Looking at treehouse plans online - sometimes you see joists on top of the support beams, sometimes it's all one layer using joist hangers. Is it best if joists are on top or does it matter?

Here is my plan... Beams are 2 laminated 2"x10"'s on each side - each floating on treehouse attachment bolts. 2"x8" joists on top using hurricane ties. 4 4"x6" knee braces below - 2 on the beams, 2 on the joists (via a horizontal 2"x8").

My Current Plan

Alternatively, do I make the beams/joists all one layer? Maybe everything is 2"x10" like this:

Alternate Plan

1 Answer 1


Joists crossing on top of beams is much stronger.
this is because when joists are butted up to beans they are flexible at the join.

I would try to avoid nail lamination in an outdoor location and instead use full-size beams and joists, if the beams must be laminated seal the top to keep rain out of the crack.

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