I had a question about cork underlayment. Usually it is applied over cement, but is there any code or reason against having cork underlayment sit between a concrete basement slab underneath and a deck mud cement on top?
The next layer is a thin layer of Redgard waterproofing membrane on top of that, then a heated floor mesh w/ wire, then mortar, then ceramic tile.
Were you able to see how the cork was bonded to the concrete? If it had solid bonding, it shouldn’t be a problem.
I personally never used cork underlayment for tile, but I know they do make it for that.
There is a code requirement for R10 rigid insulation for heated floor (under concrete). I’m not sure if cork would meet that requirement or be suitable for this application.
Clarification - if codes requirements are important for you go to the code book that was adopted in your area. Codes can be very different depending on your location, especially energy codes.