I'm about to construct a loft bed as in picture: it's 240cm long and 180cm wide (7.9ft x 5.9ft).
The floor frame is composed of 2 main beams (2x6) that run on the longitudinal direction, and 7 joists (also 2x6), one every 40cm, attached to the beams with joist hangers. On top of that is a sheet of plywood 21mm thick.
The main concern is about the 2 main beams: is 2x6 enough to support the weight of all the joists (2 adults) or should I use 2x8? Do you think the flooring is ok or should I run the main beams in the short direction and the joists longitudinally?
I have also attached a picture of the frame.