I am renovating a bathroom. The dimensions of bathroom are 5' x 10'. There is a 1/2" slope from the exterior wall across the 5' span to the interior wall. Before I put in my three-piece, 36" X 36" shower unit and the other fixtures, should I level the floor using leveling compound prior to putting in a tile floor and the fixtures. Another question is, if I need the leveling, do I need to put in the third shower wall containing the plumbing before the leveling or on top of the leveled floor?