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Im spanning 15 ft on 2 trees the house will be 12x15. how big should my beams be? this info is nowhere.


  • This is a large span to make with no additional support along its length. I'd suggest consulting with a professional treehouse builder or structural engineer to determine the size and material of your beams. They will be able to make a calculation based on the weight of the treehouse and occupant capacity, as well as determine the correct fasteners to safely carry what will be a heavy structure.

    The beams also need to be able to take up the movement of the trees in the wind and this will need to be factored into the design of the complete platform.

    The complicated nature of large spans is why this information is not available as a simple list.

    If you are building with posts for support you can find tables for span guidelines for deck beams online, however you will be using a significantly heavier load with a treehouse of this size. Further professional advice would still be recommended.
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