i figured i would build a frame out of 2X4s and lagbolt it onto the studs in the wall which allready exist
this would act as the support for two sides, then the stairs would support the other corner
i would then run 4X8 sheets of plywood in the opposite direction, over the new frame and existing "floor" to spread the load
because of the pitch of the roof, the headroom nearest the stairs will be the highest, and as you move towards the wall, it decreases, which will force the kids the hang out more in the area near the stairs
You can build the stair support and tread frames from iron. Sch.40 pipe and 1 1/2 angle Then do the treads and rail from wood. I've built over a hundred over my life time.
