Are you tiling a shower or tub, if so another expensive area due to waterproof backer membrane.

A contractor or inspector can tell you the problem.You can use a backer board or rubber membrane but that will only mask the problem.

NASA lives at the whims of the white house's plans for space travel (that prospect looks like it is picking up) Take me with a grain of salt since I am brand new to this and just starting to look but I'd be happy to answer anything i can. 

Insane in the membrane 

They're inexpensive like a rubber roof, but the seams get welded so it's very durable like a PVC membrane.

Hardest part is kitchen and utility room have oak hardwood floor under existing old style linoleum and has to come out,,,replaced with 3/4" plywood,,,then Green E underlayment ,,,then I use a water barrier membrane then tile and of course grout.

No way I would let anyone do this...if you penetrate the membrane below, it’s guaranteed to leak.

Spent $70,000 replacing a full roof (took everything off and all new joists, plywood, membrane, etc), building out a one bedroom one bath apartment with a full kitchen.

To be safe with anything except a fairly new house, you’d really need to excavate around the house, parge the outside of the foundation with an asphalt/tar product, install a dimpled plastic membrane over that, and then on the inside, fastidiously install rigid foam on the floor and walls, spray foam/tape all seams, etc… Then frame, then drywall.Seems ungodly expensive.

Due to the wood subfloor, the bathroom floors have a little give to them and one of the small tiles is cracked. not a big enough deal to replace (2 inch tile) but knowing how difficult it is to stabilize old wood floors with the seasonal temperature/humidity changes in our area...we'll be doing allure in the future.Thats one reason to install a crack isolation membrane before tiling.