TPO vs. Modified Bitumen Roofing Systems

Choosing the right roofing materials is critical when it comes to commercial and industrial buildings. Two popular options in the market today are thermoplastic olefin, also known as TPO, and modified bitumen. In this article, we will explore the difference between these two materials by discussing their pros, cons and the installation processes.

TPO Roofing Systems

TPO is a single-ply membrane made from a blend of polypropylene and ethylene-propylene rubber. It comes in sheets that are attached to the roof. TPO material has been used on commercial roofs since the early 1990s. Since then, it has become increasingly popular due to its durability, energy efficiency and ease of installation.

Pros of TPO Roofing

Energy Efficiency: TPO membranes are usually white and highly reflective to UV rays, making it an excellent option for reducing heat in buildings which helps lower cooling costs.

Durability: TPO is resistant to UV rays and chemical exposure. It’s also less likely to break down under harsh weather conditions or extreme temperatures, making it a durable option for many environments.

Flexibility: The material is flexible, allowing it to accommodate to a building’s movement or settling over time without damaging the roof. This flexibility also means it can be fitted around various roof accessories and penetrations easily.

Ease of Installation: TPO membranes usually come in wide sheets, which means fewer seams for a quick and less complicated installation process. In certain cases, TPO can be applied to the existing roofing system. This can reduce the cost of labor and material.  

Cost-Effective: TPO roofing is a more affordable option compared to many other types of roofing systems, making it a popular choice for large commercial buildings.

Cons of TPO Roofing

TPO is a single ply membrane which means you will have problems if it is punctured. This system does not have an extra layer of protection at the surface.

TPO needs to be installed by an expert. It is important that you find a qualified roofer, so you don’t experience bubbles in the membrane which lead to leaks and a short lifespan.  

How is TPO installed?

The TPO membrane is unrolled and cut to fit the roof. It’s typically installed using one of the following three methods:

Mechanically attached systems use plates and screws to attach the membrane to the decking at the seams.

Fully adhered systems use an adhesive that is applied to the decking and the membrane to bond the two together.

Ballasted systems pour gravel over the membrane. The weight of the gravel holds the membrane underneath in place.

Modified Bitumen Roofing Systems

Modified bitumen is an evolution of traditional asphalt roofing. MB uses modifiers such as polymerized rubber or plastic that is reinforced with fiber glass to enhance flexibility, durability, and performance. It is typically installed in multiple layers, creating a robust and long-lasting roofing system.

Pros of Modified Bitumen Roofing

Durability: Modified bitumen roofs are known for their tensile strength and durability. They are resistant to common forms of damage. Modified bitumen is resistant to punctures, tears, and extreme weather conditions, making it an excellent choice for high-traffic or demanding environments.

Easy Repair and Maintenance: Repairs on a modified bitumen roof are relatively easy and can often be performed without professional help. Regular maintenance is straightforward and typically involves clearing debris and checking for signs of damage.

Highly Resistant to Water: Modified bitumen roofs offer excellent waterproofing characteristics. The material’s seamless installation helps prevent leaks and provides excellent protection against water damage.

Cons of Modified Bitumen Roofing

Installation Complexity: The installation of modified bitumen typically requires more labor and specialized equipment, leading to higher installation costs. It is important that you get an experienced roofer to install this system correctly.

Cost: Due to its multi-layer construction and complex installation, modified bitumen can be more expensive than other roofing systems.

Heat Absorption: Traditional black or dark-colored modified bitumen roofing can absorb a significant amount of heat from the sun, potentially increasing cooling costs during the warmer months. However, many manufacturers now offer “cool roof” coatings or lighter colored options to mitigate this issue and modified bitumen comes in lighter colors that don’t absorb as much heat.

How is Modified Bitumen Installed?

Modified bitumen usually consists of two layers known as the base sheet and cap sheet. The base sheet is attached to the roof substrate then the cap sheet can be applied with an adhesive or torch down. Adhesive applications are a lot easier and safer than torch down applications, as they do not require extreme heat from a torch to apply the roofing membrane. Typically, they will have a sticky layer on the bottom that you can peel back. On the other hand, torch down applications require extreme heat to apply the membrane to the roof. You will need a roofing expert to do the torch down application safely and efficiently.

Depending on the location and function of your building, TPO or modified bitumen may be the best option for you. As a licensed, professional commercial and multi-family roofer, Corey Construction can help you determine which is the best system for your building. If you need a commercial roof installation, roof repair, or roof replacement, we have expertise in both TPO and modified bitumen roofing systems. Contact us for your next roofing project estimate.

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