Brian I kinda get where you’re coming from because for years we did things that worked just fine and made sense. One problem we have here with this situation imo is that not everybody is doing things by the tried and tested methods of old. One of the biggest culprits is the manufacturers of the ply sheets we are offered to work with. They simply aren’t what they used to be. The quality of ply by and large now can’t be compared to the ply that would have been the bedrock of the construction industry whilst I was a tea boy. Taking that into account the substandard material that we now have on offer to us we have to evaluate it and consider if it is in fact the best option and to be frank nowadays it’s not. In years gone by I successfully tiled onto ply, as it WAS the best option, now due to penny pinching, technological advancements and market forces the general quality of the ‘ plywood’ that’s on offer today falls a long way short of its predecessor.
So on that note I have to reccomend that we no longer consider plywood to be the best or cheapest soloition as a substrate to
tile upon.