I am planning on remodeling our shower. The current shower was built poorly with no vapour barrier. Once I ripped out the old vinyl like layer I found dry wall behind it. The plan is to take the dry wall out up to the shower length and then add cement board(HardieBacker). After that I am planning on installing Schluter®-KERDI-DS waterproof membrane. Lastly we are planning on installing the porcelain or ceramic tiles on it. My few concerns are as follows: a) Is this a good design to implement or am I missing something? b) Should I remove the complete walls or only to the length of shower (pic img_0511)? Pictures attached for review. I heard mixed thing on the internet and I wanna make sure I do the right thing. Thanks for all your help.