I was wondering what kind of exterior drywall or cement board like the one used in this photo. (this one is taken from Pedro Calungsod Chapel in Cebu) The Column like structures are hollow. Will a 6mm thick Hardiflex/Shera Board Survive the harsh elements? Also, for the framing - will properly primed angle bars suffice and not be consumed by rust in this setup? I always wanted to build structures like this - quick, fast and clean installations vs tedious manual labor. thank you very much!