Child tree house

You talkin a house on stilts or using an actual tree for the foundation?
stilts open to budget, tree dictates the size ie smaller tree smaller house.

Will you overspend haha, figuring a 100sq# lid (no permit here) that's around a 9x9 play space, think tiny bedroom.
Would a storage shed with a loft, work till outgrown, and switched to useful space later be a better setup...

Tree, probably 2 trees actually. I have 2 about 7ft apart, probably 14” diameter each

Win.
calculate the floor joist at +30 psf
Over build the deck, take into consideration the average expansion of the trunk and branches.

Planning one now. 16'x16' deck with an 11'x11' cabin. Both for the kid and as a guest house. That way I won't feel bad if he uses it like twice. I'm also going to build it modular- separate walls screwed together on top of the deck, separate roof trusses and then some translucent poly roof panels. That way I can move it or sell it later if I want

If you're using more than one tree you'll want to use a floating mount on one end at least so the tree sway doesn't fuck shit up. A tree is a looong lever. I'm going to use 3/4" x 12 lags, and probably a j bracket on the float end. Eyebolt with cable and chain is ok as well, some people just slot a hole, and I'm sure someone will sell you some fancy ass stuff if you want. One bolt per end- do not put more than one bolt within a foot or so of another or the tree may 'compartmentalize' that area and it could rot out around your hardware. Good idea to space out your beams from the tree- a short piece of galvi pipe and some washers on your lag works well. Good idea to use a safety backup as well, usually an eyebolt and cable. 14" tree is fine depending on species.

I have friends who saw lumber, so I'll probably have $250 into the deck materials. No idea what retail dimensional would run. Looking like about the same in hardware between lags, forged eye bolts, cable stuff, etc. I have builder friends and the all seem to have a window stash for personal projects they've offered up. Ask around. A treehouse needs windows, and free windows saves $$$ on sheathing. I'm going to use cool old single pane ones and hinge them at the top with a simple leg down bottom to keep them open.

Just some ideas. Post up as you go.