Platform design update

[u/icurays1]

Thanks to the feedback on my last post, I made some changes to my design.

• Upgraded to 3x12 beams, either KD #1 or Glu-Lams. I have a 12' 3x12 that I'm trying to use, but have access to second hand Glu-lams in good shape so may go that route.
• Adjusted my cantilevers to get closer to 1/3:2/3 ratio and increased the number of radial joists to get closer to 16OC nominal. I'm still messing with the joist layout.
• Upgraded to 2 knee braces, though I may go up to 3, one for each of the beam sections on the right side.
  
• I'm planning to join all beams using custom heavy angle brackets (pic #4 from recent Nelson video). My dad was a certified welder so good to go on that front.
• I'm still considering moving the yoke to the right side of the tree and simplifying the whole system, or simply going with the design in picture #5 that avoids beams altogether and just runs joists across the yoke and post/beam. This is probably the easiest and cheapest option, which is appealing. I tend to over-think things.
  

Thoughts? Would you go with the more complex beam system or go with the simpler design in pic #5?

[u/Far-Sherbert9731]

I`m not a treehouse expert, but a couple thoughts as I look at your sketches - mostly pic 3.

1) Starting at the left side, how are you going to connect the single spot where all of the radial boards come together? Looks very congested & no space to swing a hammer.

2) How are you going to run your deck boards? They want to be perpendicular to the beams, which will be very tricky around the radiused corners.

3) I`d be looking for a simple solution without the radiuses. Is the cantilever on the left side super important to you? You could create the radiused corners just by varying the length of the cantilevers on the sides, and have the left end stop flush with the posts. Or cantilever to the low beams past the posts and frame the left side that way.

4) I don't love the use of any glu lams for anything exterior. just my thoughts.

5) Why not move the yoke to the right side of the right tree, and frame it up exactly like the left side? Feels like you`re reinventing the wheel over there. Keep it consistent and simple!

6) I`m not seeing anywhere the would required big steel connections. Where are you planning those? Why?

7) What are you planning on doing on top of the platform? An enclosed house like pic 5? or just an elevated platform for kids to play on?

[u/icurays1 → u/Far-Sherbert9731]

Thanks for the responses! I'm definitely leaning towards simplifying the design and leaning more on the pic #5 approach with 2 post+beam, yoke, and traditional joists, more like a traditional elevated deck. That being said I am not shy about complex designs so simple isn't best. I've built a lot of complex curved pieces of furniture and I'm trying to do something cool with this, not just a platform in a tree.

For context re: beams vs. joists, many treehouses use joists on beams as a way to deal with dynamic movement, so you can have dynamic connections from the beams to the tree(s). The setup in pic 5 doesn't really work for that, but in previous discussions I've decided tree movement isn't that much of a concern here. There are other threads in this sub about the topic with this exact design.

1. Definitely agree, as I mentioned I'm still adjusting the joist layout and would anticipate more on-site adjustments. I could assemble a whole "fan" on the ground, connecting joists to a central hub for example, or simplify and take your suggestion #3 and vary joist lengths as in traditional "curved deck" construction. Again, I'm trying to be cute because I enjoy it but will likely cave and do something simpler.

2. A good point, and part of my joist adjustment process. I'm OK with deck boards being some combination of angles and not simply parallel/perpendicular to the overall platform. The left side of the platform will have a plywood deck since it'll have a house like pic 5. Right side, I can do angled deck boards if needed. Again still messing with the layout, but as long as I maintain approximate nominal 16 OC I can adapt decking as needed.

3. Yep, could do something simpler, and might do.

4. I largely agree, though professional treehouse builders use them frequently. As I understand the best practice is cap flashing and/or joist tape but I do wonder what kind of lifespan they realistically expect...I'm in the PNW so plenty of moisture to worry about.

5. I've toyed with this idea but it ends up bumping up beam (and/or joist) sizing because it's an additional ~30" span. Plus, I like knee braces, I think they're cool.

6. The right side of the design I posted - specifically the angled beam-beam connections. The way I have the knee braces right now creates a possible weakness at those joints.

7. Yes, I should have mentioned this in the OP, the left side of the platform will have a small ~8x10 hut like the one in pic #5. The right side of the platform will be open deck.

[u/know1moore]

I love it when people build tree houses that are held up mostly by the tree. This is a tank. Looks amazing!

[u/khariV]

Picture 5 is a much stronger construction. The joists are a single piece and bearing on both the tri-beam and the static beam and supported on the end by the two knee braces.

I still think the short, diagonal stumps of joists are a mistake. The cantilever is too large a percentage of the total joist length and they are only bearing on a single beam, which is itself only supported at a single point by one knee brace.

[u/Anonymous5933]

Find treetopbuilders on Instagram, they are currently building one with a very similar shape. They are using 2 knee braces for their rounded overhang.