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I'm building a 7 x 12 tree house platform on a single tree.

The layout is one tribeam Attached to the tree with tree house attachment bolts. Then in front of that are two 6 x 6 posts with a 4x6 beam going across. The bottom of the tribeam and top of the post beam are parallel. I’ve laid my 2 x 8 joists on top of the beam in front and attached to the tribeam with joist hangers (in retrospect would’ve made more sense to lay joists on top of tribeam but too late for that now)

Question: To allow for a tree growth/movement, should I attach the joists to both beams or just leave the joists floating over the posts.

overview of tree house construction so far

under deck view identifying joints in question

Chris
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  • This question would benefit from a photo of your situation and layout. Feel free to mark up (draw with Paint if you have nothing else) to indicate missing elements or the part of the configuration you're asking about. – Fredric Shope Mar 07 '22 at 22:52
  • See photos above. The hurricane ties are attached to the beam but not to the joists. Not sure if I should leave them floating like that to push out as tree grows or if I should fix everything down – Chris Mar 08 '22 at 00:07
  • Several questions. How long do you expect to use the treehousde? It looks like your attaching the tree hiouse to a pine tree of sort right? They tend to grow fairly fast, compared to a hardwood tree. Assuming the tree grows and the trunk size increases, where do you think the stresses are going to be? – SteveSh Mar 08 '22 at 00:28
  • Note, I built something similar 15 yeara ago. But moved away long before tree growth became an issue. I'll post some pictures if I can find them. – SteveSh Mar 08 '22 at 00:30
  • I’d like it to last at least 20 years. Yes it’s a pine tree I had no other options. If the tree grows and pushes forward, I didn’t attach the joists to the front beam, they are just floating on top. I could screw those joists in, just not sure if that’s a bad idea – Chris Mar 08 '22 at 02:45
  • I live in the Pacific Northwest and would never use a fur tree or pine, if you used a large free pin and the “small” tree survives and doesn't split it may last until the kids are grown make sure not to damage the bark and allow inches for growth or splits in the lower decking and a dead tree may be the result but even then it takes a few years. – Ed Beal Mar 08 '22 at 03:33
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    You're a long way into construction already, but it looks to me like you're just using the tree as a single post to hold up one end of the deck. It may well have been easier to have sunk 2 more posts for the back corners and left the tree out of the equation entirely - just make a cutout for the tree at its current size and enlarge the cutout in the future as necessary. – FreeMan Mar 08 '22 at 13:32
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    Given what you've shown, I would fasten the hurricane ties to both the joists and the beam at the far end, and let the joist float to some extent on the beam that's attached to the tree. That's essentially what I did with the tree house I built (see earlier comment). – SteveSh Mar 08 '22 at 15:21
  • @SteveSh Joists on tree side are attached via hangers to the tribeam so they can’t float. So I’m wondering what to do with the hurricane ties at the post beams – Chris Mar 08 '22 at 17:42
  • @FreeMan I did think of that but as you say, too far in now. If the tree ever became an issue couldn’t I jack up some new posts later? The TABs seem very solid and I don’t anticipate having an issue – Chris Mar 08 '22 at 17:45

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Manufacturer of the treehouse attachment bolt system says no need to keep anything floating on a one tree/two post treehouse.

Chris
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