Greenhouses, Sheds and Sun Rooms - Sunroom subfloor rotted

We have a sunroom on our cement balcony in a highrise. A sub floor of rigid blue insulation was put down and then a layer of plywood. The sunroom was installed on top of this floor. Apparently the floor and the flashing at the outside edge of the sunroom were not sealed properly and water has seeped in from the bottom and has rotted out the plywood. If I remove the rigid insulation and the rotted wood there will be nothing to hold up the glass walls. Could I shim the wall in several places, remove the rotted wood and insulation and then fill in the gaps with expanding foam insulation and caulking? Then build a floor inside the perimeter of the sunroom? Or am I destined to have the whole room rebuilt and would it be worth it?
Any suggestions?

Thanks,

Welcome to the forums! Your sunroom was built to doom. Placing wood, even with a sandwich of foam, directly over a concrete stratum will cause the problems you have encountered with or without leakage. Now, to rectify it....If at all possible, remove the flooring and foam. Hopefully the bottom plates are of pressure treated lumber. The wood under the plate should also be removed and replaced with pressure treated dimension lumber possibly 3/4" or 1x4 (unless the room can be allowed to settle the thickness of the original flooring). The bottom siding should be removed and proper flashing applied up on the wall at least 8 inches and allowed to extend over the plate area on the outside, allowing the siding to cover it up without nailing into the bottom part of it. Expanding foam is great insulation, but is not a waterproof barrier, so don't use it.