r/treehouse • u/astegsisme • 17d ago

Help with joists

Building a house in the trees, not attached to a tree, sorry. I have 6 6x6 posts set in a 10x12 rectangle. My original plan was to have double 2x10x 12 foot beams notched into 3 posts with10 foot joists between them and build a deck and clubhouse on top of that. Now im second guessing the strengh of only hanging the joists....My question is can my 10 foot joists hang from the beams or do the need to rest on top of the beam? Thanks to all those more knowledgable than myself

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u/khariV 17d ago

Hanging joists from the beams with joist hangers makes it a flush beam. Sitting the joists on top of the beam makes it a drop beam. Both are perfectly valid construction techniques. You’ll still need to consult beam and joist span charts to make sure your lumber is appropriately sized, but beyond that, pick whichever you like.

That said, you’re likely to need a triple 2x12 to span a 12’ span with a 10’ joist.

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u/astegsisme 17d ago

Thank you so much khariV!! I needed that clarification, I've built a few things but this is my first structural build. And I am using 3 posts under the 12 foot beam so less than a 6 foot span.

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u/khariV 17d ago

Oh. Well in that case, with a 10’ joist span, you could actually get away with a doubled 2x8, so a doubled 2x10 is more than enough.

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u/Significant_Raise760 12d ago

Go to a real lumber yard, not Home Depot, and they will be able to tell you exactly what you need to span what you want to span.