can wood deck boards be installed over Hardiboard on balcony?
Although hardibacker board is a superior underlayment material for waterproofing I don't think it's designed to actually have water sitting on it very often. It is mold resistant but in reality it doesn't see water very often. I think the porous surfaces would fill up with organic compounds and allow mold and other funk to start growing. That being said I don't think I would remove it I would consider covering it with a smoother waterproofing membrane like Blueskin. Just to clarify covering it with the deck will allow dirt water and debris to accumulate and that will make short work of the grout. Then you've got a bigger problem, especially in cold climates. Water will work its way in freeze and pop tiles are so on.