Building designers across the U.S. would agree that it is crucial to select an appropriate weather (air, vapor, and water) resistant barrier in accordance to the standard code, to prevent water infiltration, and to control air leakage in a building envelope. There are three main types of WRB membranes that are commonly used: self-adhered, fluid applied, and mechanically fastened. In regard to fluid applied vapor permeability, there are two types of WRB: vapor permeable and non-permeable. This article will discuss fluid applied VP and NP membranes in thin and thick mil applications and highlight the advantages thin mil applications have over its thicker counterpart.
In manufacturing, mil thickness is a common measurement unit to describe the thickness of materials in thousands of an inch (1 mil = 0.001 inch). Thin mil systems generally refer to mil thickness of approximately 8 to 10 DFT (dry film thickness) and thick mil systems are approximately 40 to 70 DFT. Thickness and chemistry of coating formulations may affect many properties of installed systems, including air barrier assembly procedures, water leakage, weatherability, longevity, and durability.