The #1 Reason Why Modified Bitumen Is Better Than Single-Ply Commercial Roofing Systems

Modified Bitumen Commercial Roof

Since 1972, Modified Bitumen Roofing Systems have been one of the go-to options for flat commercial roofs. But with the rise of TPO & PVC commercial roofing systems, more and more commercial roofing contractors are turning away from the multi-ply commercial roofing systems, however here at Central Roofing Company. And there is a simple reason why. Let’s dive right in.

What Are Single-Ply Commercial Roofing Systems?

Whether you choose, TPO, PVC, or EPDM, they are all single-ply roofing systems. What that means is that sheeting is wide-width indicated for low-slope roofs.

Single-ply roofs have far fewer seams than asphaltic rolled roof systems and don’t require dangerous torches or hot asphalt installation. They also come with prefabricated detailing accessories that make installation easy.

What Is Modified Bitumen Commercial Roofing System?

To start let’s begin with what is “modified bitumen roofing. ” Mod-Bit” as it’s called in the industry was developed to replace the more costly and complicated Built-Up Roofing (BUR). Modified Bitumen Roofs are made with asphalt material combined with polymerized rubber or plastic.

This combination of either rubber or plastic is why it’s called “modified” because the asphalt is “modified” with either rubber (often called “SBS” in the industry) or with plastic (often called “APP” in the industry.)

It is a multi-layered system or “multi-ply” system because in most cases calls for at least two layers (a base layer and a cap layer) and in some cases a multi-ply system of three or more layers.

Additionally, it is installed in 3 ways, a torch-down method, a hot-mop method, and a cold adhesive method.

Why Do We Prefer Modified Bitumen Commercial Roofing Systems?

Multi-Ply System

Modified Bitumen is a 2 Ply or 3 Ply roofing system.  This allows it to withstand heavy foot traffic because of its thickness which is about 5 quarters. The thickness also comes with the added bonus of making it very puncture-resistant

Modified Bitumen Flat Roof System (1)In addition to its thickness, it is also flexible which allows it to endure extreme hot or cold temperatures.

Modified Bitumen Flat Roof SystemThe ceramic granular material that makes up Modified Bitumen gives the system added protection against ultra-violet rays from the Sun. 

Also, the seams are fused together with high heat to prevent any separation which creates a consistent and seamless connection between the sheets. 

Applied Modified Bitumen is hands down the cleanest finish, it has great puncture resistance, and is an equal comparison to Single Ply(thermoplastics) in workability with details. Single-ply is great if you upgrade to the Fleece back system. More mils and high puncture resistance too. Patching or repairs in my humble opinion are easier on single-ply.

Cool Roof Coating Option

Modified Bitumen Roofing Systems generally have a lifespan of about twenty years, however, you could extend the lifespan of the Mod Bit by adding a cool roof coating on the roofing system. 

Here at Central Roofing we prefer using silicone coatings on all of our roofing systems but that is not to say that acrylic coatings don’t work on these systems as well. Also, I have to mention that Modified Bitumen isn’t the only roofing system that can be cool roof coated because a cool roof coating especially silicone coatings can be applied to pretty much all the roofing membranes available on the market today. 

The Lifespan Debate

The general consensus is that Modified Bitumen Roofing systems don’t last as long Single-Ply systems. However, when installed correctly, modified bitumen roofs can last just as long as single-ply roofs. The key factors are installation and maintenance. Single-ply systems our newer on the market and many roofing companies often don’t install the system correctly which causes the single-ply to not last the length of the warranty period. The same can go with modified bitumen but modified bitumen has been around a lot longer so most roofing companies can install it correctly. Secondly the maintenance issue. No matter which system you have installed on your flat roof, if you properly maintain it, it’s going to last up to or beyond the warranty period. 



We’re not saying that single-ply roofing systems are bad and you shouldn’t consider them we’re only saying after thirty years in the commercial roofing industry and dealing with flat roofs, we prefer Modified Bitumen. Specifically, we prefer Modified Bitumen with the added protection of a cool roof silicone coating application on the roof.

This combination of durability, flexibility and cool roof savings makes it the best commercial roofing system on the market. Just look how long modified bitumen has been going and it’s still going strong despite the new single-ply systems that have come after it. 

As long as you find a commercial roofer that can install the system correctly, we’re confident in saying that in choosing a modified bitumen commercial roofing system you picked a great system that is going to give you many, many years of life. 




Skip to content