My kids' tree house is going to be 9' above the ground. I didn't want my 3yr old climbing a 9' ladder or staight stairs. So spiral stairs was the way to go. Materials: 3.5"OD X.25"wall X 16' pipe 3.5"ID X .25"wall X 82" pipe 2" X.1875" square tube 60' 1" pipe 50' .5" double braied polyester rope
3.5"OD pipe made up the mast. The collars for each step are a slip fit over the mast, 2" square tube welded to each coller made up the step support. 2X12's made up the treads. Each collar has a 3/8 set screw to locate then drilled 2 hardened steel pins to lock each step into place. Ballusters are 1" pipe with eyelets welded every 6". Double braided poly rope ties each step together. Steps are rated for 450lbs each.
Miller 350P. chop saw, drill press. hand drill.