How to Install Door Jambs and Casing for a Bi-Fold Door

This project shows how to install door jambs and casing for a bi-fold door in this update of How To Build a Basement Closet. This series is continued from the Plywood Cap & Outside Corner Moulding Installation.

Bi-Fold Doors, Door Jambs and Door Casing

The materials for finishing the basement closet door are:

Basement Closet: Bi-Fold Doors, Door Jambs and Door Casing

Basement Closet: Bi-Fold Doors, Door Jambs and Door Casing

Details of the Masonite 24 in. x 80 in. bi-fold door. I chose this door because it’s prefinished and doesn’t need painting if you want a white door.

Masonite Full Louver Prefinished White Plantation Closet Door Bi-Fold 24 in. x 80 in.

Masonite Full Louver Prefinished White Plantation Closet Door Bi-Fold 24 in. x 80 in.

The ready-to-install 4916PFJ 11/16 in. by 4-11/16 in door jamb:

4916PFJ 11/16 in. by 4-11/16 in Door Jamb

4916PFJ 11/16 in. by 4-11/16 in Door Jamb

Close-up of the pre-cut rabbet in the door side jamb so the head jamb fits flush.

Pre-Cut Door Jamb Rabbet for the Head Jamb, Model 4916PFJ

Pre-Cut Door Jamb Rabbet for the Head Jamb, Model 4916PFJ

Closet Door Jamb Installation

A door rough opening is typically built 2.5 inches wider and 2 inches taller than the finished door to allow for irregularities in the 2×4 framing and provide space for the two 11/16 inch thick door jambs. The door jambs are then “trued up” during installation with shims placed between the 2×4 rough opening and door jamb.

As explained in How to Build a Basement Closet – Part 3, I worked carefully using precise measurements and very straight 2×4 lumber to build the rough opening square, plumb, 81-11/16 in. high and 49-5/8 in. wide. After installing the two 11/16 inch thick side jambs (equals 1-3/8 inches total thickness), the finished door opening will be 48 inches (48 = 49-5/8 minus 1-3/8). The result is my door jambs do not require shims. I personally don’t like shimming door jambs because a large part of the jamb will be unsupported. The bi-fold door scale drawing should clarify the framing details and dimensions:

Bi-Fold Door Rough Opening Framing Diagram

Bi-Fold Door Rough Opening Framing Diagram

Measure and Fit the Door Jamb Header

The two side jambs are temporarily set in place, checked for plumb and fastened with a single 1-1/2 inch brad nail. Then, the length of the header jamb is measured from rabbet-to-rabbet.

Closet Door Side Jambs

Closet Door Side Jambs

The header jamb is cut from a length of side jamb stock, using the section without the rabbet because the header does not need the rabbet groove.

Sawing the Door Header Jamb

Sawing the Door Header Jamb

The header jamb fit is checked by slipping it in the side jamb rabbets:

Door Jamb Installation: Fitting the Header Jamb

Door Jamb Installation: Fitting the Header Jamb

The header jamb is slipped off the side jambs, then the side jambs are pulled free of the rough opening. The single brad nail that temporarily held the side jambs in place pulls out easily.

The header jamb is fitted and squared with the side jamb, then the side jamb is fastened to the header with a couple of 1-1/2 inch brad nails. Be careful to drive the brad nails straight so it doesn’t exit the surface of the header jamb. The other side jamb is  the same method.

Door Jamb Assembly: Side and Head Jambs

Door Jamb Assembly: Side and Head Jambs

The assembled door jambs are stood up and ready to be set in the rough opening.

Closet Door Jamb Installation

Closet Door Jamb Installation

The door jambs are set even with the closet drywall, checked for square and nailed to the 2×4 framing with 2 inch long six-penny (“6d”) finishing nails.

Check Door Jambs for Square

Check Door Jambs for Square

The finish nails are set in side-by-side pairs spaced 1 inch horizontally and ~16 inches vertically along the jambs. Nail both the side- and header jambs with 6d nails.

Door Jamb Installation: 6d Finish Nails

Door Jamb Installation: 6d Finish Nails

The nails are countersunk (i.e. the nail head is driven ~1/8 inch below the door jamb surface) with a nail punch. (If you don’t have a nail punch, a 16d nail can be used to countersink the finish nails.) The nail heads will be filled with wood putty and sanded flush with the wood surface before painting.

Closet Door Casing Installation

The 2-1/4 inch wide door casing was chosen because it matches the door casing in my home. The inside finished height of the door is measured and 1/4 inch is added for the casing setback (see the casing detail in the 3rd photo below). Then the 45 degree miter cut made on the Dewalt Compound Miter saw. Measure and install the side casings first, then the door header casing.

Closet Door Casing Miter Cut

Closet Door Casing Miter Cut

The door casing is fastened with 2 inch brad nails. The brad nail gun does a great job without jarring the work piece and automatically countersinks the brad nails.

Building a Basement Closet: Door Casing

Building a Basement Closet: Door Casing

Closeup of the door jamb and door casing installation. Notice how the door casing is set back about 1/4 inch from the face of the door jamb for a bit fancier trim detail.

Door Jamb and Door Casing Installation Details

Door Jamb and Door Casing Installation Details

Door casing installation details at the concrete floor:

Door Casing Installation Details

Door Casing Installation Details

The completed door jamb and casing installation after filling and sanding the brad & finish nail heads with wood putty. I’ve also painted the closet walls. The closet door jambs, casing and outside corner moulding will be painted next.

Door Jamb and Door Casing Installation

Door Jamb and Door Casing Installation

The bi-fold doors, baseboard and clothes racks will be installed in the next project update.

Take care,

Bob Jackson

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8 Responses to How to Install Door Jambs and Casing for a Bi-Fold Door

  1. bob September 11, 2014 at 9:49 am #

    good job, thanks.
    But you didn’t leave room for flooring, so you will have to cut your jambs on the bottom to slip your flooring underneath.

    • Bob Jackson September 11, 2014 at 7:23 pm #

      I didn’t leave a gap below the door jambs for carpet/tile/wood flooring because I finished the concrete floor with SkimStone. It’s so much cleaner than carpet, less expensive the wood flooring and a better choice IMHO for a basement slab floor. Because SkimStone is a portland cement based product it’s waterproof which is nice for a basement.

      See How to Finish a Basement Bedroom for the complete project.

      Thanks,
      Bob

  2. James February 8, 2015 at 10:51 am #

    “build the rough opening square, plumb, 81-11/16 in. high and 46-5/8 in. wide. After installing the two 11/16 inch thick side jambs (equals 1-3/8 inches total thickness), the finished door opening will be 48 inches (48 = 46-5/8 minus 1-3/8)”

    Shouldn’t this be:

    build the rough opening square, plumb, 81-11/16 in. high and 49-3/8 in. wide. After installing the two 11/16 inch thick side jambs (equals 1-3/8 inches total thickness), the finished door opening will be 48 inches (48 = 49-3/8 minus 1-3/8)?

    • Bob Jackson February 9, 2015 at 8:50 pm #

      Hi James,
      Thanks for catching the error in the my writeup! The math is supposed to be as you stated. I’ve made the correction in the project and added a scale drawing, which is included here for clarity. As the saying goes, “A picture is worth a thousand words”.

      Bi-Fold Door Rough Opening Framing Diagram

  3. Morasco Remodeling March 3, 2015 at 7:23 pm #

    Super helpful tutorial! After doing countless closet bifold openings finished in drywall, I finally had a customer request wood and trim finishing in the opening. The only tip I’d like to offer is regarding the casing installation. For years I cut and installed the side legs first and then the top piece last like you recommend. Then one day I learned a tip from another pro. Measure your opening at the top left to right, add 1/2″ to that measurement and miter cut your top piece first. Level and nail it in with 1/4″ reveal. Then you simply measure your side legs to the floor, cut and install. This method saves tons of time and frustration and allows you to keep your miter joints nice and tight. Just nail the top of each side leg first insuring a tight miter, and work your way down keeping a consistent reveal. The side legs will flex some whereas the top piece cannot be flexed because there is a miter on each end. I know it sounds like it won’t make a difference, but just try it once and you’ll never go back to the old way.

  4. Matt January 17, 2016 at 8:22 pm #

    Head casing 1st. Measure inside. Add 1/2″ for reveal. Then cut your 45 on the side casings. Hold them upside down in front of the jamb and mark your square cut where it intersects the head casing at the top. This is the way you cut trim for any door opening quickly and precisely.

  5. Phyllis Jones March 4, 2016 at 11:10 am #

    I have an open alcove ( has 3 walls and angled ceiling). I would like to enclose it with a set of beautiful solid wood louvered doors. How do I build a frame above the area to support the doors? My doors will fit the opening without installing the side door jams. I could plane the doors to allow extra room for them, if required, but the walls are quite strong.

    • Bob Jackson March 5, 2016 at 12:07 pm #

      Hi Phyllis,
      You’ll need to determine the location and direction of the ceiling joists to know where to fasten a 2×6 top plate with long wood screws. Because the ceiling is angled (sloped) the 2×6 will have be bevel ripped on a table saw so the front and back edges are flush (vertical) with the framing to install the new drywall per this diagram:
      Angled Ceiling Bi-Fold Door Framing

      Note dotted blue lines indicating where the 2×6 needs to be bevel ripped. The drawing is true to scale for the 2×6, 2×4 and 1/2 inch thick drywall. Note that a 2×4 top plate would be too narrow therefore a 2×6 is needed for a perfect fit after the angled (beveled) rip cuts.

      The door header cripple studs will have to be notched to fit the angle of the top plate.

      Thanks,
      Bob

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