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King Post, Truss Assembly King Post, Truss Assembly From "Trade School" episode DTRS-113

Figure A

In this segment, we follow Gideon as he crafts a king post, one of the more complex pieces in a timber frame. The king post is the central vertical timber in a roof truss. A roof truss is triangular network of timbers that, spaced along the length of the house, form a rigid structure to support the roof. The king post serves as the main piece --- all members of each roof truss tie into it (figure A).

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Basic Tools:

Tape measure
Speed square
Combination square
Circular saw
Disc sander
Chainsaw mortiser
Framing chisels
Belt sander
Chainsaw
16" Beam saw
Band saw
Ratchet straps
Reciprocating saw
Hole Hog

• Gideon first cuts off a suitable piece of timber from the stock using a chainsaw (figure B).

• With Ezra's guidance, Gideon goes over the plans for this particular king post and begins marking the dimensions on the timber (figure C). Two angled edges come together to form the tip and match the slope of the roof.

Figure B

Figure C

• Gideon first marks the tip in the center of the post and uses a speed square to mark the angles from this point (figure D).

• The tenons of two rafters later meet together inside the top of the post, so Gideon marks a 2-inch mortise that bisects the peak. When complete, this mortise causes the peak to resemble a two-pronged fork. Gideon also lays out angled shoulders for the rafters just below the head (figure E). At the bottom of the post, he measures and marks a 2-inch tenon, which will fit into a beam called a collar tie.

Figure D

Figure E

• With the layout complete, Gideon begins cutting the post to size. Using a 16" beam saw, he cuts the two marked angles at the top of the post (figure F). He flips the post over and finishes these cuts with a circular saw (figure G).

Figure F

Figure G

• With the beam saw, he makes partial cuts to the tenon on the bottom of the post (figure H). Then, he sets the circular saw at a 45-degree angle and makes partial cuts for the post shoulders (figure I). Gideon later finishes these cuts on the band saw.

Figure H

Figure I

Using the chainsaw mortiser, he digs a square hole through the head of the post (figure J). Later, this hole will enable Gideon to rotate the post around a band saw blade (figure K).

Figure J

Figure K

• With help from Ezra, Gideon transports the king post to the band saw. They start by cutting the mortise in the post head. With a steady hand, they cut into the middle portion of the wood, until reaching the square hole created by the chainsaw mortiser. Then, they carefully maneuver the post around the saw blade and make an exit cut to remove the center piece of wood. (figure L).Gideon continues by finishing the cuts already started on the shoulders and tenon (figure M).

Figure L

Figure M

• Having completed the cuts, Gideon refines the shape of the king post using a disc grinder with 30 to 40-grit paper. He double-checks the lines with a straight edge (figure N), and cleans up the forked crown with a chisel (figure O).

Figure N

Figure O

Figure P

• To complete the king post, Gideon sands all the surfaces smooth with the hand-held belt sander (figure P).

In the next segment, Gideon assembles and test-fits a roof truss.