I'm building a treehouse in a fully grown 50 foot tree that has four trunks (as it were) each of which is between a half foot to a foot in diameter. First, is this a good candidate for a small tree house (5×5 platform) that will be attached directly to the tree? If so, does anyone have any recommendations for supports in a configuration like that. I have some ideas but I wanted to get the opinions of people who have experience in contracting and even treehouse building.
Suggestions for treehouse platform support without posts
treehouse
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You certainly won't want to just sit the beam in the fork of the tree. The tree will move quite a bit and you'd slowly wear through the bark and damage the tree if you do that. Also note that forks aren't always the strongest part of the tree.
What you want to do is have the beam mounted to the tree with hardware that a) allows for lateral movement and b) is offset from the surface of the mark.
They make special hardware just for this. It's typically a huge lag bolt with a spacer than the beam 'rides' in via a slip bracket. Example:
source: http://www.treehousesupplies.com/1_25_Floating_Bracket_p/br-f1.25.htm
I think those are Simpson Strong-Tie HD3B, or maybe a HD5B. At under 10 bucks a pop, you can probably afford to buy one just to look at it and see if you think it suits your needs.
edit: just looked at the fancy $100 ones, and I can see how you get way better attachment from them. I suggest you integrate a strap that ties the bracket to the underside of the brace, as a single lag through the bottom of the simpson isn't going to be stellar at resisting a force that pulls away.
Best Answer
The Treehouse Guide is a pretty comprehensive resource. It covers topics from picking out the tree to building code adherence.