First process tear out concrete. Second step install plumbing for shower, sink & toilet in open floor, pour concrete. Third step seal outside wall with drylock water proofing and frame in all walls. Glass block windows before & after. Fourth step Installed electrical,heating, plumbing,insulation and 6 mil plastic to keep out moister on outside walls,then drywall. Fifth step mud,tape & sand drywall. Install1/2inch concrete board in shower,tape all seams & thinset all seams Add new concrete to shower & bathroom floor to level floors to make tiling surface flat and level.Install shower drain.Sixth step: Paint rubber seal on shower floor for leak protection, two coats forms a rubber seal like a liner.Lay out pattern on floor and walls. All lines must be straight and level. use a chalk line and a 2 or 4 foot level and mark with a pencil. mix thinset to a peanut butter consistency and spread using a 1/4 inch trowel.use non sanded grout for 1/8 inch spacing or follow instructions on grout bag.Seal all corners with silicone caulk that matches your grout color. Install shower door & bathroom door. Paint walls using a paint with primer in it & install heat register cover.