I am not much of a carpenter so I am sure my terminology is way off. Sorry for the confusion. By "cross members" I meant the short 2x6"s that connect the beams on either side of the 4" toilet line to form a box to support the toilet flange. The toilet is a full 2 inches lower than the rest of the room at this point so they must be in poor condition.
Your right I think about bolting the sistered 2x6"s. Maybe some very large washers on either side to distribute the compression load on the wood. I'll pick up the hardware this evening.
Also would you consider 3/4" treated ply to be an inferior sub-floor? Really what I am shooting for is a drastic over-engineering of floor strength. The wife is not a small woman and she has a tendency to dash into the bathroom and dive onto the toilet at the last second (which is why the flange was cracked and leaking).
Is there perhaps a covering I could put over and glue to the CCA stuff to help with tile adhesion? I suppose I could leave it exposed for a while and let it dry out some before applying the tile. This kinda brings back the health concerns with our son though.
Thanks for the tips by the way!
