Modified Bitumen vs Thermoplastic Polyolefin (TPO) Roofing Systems

October 7, 2019

There are two main commercial flat roofing systems that are commonly used in Northeastern North America are modified bitumen and thermoplastic polyolefin (TPO). They were both developed to address the issues with using traditional asphalt. Both systems work well in extreme temperatures, whereas traditional asphalt may develop cracks. Both types of roofing help to protect the roof from the weather, including blocking moisture. Each type of commercial flat roofing has it’s own pros and cons, and we’re going to be discussing some of the key differences.  


What is Modified Bitumen?


Developed in the 1970s, modified bitumen was designed to improve the standard asphalt roofing that was used widely during the 70s. So, what are the key differences between modified bitumen and asphalt? Modified bitumen IS asphalt, combined with a rubber or plastic to help improve flexibility. Roofers will use torches, or hot air welders, to join the seams of the material. This method creates a water-tight seal that will reduce instances of mold or rot. 


Properties of Modified Bitumen


Modified bitumen is a good material to use in areas that experience severe temperatures both hot and cold. It is a uniform material that is monitored for quality control, which helps roofers to plan for installation with ease. Modified bitumen can be used as a cap sheet for a built-up roof system. The combination of these two systems is called a hybrid roofing system. 


What is Thermoplastic Polyolefin (TPO)? 


TPO, also known as single-ply roofing, is made of sheets of a plastic membrane. These are welded together using hot air tools. This forms a barrier against water and can prevent problems such as rot, mold, and leaks. This system was designed in the 1990s to be a replacement for asphalt and modified bitumen, but it has yet to fully replace either product. 


Properties of Thermoplastic Polyolefin


TPO is a lightweight material that is quick to install compared to other flat roofing systems. It is considered energy efficient due to the reflectivity of the material. It can help to cut down on HVAC fees. Like modified bitumen, is is a uniform material that helps make planning a new roof instalment simple. One major potential problem with this system is it’s susceptibility to tears and punctures. It is one single layer, and if punctured or torn can lead to rot inside the roofing system. 


The Bottom Line



The benefits and reduced cost of modified bitumen make it a good candidate for most flat roofing systems. TPO is a newer technology, but the benefits may not outweigh the potential problems for most consumers. The single-ply material can rip, leaving the entire roofing system susceptible to moisture-related problems. Both products can be installed using hot air tools and modified bitumen can be installed with hot torches. Before you have any work done, make sure to consult with a professional roofer and have them outline the pros and cons of the system they intend to use for your new roof. 

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