A flexible rubberlike material used in tiled tub and shower installations, and also in thickset counter installations.

A polyethylene film (usually 4-mil thick) or tar paper installed to prevent moisture condensation or penetration. Also called a vapor barrier.

A membrane, usually made of built-up roofing, to provide a positive waterproof floor over the substrate, which is to receive a tile installation using a wire reinforced mortar bed.