Install Concealed Joist Ties: Kerf, Rout, Dowel

The Problem

Exposed timber work — a pergola, a timber-frame porch, an architectural deck beam — looks wrong wearing a galvanized bucket hanger on its face. Concealed connection hardware solves the look, but it only works if the install is precise: the whole tie has to disappear inside the wood while still landing the joist exactly where the layout says.

The Technique

The sequence for a concealed joist tie (this install used Simpson Strong-Tie CJTs, sized here for a 5-1/2-inch beam with six dowels):

1. Cut the kerf. Saw a slot into the end of the joist for the tie's knife plate. A 16-inch beam saw is the right tool here — a thicker blade gives the plate a little wiggle room in the slot. Test-fit the tie in the kerf.
2. Rout the flange recess. Set the tie in place, mark its outline with a marker, and rout inside the line — a 1/2-inch plunge bit set to a 1/2-inch depth — so the hardware sits fully buried and hidden inside the member.
3. Lay out the dowels. Mark the dowel positions both directions (this size called for marks at 2-3/4 inches), and connect the lines so every hole lands centered on the plate's holes.
4. Drill from both sides. Run the 1/2-inch bit in from each face separately rather than punching through — cleaner holes, no blowout, and the two bores meet on the plate.
5. Assemble. Seat the tie, drive the dowels through plate and timber, and land the mating piece on the post: set it to the top, center it on the post's centerline, and the joist hangs on hardware nobody will ever see. Leave the specified clearance for the screws that lock it.