. As shown in the article photos, I add a 1×2 to the head jamb, and then conceal most of it with the same trim that cases the passage doors. I don’t use any stops along the sides of the doors because the doors can easily be adjusted to maintain an even gap between their stiles and the jambs when the side jambs are aligned correctly. Bifold doors swing on pins instead of on the leaf hinges common to passage doors. The pins fit into predrilled holes in the top and bottom of the doors. With this system, most of the loads exerted by the doors are delivered to the pivot brackets at the bottoms of the jambs. So don’t worry about heavy structural nailing through the jambs to keep the doors from sagging. You’ll note in the photos that I put blocks under the pivot brackets to keep them from being buried by carpeting. If the floor is to be hardwood, leave out the blocks and install the doors after the hardwood is in place.

Hardware varies a bit from brand to brand, but the principles are the same. The door closest to the jamb is the pivot door. Its mate is the guide door. The pivot bracket at the bottom of the jamb is fixed, but the pin can be moved along its serrated slot to fine-tune the pivot door’s distance from the jamb. The pin at the top of the pivot door fits into a bracket in the door track that can be adjusted with a set screw. The pin in the guide door fits into a sliding, spring-loaded guide that snugs against the other pair of doors, holding them tightly together when closed.

1. Start by assembling the jamb. First, Britton spreads out the jamb parts in front of the closet. Then he uses a pneumatic stapler to anchor the side jamb to the head jamb.	2. A 1x strip hides the door track. Once the jambs are assembled, the author attaches a 1×2 to the inside of the head jamb. The door track tucks against the backside of this strip.

3. Next, nail the casings to the jamb stock. Leaving a 3⁄16-in. reveal around the inside edges of the jambs, Britton readies the jamb assembly by nailing on the casings.	4. Shims elevate the jambs. With a spirit level long enough to span the rough opening, the author assesses the floor for level and places shims accordingly next to the trimmer studs. The shims, which are at least 3⁄8 in. thick, lift the jambs enough to accommodate the carpet.

5. Lift the pretrimmed jamb into its opening. With the bottoms of the side jambs sitting on their shims to ensure a level head jamb, Britton slides the jamb assembly into the rough opening. Affixing it to the rough-opening frame starts from the top down.	6. Center the head jamb. Next, Britton slides the assembly from right to left, and marks the positions with a pencil. Splitting the difference centers the jamb. One nail through the casing into the header maintains alignment at this stage.

7. Plumb the side jamb. Britton uses the 6-ft. level to check the side jamb for plumb, moving the bottom of the jamb toward or away from the trimmer until the bubble is centered. Once he’s got it right, he affixes the casing to the trimmer with a nail near the bottom of the jamb.	8. Shim the jamb, and nail it home. Once the jamb has been plumbed, it can be permanently affixed to the trimmer. Britton uses a 15-ga. nailer, driving the fasteners through shims to keep the jamb from deflecting toward the framing as the nails slam home.

9. Now go to the other side. The bottom of the opposite jamb is located with a tape measure. The distance between the jambs at the top should be repeated here. Double-check for square by measuring the diagonals from casing corners to jamb bottoms.	10. The head casing gets nailed on last. Britton takes a slight bow out of the head casing by flattening it against the level as he nails the casing to the header.

11. Screw the track to the head jamb. The door track fits flush against the 1×2 nailed to the inside of the head jamb. If the screws reach the header, be sure to shim the jamb to keep it from deflecting.

12. Align jamb brackets with the door track. At the base of each side jamb, an L-shaped bracket supports a pivot pin mounted in the bottom of the pivot door. The serrations in the slot capture the star-shaped pivot pin at the bottom of the door, holding it at the desired distance from the jamb. The bracket sits atop a 3⁄8-in. thick plywood block, which keeps the bracket from being buried by the carpeting. A pencil mark on the side jamb notes the centerline of the door track above.

15. Install the doors from the top. Insert the top pivot pins into their slots, and push up to compress the springs. This makes room for the lower pivot to clear the jamb bracket as its pin is located in the serrated slot.

16. Ready for knobs. The door closest to the jamb in a pair of bifold doors is called the pivot door. Its mate is called a guide door. You’ll get the best leverage for opening and closing the doors by affixing the knobs to the pivot doors.	17. Aligners keep the guide doors flush with one another. Metal tabs called aligners are installed about 12 in. above the floor on the backside of the bifold doors. As the doors are brought together, the aligners engage one another to snap the doors closed.

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