The type of reinforcement employed and the blend of the bituminous coating are critical to the success of the roof system.
Built-up roofing felts and modified bitumen roof membranes are both made up of two equally important components: reinforcement and bituminous coating. The type of reinforcement employed and the blend of the bituminous coating are critical to the success of the roof system. In recent years the types of products used in these components have changed due to a combination of technological advancements in the manufacturing process and extensive research and development on the part of roofing material manufacturers. These advancements have led to membranes and felts that provide higher performance capacity and longer life spans-elements that are critical in satisfying today's increasingly demanding building owners.
The most common types of materials used for reinforcements in these systems are now fiberglass or polyester. This is a departure from traditional BUR felts, which had used organic felts as the traditional reinforcements for built-up roofing for over 100 years. They were typically composed of organic materials, such as jute, animal hairs, shredded fabrics and cellulose. Cellulose fibers were initially made up of recycled newspapers and sawdust. Over time economic variations and material shortages led to the introduction of fiberglass felts in the marketplace. Over a 30-year span they slowly gained prominence to the point where organic materials were relegated to primary use in coal tar systems where the porosity of fiberglass felts created concerns. Polyester reinforcements were introduced into the market in the 1970s and early inclusion was in modified bitumen sheets.