Tile and grout are water-permeable decorative finishes; true waterproofing relies entirely on the sub-tile moisture barrier adhering to ANSI A118.10 standards.
1. Sheet Membranes vs. Liquid Elastomers Compared
| Waterproofing System | Thickness Consistency | Curing Time Before Tile | Vapor Permeance Rating |
|---|---|---|---|
| Bonded Polyethylene Sheet (Kerdi) | Factory uniform 8-mil (0.2mm) thickness | Immediate (set tile into unmodified thin-set) | 0.90 perms (Qualified vapor retarder) |
| Liquid Roll-On (RedGard / Hydro Ban) | Variable; requires wet film gauge (30-35 mil wet) | 4 to 12 hours between 2 coats | 1.2 to 1.8 perms (Varies with thickness) |
| Traditional Mud Bed + PVC Pan Liner | 40-mil PVC sheet under 1-1/2" sloped mortar bed | 24 hours for mortar bed to dry | 0.05 perms (Clamping ring drain required) |