a waterproof sheet used to waterproof structures has a single layer of non - degradable , water impermeable polymeric membrane that has layers of particles of non - hydrated sodium montmorillonite adhering to the membrane in a uniform layered thickness . the layers of particles of sodium montmorillonite spaced from the membrane adhere to each other , with a coating material that is designed to provide the necessary performance for waterproofing . a water soluble dye is provided in the layer of particles so if a tear occurs in the impermeable membrane and water contacts the particles , the dye will stain the membrane and mark the location of the tear .