Building the Treehouse

Earlier this year, I asked Big Red and Little Red which one of three things we should build first: (a) a treehouse, (b) bike trails or (c) a zip line. The feedback was unanimous, and we began researching the kind of treehouse we would build this summer.

Treehouses can get pretty elaborate. A quick Google search on the subject reveals projects by individuals easily running $10,000 and up, outfitted with electricity, appliances, carpet, windows and more. Don't get me wrong, I admire the vision that these individuals have, and given unlimited time, money and resources, I might attempt such a structure. But times being what they are, and the myriad projects around the house, I looked for a design that was relatively simple, but offered a unique and authentic look and feel.

I found a goldmine of information in the books of David Stiles, a treehouse expert whose designs include 1, 2, 3 and 4-tree designs. I was intrigued by the 2-tree version, which looks like a pup tent balanced on two beams. See photo at left, from David Stiles' book.

The location I've chosen is about 50 yards behind the house - far enough to be removed from the house and not visible in summer, but not so far that essentials aren't accessible. Two oak trees were chosen as supports, each about 12" in diameter, very straight, and more than 70' tall. They stand about 11 feet apart from one another, which will make our finished platform size about 6' wide and 10.5' long.

Overall, the build will happen in three phases: (a) The main supports or joists, (b) The platform and (c) The Enclosure. I've just completed the main supports, and included a photo below. The two tricky parts of this build were sistering the 2x8s (bolting them together to improve their strength), and creating the flexible slot connections as suggested by David Stiles.

Why flexible slots? Simple really: Wind blow, trees bend. Only if identical wind gusts are blowing on identical trees will the trees (and the treehouse joists) move in unison. Because the trees bend differently, at least one joist connection needs to be flexible and accommodate varying amounts of sway. David Stiles provided different options for flexible slots, but the one that made the most sense for me was the grooves that would allow the four 1/2" lag screws (two on each joist) to move horizontally while not compromising the level of our platform. I added some steel framing connectors above the lag screws to protect the wood from wear over time.
In the end, it seems like a lot of work just to hang four boards on a tree, but given the importance of the foundation, it was well worth the time to get this right and feel good about what is to follow. More to come as we get into the second phase, and the challenges of securing the platform to the joists.