When a nerd designs a treehouse

When I was younger, my uncle came over to our house and helped my brother and I build a treehouse. We were fairly young, so basically he built us a treehouse. It was awesome until we nailed so many boards into the tree that it dies a painful death. Up until then it was the best things ever.

My kids are 5 and 2, and my 5-year-old asked me for a treehouse. This was based, incidentally, on an episode of Curious George that had been on. Still, thinking of how much I loved my treehouse, I was keen to give him one as well. It helps that I loved watching episodes of Treehouse Masters, and I wanted to put my spin on things. That's when my inner nerd kicked in.

We have a tree in our yard. Well, not really our yard, but the dog's yard. It's a large sycamore, beautiful shade tree, and has three large trunks shooting off the central one.

Here's where things got hung up in my mind:
A) The tree is in the dog's part of the yard, which makes it harder to access and lends the whole thing to smell like dog doo.
B) The tree is large and strong, but drops good-size branches on a fairly regular basis. Not ideal.
C) Trees have a limited and often unpredictable lifespan.

I wanted to keep things inside our nice fenced-in yard, so I came up with a treeless treehouse. Usually, they look like this.

Being me, this simply wouldn't do. A shed on stilts. Even with a slide, this is lame.

I decided on a three-sided structure. This was partially because of our three-legged tree, but also because I like the idea of a structure that wouldn't wobble. A triangle is also easier to construct because it doesn't need to be squared up. Triangles are 2-dimensionally rigid, which was also nice. I drew partially off of a neat party trick I saw involving three butter knives like so:

One supports the next and so on, until they all support each other, like magic. I then thought, "why not make it a three-sided pyramid?" The shape is technically a tetrahedron. It's a three-dimensionally rigid structure, resistant to deformation. The wide stance makes the structure very stable, which is nice in the winds around my house. I picked out a good spot in our yard (approved by my wife), and got the wood on order.

I would use three poles, 8" x 20' long for the main structure, and three smaller poles, 8" x 14' for the sides. I dug shallow holes for the feet, since the holes would not be the source of the structure's strength. One of the key reasons I opted out of the typical design (sinking poles deep in the ground and building off those) is that I didn't want the structure to depend on the quality of the holes. The tetrahedral shape would hold its shape even on a sheet of glass, theoretically.

Long story short, I have the skeleton of a treehouse, arranged tetrahedrally with the three poles coming together in a helical pattern at the apex.

I used 3/4" bolts to hold the poles together (three bolts are being use, though only two are needed to hold things in place), and I added steel bands to keep the poles from trying to split (both good suggestions courtesy of my father). I'm going to use this base structure to build all manner of awesomeness, which should be able to grow with my children for the rest of their childhood.

So there you have it. Just over 19' between the feet on the ground. About 14' from ground to apex. Bound to a triangular shape by the horizontal poles which are 6' off the ground at their lowest point. We'll be building a 6-sided hexagonal platform on top of the horizontal poles and enclosing a 6-sided room in the center of the pyramid. Final product should be large enough for sleepovers and whatever else we come up with.

TL;DR - Look, I built a giant teepee!

Dave