|A simple treehouse, 6 feet off the ground in a willow with multiple stems.|
Choosing a tree
For any tree house, and especially your first one, selecting a tree that has a few branches radiating out at the same level will make things much simpler. For a first treehouse, a tree like a willow that splits low down is ideal.
The starting point, and the part that will probably take the longest, is getting your first pulley established to raise everything else up. A heaving line, with a weighted bag, beanbag or other weight with a lightweight messenger line will help you get the first ropes up. You can then use the first rope you establish to Prussik up and place a pulley for raising items up. Everyone working at height should be using harnesses and fall protection measures.
Rigging and raising the first pole is your next task. Once it's in place, and lashed onto the tree using hessian or padding, you can raise the rest of the base poles up and set them in place.
Having established the base, the next task is to get safety railing and any roof or other superstructure up. In my experience, you can expect to spend about a third if your time getting the pulley in place, a third of the time on the first two base poles, and the final third on the rest of the structure.