Adding the second floor to the ham shack ( my third tree house ) in 1978. The first floor was constructed in 1977. It was a unusually  warm winter, and I was able to nail on through. The tower is bolted to the north wall, just to the right of me. Elevation 1600ft. The lumber was very inexpensive as I cut the spruce and hemlock on site to lengths 6 inches longer than I wanted and the local one man sawyer picked them up and returned the soaking wet lumber the same day. Close your eyes when nailing !