In a previous article, “Installing a Pocket Door” (May/23), I described the installation of one of Johnson Hardware’s commercial-grade pocket-door kits, which are assembled on site. For a recent project, I chose to use a prefabricated pocket-door assembly—also from Johnson Hardware—for a couple of reasons, which I’ll describe in a bit more detail below. But when it came time to pick up the door and the pocket-door assembly, it turned out the lumberyard didn’t stock the assembly in a size that matched the door.
Solid-core door. I was replacing a standard hinged door with a 2-foot 2-inch solid-core birch door, the maximum size that would fit in the tight space available for it. Solid-core doors are heavy, which is why I like to use them with pocket-door hardware; the weight helps them to roll more smoothly on their track.
Johnson Hardware’s 2710/2711 series of prefabricated pocket-door frames come in sizes to fit 24-, 28-, 30-, 32-, and 36-inch-wide doors. Even if the company offered a size to fit a 26-inch door, I would have had to order it and wait to have it delivered. But the lumberyard did have a 30-inch prefab unit in stock, which I could cut down to fit to keep the job moving, so I loaded it into my truck and brought it to the job. Trimming these units is relatively straightforward and, in this article, I’ll describe how I did it.
Trim to fit. Compared with Johnson’s pocket-door kits, which come knocked down into easily transported boxes, the prefab units are bulky. The 30-inch unit I bought actually measured 61 3/4 inches wide by 84 1/2 inches tall and, while it wasn’t particularly heavy, maneuvering it into the cramped area where it would be installed was tricky. But compared with the kits, the prefab units feel a lot sturdier, with horizontal blocking and metal split jambs that are reinforced with plywood rippings, which make the jambs more rigid and less likely to bow. And, when I don’t have to modify the frame to make it smaller, installation of a prefab unit is a lot quicker than assembling a kit on site.
To fit the unit in the rough opening, I needed to trim the total width by 8 inches, so that it would measure 53 3/4 inches wide. After unscrewing the aluminum track from the header, I ripped a 1x4 to the same dimension as the existing jamb on the framed pocket, on the side of the unit that gets buried in the wall. Next, I measured and marked the new jamb location on the framed pocket so that its width would be 4 inches less, or sized for a 26-inch rather than 30-inch door. Then I slipped the new jamb into the frame, leaving the existing jamb intact for the time being.
With the top of the new jamb aligned with my layout mark, I drove a GRK structural screw through the header assembly and into the jamb. I continued to fasten the jamb to the horizontal blocking with more screws, checking with a tape measure as I went that the old and new jambs were parallel to each other.
Once the new jamb was secured to the pocket-door frame, I used a track saw to trim the unit to the new width, aligning the track with the edge of the jamb. After I’d cut the box frame on one side, I flipped the unit over and completed the cut on the other side, separating the old jamb and short horizontal blocking offcuts from the original unit.
Next, I trimmed the aluminum track to length using a cordless DeWalt 4 1/2‑inch trim saw equipped with a regular carbide-tooth blade. Before refastening the track to the header, I needed to drill a new fastener hole in the track, to replace the one that was removed when I shortened the track. I also had to remove the rubber end bumper from the old jamb and remount it in the corresponding position on the new jamb. To complete the resizing operation, I also trimmed 4 inches from the end of the header.
Installation. Once I had managed to maneuver the unit into the rough opening, it took only a few minutes to install. First, I screwed the header assembly to the rough-opening header, using shims to make sure the track was perfectly straight and level. Then I made sure the box frame was plumb and perfectly square to the header before screwing through the jamb into the wall framing, using shims as necessary to keep the jamb straight.
Before mounting the hanger hardware on the door, I primed and painted all four edges. Then I hung the door from the rollers, using the supplied offset wrench to fine-tune the door so that it was perfectly parallel with the strike jamb.
When the door opening needs to be trimmed, the manufacturer recommends using screws on the hanger lock side of the split header trim, so that the trim can easily be removed at a future date if necessary. But I don’t like the look of screw heads on trim work, even when they’re dressed up with decorative washers. Instead, I used an 18-gauge brad nailer to fasten the trim in place. A pocket door doesn’t need to be removed very often and, if it does, it’s easy enough to pry off trim that has been nailed in place with 18-gauge brads.
