We used the trees around the stump (the fairy ring) as the main supports for the very sturdy framing. Our research showed that drilling ALL the way through each tree was the best way to not injure them permanently.
Step 2: Spider web supports
My uncle's a building designer and he made sure this treehouse was up to code; estimates indicate we could build a 2-story house on top of the platform...
Step 3: Railing of copper pipes and salvaged bed posts
We used copper pipes for the railing as well as some old bedposts. All the decking (not the rails) are salvaged boards cut and sanded to fit. A big copper pipe became the fireman's pole, we bought a big cargo net, a local company donated rebar to secure the net in the ground, and we got a captain's wheel when we were in New Zealand.
Step 4: About 6 months well spent
Three years later and we still need to finish the steps (we want to refine the nailed down 2x4s) and one tiny board is missing because my aunt is crafting a woodburned heart with the names of the all the contributors.