2021 IRC (International Residential Code) | Chapter 27 Section P2709 Shower Receptors
P2709.1 Construction. Where a shower receptor has a finished curb threshold, it shall be not less than 1 inch (25.4 mm) below the sides and back of the receptor. The curb shall be not less than 2 inches (51 mm) and not more than 9 inches (229 mm) deep when measured from the top of the curb to the top of the drain. The finished floor shall slope uniformly toward the drain not les: than ¼ unit vertical in 12 units horizontal (2-percent slope) nor more than unit vertical per 12 units horizontal (4-percent slope) and floor drains shall be flanged to provide a watertight joint in the floor. P2709.2 Lining required. The adjoining walls and floor framing enclosing on-site built-up shower receptors shall be lined with one of the following materials: Sheet lead. Sheet copper. Plastic liner material that complies WithASTM D4068 or ASTM D4551. Hot mopping in accordance with Section P2709.2.3. Sheet-applied load-bearing, bonded waterproof membranes that comply with ANSI A118.10.