A House In The Trees: Part I

My wife and I have three (3) sons, ages 7, 7 and 3. They destroy a room in a matter of minutes when they “play.” Luckily, the basement is finished and serves as a playroom. We can shut the door and the mess goes away. Unfortunately, the noise doesn’t go away. Since the weather turned last fall, we’ve been eagerly awaiting the day when we can send them outside to play. As an incentive to get out of the house, we decided that it was time to build the tree house.

When she thought it was time to start building, my wife brought the Black & Decker The Complete Guide: Build Your Kids a Treehouse home from the library. I went through it with a slight skepticism. I can’t say I’d trust a Black & Decker branded book to be all that good at any topic. While I feel my initial skepticism stands regarding the book’s production values, I was pleasantly surprised by the book’s technical information, especially its section on attaching to the trees.

I knew that when attaching to the trees it would be important to properly support the tree house, not kill the tree and allow tree house and tree to move independent of each other. The Platform Ancoring Techniques section was fantastic. It reviewed the entire anchoring process. After reviewing the section multiple times, I thought the solution would be the commercially available Garnier Limb anchors they mention. Unfortunately, when the anchor and associated bracket are priced out, it comes to $125.00 per attachment point (plus the special drill bit you need to rent or buy). This was more than we were willing to spend, so I set about building my own.

The Garnier Limb from treehouses.com
Since I couldn’t source such big bolts at the local hardware store, I began by ordering some ¾” x 10” galvanized lag bolts from McMaster-Carr. In order to transform these into homemade Garnier Limbs, I added two (2) galvanized washers and a length of ¾” galvanized pipe between them. After they were assembled, I think the homemade bolts came out pretty well.
The 3/4" x 10" galvanized bolt.

The washers and 3/4" galvanized pipe ferrule installed to form my
homemade mounting bolt.
I'm using commercially available post straps from Home Depot as the
bracket that will attach the joist to the mounting bolt while allowing
bi-directional movement.
Before installing the bolts, I glues together double 2x8 joists to form the perimeter of the platform. One laminated joist each at 10’, 12’ and 16’ long.
Gluing the joists.
In order to install them, I first picked and marked a height on the first tree (I was not particular about the exact height, as long as I could walk under the tree house). Using my right angle drill and a 9/16” auger bit, the 6” deep hole was easy.
This drill is one of my absolute favorite tools.
Then I set up my laser level and transferred the height to the remaining two (2) trees. Since it was getting late I decided to drill the second hole in the first tree and see if I could get the anchors installed. After drilling the second hole just like the first, I started ratcheting in the bolt.
That's as far in as I could get, using a 9/16" pilot hole.
It was about 2” in to ratcheting in that first bold that I realized a 9/16” clearance hole was too damn small for a ¾” bolt. I drilled out both holes to ⅝” and both bolts when in like champs.
Finally, a rock solid anchor bolt.
With the joists glued up, the first two (2) bolts in and the other trees marked I called it a night. More tree house building to come. In the mean time, here's a quick video showing the bi-directional movement of the mounting bracket system I'm using.