Friday, May 14, 2021

Phase IV Treehouse Support Structure Complete


Just as the foundation is one of the most important parts of building a house so is the supporting structure for a Treehouse. Fortunately this Oak tree is dead so I did not have to keep the health of a living tree in mind when I attached the supporting beams to the tree. 

Beam material would be 2 by 8 rough sawn Oak plank. Since the pieces I had were not 10 feet long I needed to lap and screw two pieces together. This would not be a problem as each beam was going to be supported in two places about 2 feet from their center point by the 1 foot diameter tree limbs in the crotch of the tree.

Doing all this from 30 feet in the air was not going to be for the faint of heart. But a good learning experience and some "serious fun".

I choose 2" square box tubing and 3/16 by 2" flat stock to fabricate the braces that would help carry the load of the 1675 pound Treehouse. You can see the braces on the model. A change in the elevator design shortened the length of the beam shown on the model by about 3 feet so it will not be sticking out that far to the left.

OK, the first two main beams, shown running from left to right were notched into the tree. The notch gave the beam a positive support point that would carry the load and would only need screws to hold them in place. Rubber roof membrane was placed over the exposed end grain of each notch to keep out any water. Although I don't see this as being much of a problem as the finished Treehouse will be covering this area.

You can see the ladder has been extended by clamping a section of aluminum ladder to my 24 foot fiberglass extension ladder. This got me right to the crotch of the tree and eliminated the need to climb the 2x4 steps screwed to the tree. It also brought visions of a poster I saw in a local business showing various jury rigged things like this and was titled, "Why Women Live Longer Than Men!"

With the first two main beams in place a center mast was installed that provided two attachment points. One for the rope and pulley to bring up tools and materials until the elevator is in operation and a second point for a safety harness line. This point was offset and can swivel so I can work around the perimeter of the Treehouse and not get wrapped up like a dog on a chain.

You can also see the first of the four diagonal braces hanging from a second level support beam.

Things are moving right along now. With the first set of diagonal braces hanging down and ready to be attached to the tree trunk. 

Strength, load path and tying everything together is always my main concern. I know the tree trunk could stand it because it survived the wind storm that tore away the massive tree top several years ago. I needed to make sure those forces, should they occur again not knock out the Treehouse and send it crashing to the ground. Or worse land on Cabin #6! To accomplish this each of the second level beams, crossing at right angles to the main beams were tied together with ready bolts and plates like this.

So all this might look easy but I can tell you a project like this keeps you on your feet and there are plenty of things to consider if the outcome you want is to be square and level like this. In a tree. Thirty feet in the air no less.

Oh wow, went as planned, so far so good.

Imagine the view in the fall and winter. All 360 degrees of it.

Next up, Phase V Disassembly of the Treehouse and Placing the Floor.

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