Aka Swimming pool/jacuzzi in the living room.
Reinforced the floors with 4 steel teleposts and boxed in the I-beams with 3/4" plywood as people had recommended. 2" plywood on top of the I-beams, concrete aka thinset, 6 foot steel mesh, more concrete, then marble/porcelain tiles.
Steel frame built out of 1 1/2" steel tubing. I think it's 3/8" wall thickness.
