Start of the Treehouse

Tree house. I’d talked to the kids about building one at our last place. At the start of 2017 we moved into a big arse joint that we went halves in with some mates. We have a pair of kids @ 4 and 6 and theirs are 4 and 8. This time a tree house will be built. I’ve done a lot of research so far as to the best way to build a tree house. The trees that will be used are below:

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From centre to centre they span about 4.4 metres. Not overly exact but for roughing up an idea that works. The internet reckons that attaching a tree house to tree should use as few as possible entry points into the tree. I don’t want to build one that is supported from the ground  so research led to Ganier Limbs – http://treehouses.com/joomla/index.php/construction/garnier-limb

These are specially designed bolts that you can attached a shit load of weight to support a tree house. The secret/beauty is in the 3″ boss to distribute the weight as this boss is housed in the tree, with a length of steel sticking out to hold beams. I live in Canberra. These come from the states. I like DIY and these cost upwards of $70 USD each (exchange rate ATM is .76),  so I started to build my own. M16 coach screws @ 200mm are how I will attach to the tree. Taking cues from the Ganier Limb, I will use a 100mm of 3mm walled pipe and have 50mm of that sit into the tree. 50mm will then be hanging out of the tree to mount 2 x 295mm x 45mm @ 4.8 metre lengths of treated pine to form the base of the platform.

I think this will be enough to support a decent side house. From http://quantise.com.au/nailing-it-with-bolts/ I get that an 4.4 grade M16 bolts tensile strength is 16×16/100 = 2.5 tonnes with a shear of 1.25 tonnes. This is the measurement I’m most concerned about, the shear. In my internet research I came across a fair few examples of coach screws failing under load. They were screwed into the tree with the shank of the bolt used to support the load of the tree house. To get around this, the coach screw will be used to hold the pipe in the tree, and the weight of the tree house will be carried by the tube instead of the bolt.

The new house hasn’t got room to add a 15amp circuit for the welder yet so I popped around to Dads place to start fabrication. I was hoping to get the brackets completed but we ended up with the below:

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I’ve since drilled the holes in the strap out to 16 mm and the coach screws shank fits perfectly. I’ll be back to Dads next weekend to weld them up:

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