The shower pan nightmare

Floor under shower pan
Originally uploaded by modernemama.

The terrazzo shower pan is no more. Steven drilled a couple of holes, hit a chisel with a hammer and used a sledgehammer vigorously for an hour or so and that base stood no chance. I'd been dreading tackling this beacause I'd heard horror stories about how difficult they were to remove. It turned out to be fairly easy. That was the best part of the day.
The second good thing was that forty minutes after ringing to enquire about dumpsters (skips) we had one sitting on our drive. And two hours later we had just about filled it.
It was far harder carrying the lumps of broken terrazzo out to the dumpster than it was breaking the shower pan up. That stuff is heavy. But here's the scary bit: the pan was just resting on the floorboards. No plywood reinforcement, no tar-paper or liner. So when you break up the shower base tiny pieces of terrazzo rain down through the cracks in the floorboards onto the bathroom ceiling below. And when you switch on the light in that bathroom you realise that not only does that no longer work, but the fan has stopped also.
Now my problem is that we still have to take up the cement floor tile bed. I imagine that this has a liner because otherwise what stops the mud falling down the spaces between the floorboards? But what if it doesn't? How much debris can I afford to let fall onto the ground floor bathroom before the ceiling collapses? The nightmare continues.....