Commercial and Industrial Roofing Services
systems: modified bitumen "built-up" roofing.
Overview
Modified Bitumen Built up Roofs are hybrid Conventional Built-Up Roofs in that they both consist of alternating layers of roofing felt and hot asphalt to “build up” the waterproofing layer. The difference is found in the material’s physical makeup– a polymer modified asphalt instead of a “straight-run” oxidized asphalt. There are two forms of modified bitumen; APP and SBS.
APP & SBS Modified Bitumen
APP (atactic polypropylene) and SBS (styrene-butadiene-styrene) are the two polymer additives that create the “modified bitumen”. Each has its own unique features, but both serve the same purpose; to dramatically enhance the weathering capabilities of the waterproofing asphalt.
The modified asphalts are combined with glass fiber to reinforce the membrane, which provides for very high tensile strength and flexibility, maintained even in the coldest winter months. A great advantage to the use of APP Modified Bitumen is capability of direct heat-welding application. This use is common in the installation of a two-layer modified bitumen system. The system involves a base layer of smooth, APP modified with a granular surfaced cap sheet heat welded to the base layer. This system in our specification is 315 mils thick and can provide building owners with a 20 year warranty. Guarantee aside however, you can reasonably expect to get 25-30 years before a drop of water will enter the building due to material deterioration.
There is a reason that this roofing system has been the clear choice for Chicago roofing for the past 40 years. It is tougher and stronger, pound for pound, than any other roofing system on the market.
We are proud to admit that we've also been singled out as one of the best installers of Modified Bitumen systems in the country by industry-leading manufacturers for the past 18 years straight.
A little pride never hurt anybody.
Additional Resources
APP Modified Bitumen Systems - An introduction to APP modified bitumen systems. Johns Manville Website.
APPeX 4.5M Modified Bitumen Product Data Sheet - Johns Manville Website.
Field Performance of Modified Bitumen - A research article published by the NRCA.