Gyprock ceiling is falling down, due to ground movements; clay soil. I am informed that the ceiling is attached to beams by studs(?). Inspecting the roof cavity is difficult as it's a flat fibro roof. Since the split in the ceiling is so large, can see, two beams/joists/battons coming across; not sure whether these are the same timbers that the gyprock is attached to, as the distance is greater than it should be(?). Question: how much room is there between timbers coming across supporting the roof; and those supporting the gyprock ceiling? Trying to identify timbers that the gyprock should be attached to. Using a stud(?) detector, not sure what range this has, and what it is detecting. My only solution thus far is to use 100mm scews (longest that can be purchased) and use these to attach to the two timbers referred to. The two timbers are approx 2inch by 1 inch, they are approx
3 inches apart and positioned thin edge up.Any recommendations re. this repair; thanks.