Help with patching hole in wood subfloor in bathroom
We live in an older home and have tiles in the bathroom floor. Near the bathtub there is a spot where the tiles were loose, and we found that the tiles easily came up. Underneath, there was wet, rotted wood, because water has been getting into that area. There is also a long tunnel-like hole (2 in. wide, 2 in. deep, and 10-15 inches long) where the water has flowed through. We would like to patch the tunnel hole and then find some way to put the tiles back . Any ideas about how to patch this hole?? What sort of material should we use?
And then what should we cover the hole with in order to prevent further water from getting down there?
To complicate things, some of the tiles have uneven heights of cement board stuck on them, and we are guessing the cement board was the original base to which the tiles were glued. So we need a creative idea about something we can glue the tiles back onto after we patch the hole -- and something that can accommodate the tiles with multiple thicknesses of cement board.
Any responses would be greatly appreciated!!