Steps
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How to Build a Tree Fort
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Screw in the Hardware
Step Three
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How to Build a Tree Fort
Screw in the Hardware
Using a 1 1/8-inch auger bit, drill 2 inches into the middle of the first hole; make sure it’s level. Then use a 1-inch auger bit to drill another hole 4 1/2 inches deep to accept the threads of the tree bolt. Slip the pipe bracket that will support the framing onto the tree bolt, cap it with a hex nut, as shown, and twist the threaded end into the hole with a 1 7/8-inch socket wrench (or a pipe wrench). Repeat the process on the opposite side.
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Form the Bird’s Mouth
Step Seven
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How to Build a Tree Fort
Form the Bird’s Mouth
Start by making a mark on the board face 2 1⁄4 inches up from the bottom edge of the 4x6. Rest the shoulder of the rafter square against the bottom edge with the 45° angle facing the board end. Draw a 45° line from the mark to the bottom edge. Flip the square over with its shoulder against the opposite edge and the angle facing the end. From the mark, make a second line along the angle to the top edge, creating an angled L, called a bird’s mouth, on the face of the timber. Start the cut along the lines with a circular saw, then finish with a reciprocating saw, as shown. Now measure from the corner of the L and cut the timber to length.
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Connect Brace to Header
Step Ten
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How to Build a Tree Fort
Connect Brace to Header
Toenail 2x8 joists 16 inches on center to the carrying beams with ring-shank nails to create an 8-by-10-foot framework. Use hurricane ties to reinforce the joist–beam connections. Lift the header about an inch with a 4x6 and a bottle jack—you’ll remove it to put tension on the brace once it’s installed. Hold the brace in place with the bird’s mouth biting the header. Drive a pair of 6-inch structural screws through the outside of the header and into the 4x6, as shown.
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Bolt Hardware to the Tree
Step Eleven
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How to Build a Tree Fort
Bolt Hardware to the Tree
Hold the end of the knee-brace bracket to the tree. Using the metal tube as a guide, drill an 8-inch-deep hole into the tree with a 1 1⁄4-inch auger bit. Thread a 15-inch galvanized lag bolt into place and tighten it with a socket wrench. Leave a few inches between the bracket and the bolt head to accommodate tree growth. Now lower the jack and repeat the process on the other side of the tree.
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Scribe the Short Pieces
Step Thirteen
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How to Build a Tree Fort
Scribe the Short Pieces
Now work in the other direction, installing the boards interrupted by the tree. Scribe the ends to follow the contour of the bark, as shown. Cut the marks with a jigsaw, and attach the boards, again leaving 3 inches for growth. Install all the interrupted pieces, then continue laying full-length boards, stopping a foot shy of the joist ends. With the decking in place, trim the ends of the boards with the jigsaw, creating a natural edge.
Tip: To accurately scribe the boards that run into the tree trunk, hold the compass so its legs are parallel with the joint in the boards.