Lilyota
RIP 7/22/2023
I have an old friend that does tile.Man I'd say 90% of homeowner built showers are incorrect. No waterproofing membranes, usually the pan liner corners done wrong etc. Red Guard, Kerdi systems etc are the way to go. People don't understand and kind of hardibacker or concrete board is not waterproof, and in fact acts as a sponge. Even the OG showers back the day had plastic behind the backer board, or deck mud walls that overlapped the, (at the time, usually lead) liners. Anything with no waterproofing on the walls will have mildew and moisture behind the walls 100%.
He referd me to the Kerdi board.