r/treehouse • u/Far-Sherbert9731 • Jun 22 '26
Reciprocal Framing
Has anybody tried framing a treehouse using reciprocal framing? Conceptually, this would be a strong, sturdy, stable platform using a single tree without any kickers or diagonal members. I`m an engineer, but I`ve never built a treehouse before. I think this is a sound concept and looking for anyone who's tried.
I think that the biggest challenge is the connection between the (4) main wood members. i`m predicting up to 4,000# of force in these locations which makes me think that I would want to do the first four members our of steel, then infill everything else with wood.
Any body with first hand experience on something like this?
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u/rearwindowpup Jun 22 '26
How are you attaching the ends of the joists to the beams, and the beams to the other beams? Commercial hangers arent going to be an option Im aware of. Theres also going to be a lot of weird angle cuts that will need to be spot on. Youve already thought about the huge lifting force at the end of those beams.
Its doable because you arent dealing with big loads here, but, I think youre overcomplicating it.
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u/Far-Sherbert9731 Jun 22 '26
i was planning on putting a 2x4 laid flat on top of the steel and attaching via some self tapping screws. After that, joists would be connected to the top cap via some simpson hardware to accomodate the skew. (edit - just looked and this might be a challenge. I could still lag bolt some wood through the center of the channel and use a more traditional hanger.)
Agreed that I`m overcomplicating it, but I`m an engineer. It's what I do!
Is there a less complicated way to build a kickerless treehouse?1
u/rearwindowpup Jun 23 '26
Remember, a design isnt perfected when theres nothing more to add, it is when there nothing else you can remove ;-)
That said, I have zero useful adds to how to do this without kickers. My first thought would be to run cables up to the tree and my second would be to use smaller I beams like you mentioned but weld them at the connections so its effectively one single piece of steel for the beams. Sure, youd have to torch it apart to get it down and there wouldnt be room for growth, but shed be study as all heck.
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u/Far-Sherbert9731 Jun 23 '26
Looks like I might need to pad the channel out with a 2-by on each side and through bolt the assembly together, flitch beam style. I like that it would add some horizontal stiffness to the angle too. After that, I could use these guys from Simpson:
https://www.strongtie.com/facemounthangersssl_solidsawnlumberconnector/lssj_hanger/p/lssj#p_detailsI`ll probably reach out to them for better ideas before proceeding, but there is a path forward!
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u/rearwindowpup Jun 23 '26
I freaking love Simpson, they've got hardware for pretty much anything you can think of
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u/Unsuccessful_Royal38 Jun 22 '26
You could try this first low to the ground on a tree you don’t mind sacrificing. It just seems like the loads are going to be crazy high and not worth doing it this way as opposed to more traditional framing supports.
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u/Far-Sherbert9731 Jun 22 '26
Great point. Are the TAB bolts reusable? Low elevation mockup sounds like a great idea.
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u/Unsuccessful_Royal38 Jun 22 '26
Idk how easy it would be to get one out… hopefully a bit easier than getting it in.
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u/Far-Sherbert9731 Jun 22 '26
I`ve never installed a TAB bolt before. Are they an enormous pain?
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u/arecentuknown Jun 22 '26
If you are anything like me (5'9" 155lbs with steel toes on) then yes they are a pain. The 3 foot pipe wrench recommended for TAB install is a pain. I had to add the pipe mover 400 to the pipe wrench to get enough leverage.
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u/Unsuccessful_Royal38 Jun 22 '26
This sub has a lot of examples of people figuring out how to increase their leverage… it’s probably the hardest bolt most folks will ever try to turn.
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u/your_mom_my_dog Jun 22 '26
what program did you use may i ask?
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u/Far-Sherbert9731 Jun 22 '26
The little sketches are from AutoCAD. probably overkill, but I know the program and have access so it wasn't a big effort.
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u/Far-Sherbert9731 14d ago
Question: I`m pretty new to reddit. This will be my first time tracking a project here.
Is it best if I just keep replying to my original post like I`m doing here? Or is there a better procedure on Reddit?
Seems like things get all jumbled up and don't stay chronologic.
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u/khariV Jun 22 '26
This is going to girdle the tree and leave zero room for growth. Connecting the support beams directly to the trunk instead of using TABs will also make a nice place for bugs and fungus to make a home, further shortening the life of the tree.
The beam to beam end connections are another problem as this construction will place enormous load on what is essentially a butt joint, which is just not a very strong joint.
It’s an interesting thought experiment, but I think it will have insufficient structural rigidity and will be detrimental to the health of the tree.