Roof construction
On the roof construction it is most probable of the three roofs the first layer would have been the original floor.Built in a period of cheap timber shipyards and many local sawmills in the area. There may have been extra beams to retain internal walls as well. Second roof would have been added after removal of second floor, but would leak after twenty years then the final roof added on top to fix the leaks. This almost survived the full crash impact and probably saved a few lives. The aircraft in no way had a controlled landing and damage is not due to the roof giving way.