Commercial Modified Bitumen Roofing in Southern California
Dunlap Roofing Company
Modifiers are added to standard roofing asphalt to replace plasticizers removed during the distillation process. Bitumen is reinforced with fiberglass or polyester fiber matting in order to increase durability and strength. The two most common types are SBS and APP.
When added provides a plasticized quality to the asphalt. By adding 30% APP, the asphalt is able to be stretched up to 50% of its original length. The APP modified asphalt is reinforced with a polyester mat and manufactured into a roll product. These membranes have extra asphalt on the back side which allows it to bond to the substrate through applications such as heat welded or torch applied methods.
When combined with asphalt, produces rubberized properties. By adding 10%-15% SBS to the asphalt it is then able to be stretched six times its normal length and then can return to its original size once relaxed. This helps deal with the stresses of normal expansion and contraction of a roof. Reinforcements for SBS modified asphalt include fiberglass, polyester, or a combination of both. These membranes are most commonly applied with hot asphalt or cold adhesive. There are also self adhering SBS membranes, which contains an adhesive backing.