We have a sagging ceiling. The tongue and groove boards(tiles?) that are made of some kind of foam/cardboard are coming away from the ceiling and sagging terribly. We have braced it with some wood for now, but it will fall soon. The ceiling is vaulted and there is no attic above. We have tried to find joists, but the "Stud Finder" does not register. We have tried to screw nails and screws into it, but it does not attach and leaves a mark/hole in the fragile boards. (This is the kind of ceiling that looks like wood flooring, but white and not made of wood.) My husband is out of work, so there is no money to rip it down and replace. Also, the previous home-owner (who installed) did not leave any extra pieces. Any suggestions???