TPO vs. Modified Bitumen: Which to Choose?

TPO vs. Modified Bitumen: Which to Choose?

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If you have just built a new home or commercial building, and you are looking to install a roof, there are many good options at your disposal. However, having so many options can make things confusing. For instance, two very commonly used roofing materials include TPO and modified bitumen.

However, these two are fairly different from each other, both of which have their advantages and disadvantages. Today, we’re going to do a side-by-side comparison of both to figure out which one is best used for your next project.

What Is TPO Roofing?

First, we have TPO roofing, which stands for thermoplastic polyolefin. This is one of the most popular roofing systems that can be found across the world. What is important to note however is that the name is very misleading. This is because the roofing materials used here are not actually made out of plastic, but rubber. Specifically, a combination of polypropylene and ethylene-propylene rubber is used.

The two are attached to each other to form a single sheet. This single layer of synthetic roofing material, combined with a reinforcing scrim, is used to cover a variety of flat and semi-flat roofs.

This is generally reserved for commercial building applications. What is interesting is that TPO was designed as a better solution to PVC roofing and other alternatives, although whether or not it is better than bitumen roofing is questionable at best.

A huge advantage that you get with TPO roofing is that the cost is usually quite low, lower than with most other types of roofing. Furthermore, this material is white on top, which is beneficial for energy purposes, as it reflects some light away from the building in question.

This helps reduce cooling costs in the summertime. Another big advantage of TPO roofing is that it can be attached to a roof deck with adhesives or it can be attached directly with fasteners.

Furthermore, it can also be heat welded, which makes it easier to get around chimneys. Many people also like TPO roofing because it is fairly resistant to corrosion and breaking down due to contact with a variety of chemicals.

It is also fairly resistant to mildew and algae growth. One of the only real issues with TPO roofing is that it is so new that it doesn’t have the best track record yet, and moreover, it generally doesn’t last more than about 10 years.

What Is Modified Bitumen Roofing?

We then have modified bitumen roofing, which is often considered to be one of the best roofing materials in the world. This method of roofing is characterized by the use of many layers of roofing materials.

These many layers consist of asphalt, polymerized rubber, plastic, and fiberglass to create a flexible yet rugged waterproof membrane that is extremely impact-resistant and resistant to virtually all forms of damage.

Modified bitumen itself consists of hot asphalt, rubber, and plastic. Here, rolls of material are placed in between layers of felt, which are then coated with modified bitumen, and these are known as cap sheets or polymer layers.

Depending on the exact material used here, which can differ from one application to another, these modified bitumen roofing membranes can be installed as a part of a multi-ply system or a two-layer system.

This should therefore be able to cover up the exterior surface of any roof, although it is usually used for semi-flat and flat roofs, specifically for commercial purposes, and has been in use for over 100 years.

Modified bitumen roofing is extremely durable, strong, and long-lasting, but also difficult to install. It’s very dangerous to do, it’s difficult, and there are multiple layers, plus it’s time-consuming, so professional installation is absolutely required. Although some places might still charge a lot for this type of roof, the costs have come down significantly over the years.

TPO Roofing vs. Modified Bitumen Roofing: What Are the Differences?

Now that we know what both TPO and modified bitumen are, let’s take a closer look at what makes these two types of roofing applications different.

Overall Durability

What is interesting to note is that TPO roofing is very durable, but modified bitumen roofing may be even more so. Because TPO is most often made with a single layer of polypropylene rubber, it is quite durable and resistant to impact, tearing, and other forms of damage.

However, modified bitumen roofing is made with rubber, plastic, felt, asphalt, and more, of which there are multiple layers. This means that modified bitumen roofs generally tend to have more impact and tear resistance.

Flat roofs made with bitumen are usually much more durable in terms of foot traffic as well. They handle being walked over much better than TPO roofs.

In general, you can expect a well-installed TPO roof to last for around 10 years, whereas a modified bitumen roof can last anywhere from 15 years up to 30 years or more.

UV Resistance

In terms of UV resistance, due to the color of the materials and the materials themselves, TPO roofs handle sunlight better than modified bitumen. Modified bitumen roofs, especially if not properly installed and treated, may start to suffer from UV damage over time, which may include cracking, warping, and other forms of damage.

Heating and Cooling Costs

What many people like about TPO roofing is that the top layer is white. This automatically helps reflect away a lot of sunlight, therefore reducing cooling costs in the summer. On the other hand, modified bitumen roofing tends to be black or dark on the exterior, so it absorbs sunlight.

Although this is not beneficial for cooling costs in the summer, it can be beneficial for heating costs in the winter. Therefore, TPO would appear to be better for lowering cooling costs whereas modified bitumen would appear to be better for lowering heating costs.

Maintenance and Water Damage

One of the big advantages that you get with a TPO roof is that it is easy to spot damage and irregularities. This means that you should be able to easily see cracks on the surface. This is opposed to modified bitumen roofing, which often has gravel spread over the top, resulting in limited visibility.

With modified bitumen roofs, it’s hard to see damage, cracks, and water pooling up. In the long run, this means that you might not spot damage, particularly water damage, which can then lead to much greater issues over the long run.


In general, TPO roofing is much easier to install. You can use fasteners to screw the TPO layer down to the roof, or you can use adhesives. Technically speaking, this is something that somebody could do even if they were not a total professional.

However, with modified bitumen roofing, you most certainly require professional installation, because you’re working with multiple layers of rubber, plastic, felt, burning hot asphalt, and hot blow torches as well.

This is something that requires professional installation, which can be somewhat costly. Furthermore, keep in mind that during the installation process for modified bitumen, fire torches are used, and it is not uncommon for buildings to suffer from fire damage, or even very rarely to burn down due to improper installation practices.


The other thing to consider here is that modified bitumen roofs usually cost no more than $4 or $5 per square foot, whereas TPO roofs may cost up to $14 or even $15 per square foot.

TPO Roofing vs. Modified Bitumen Roofing: Which One Should You Use?

As you can see, both types of roofing have their advantages and disadvantages. If you are going for long-term durability, and you want something cheap, then modified bitumen roofing is the way to go.

However, TPO roofing does much better in hot summer conditions, both because it reflects light and because it is very resistant to UV rays. Furthermore, TPO roofs are also much easier to install and less time-consuming. They also require less maintenance, and make it easier to see if there is damage.


As the years go on, TPO roofing is becoming more popular, but modified bitumen roofing is still prevalent as well.