To limit the probability of the vertical or horizontal migration of water within roofing membranes, which could lead to the leaching of bitumen, which could lead to inadequate tensile strength, which could lead to the premature failure of membranes, which could lead to water penetrating directly to roof decking or sheathing, which could lead to deterioration, which could lead to the structural failure of roofs or assemblies protected by roofs, which could lead to harm to persons.