07/05/2026
1. The Flexible Joint (Left Tree)
This side is engineered to dynamic movement. It supports the load of the beam while allowing the tree to sway and expand without tearing the treehouse apart.
The Support Bracket: Two pieces of $\frac{3}{4}\text{"}$ P.T. (Pressure-Treated) plywood are rigidly attached to the tree trunk using heavy-duty $\frac{1}{2}\text{"} \times 6\text{"}$ lag screws. This creates a solid "shelf" or corbel for the beams to rest on.
The Beams: The main load is carried by a pair of $2\times8$ P.T. beams. They rest on top of the plywood bracket but are not bolted to it.
Dynamic Movement:
"Allows for movement in all directions" and "Allow space for beams to twist": Because the beams just rest on the bracket, they can slide forward, backward, or twist slightly as the trees move independently.
$\frac{5}{8}\text{"}$ Nylon Rope: Instead of hardware, a heavy nylon rope is looped through the beam and around the tree. The notation specifies it "attaches beam loosely to tree for tree expansion." This keeps the beam from falling off its platform while granting it the freedom to shift.
Chaffing Protection: To prevent the moving wood beams from wearing down, $4\text{"}$ Galv. Steel Mending Plates are installed at the contact points to resist chaffing.
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2. The Fixed Joint (Right Tree)
This side acts as the anchor for the structural span.
Rigid Attachment: Unlike the loose, rope-tied side, the $2\times8$ P.T. beams on this tree are bolted directly into the trunk using heavy lag screws.
The Pivot Point: Because this side is completely fixed, it acts as a stationary pivot. When the wind blows, the right side stays put, and all the structural shifting and sliding safely happens on the left "Flexible Joint" side.
Configurability: The drawing notes that a "2nd beam [is] optional" depending on the weight requirements of the deck or structure being built.
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Summary of Materials Mentioned
Lumber: $2\times8$ Pressure-Treated (P.T.) Beams, $\frac{3}{4}\text{"}$ P.T. Plywood
Hardware: $\frac{1}{2}\text{"} \times 6\text{"}$ Lag Screws, $4\text{"}$ Galvanized Steel Mending Plates
Cordage: $\frac{5}{8}\text{"}$ Nylon Rope
