Hybrid Tree House / Fort / Play Structure, my neighbor Nick and I had been discussing plans for something like this that all three of our kids could use. Finally we just sort of jumped in, made many decisions on the fly, but largely completely this portion in the past three days. To be fair, this is largely Nick’s project (it’s on his property) and he had way more time he could commit to it this weekend, but I pulled my own, fear ye not!
All told, that includes digging, plumbing and then concreting four 4x4s, each 8ft outside to outside to make materials lists easy / minimize waste, hung the deck @6ft with joists every 16, built around the tree trunk so it goes right through the house, dropped the decking, built railing, and a threw on a place holder ladder if something else comes down the line.

Eventually we will enclose the lower section, install a little half height door, and maybe throw a few windows here and there. Besides some 2-by spacers to help immobilise the deck against the tree, nothing else touches it, and nothing is screwed in to it.