TPO vs. Modified Bitumen Roofing System (Cost, Lifespan, Etc.)

Modified Bitumen vs TPO

TPO vs. Modified bitumen is a common debate for many commercial building owners.

TPO Roof Coating

Key Takeaway

TPO is clearly better than modified bitumen because of its energy efficiency, longevity, reliability, customization, and versatility. As a result, TPO roofs are also more expensive.

Generally speaking, two kinds of commercial flat roofing systems are most commonly found in the Northeast. These are modified bitumen and thermoplastic polyolefin or TPO. The former has been around since the 1970s and is one of the more traditional methods of flat commercial roofing.

TPO has been around since the 1990s, and both do well in extreme temperatures, both extremely hot and bitterly cold. And given the locale (the northeast), this is a perfect set of traits to have to stand up to the huge swings in temperature.

More and more these days, however, TPO commercial roofing is surging in popularity. You might not have realized that TPO roofs are installed more than all other flat roof alternatives combined, including a PVC flat roof.

This piece will take a deeper look into both kinds of roof systems and examine each of them. This includes cost, expected life and longevity, and overall value of each roofing system so that you can make the most informed decision possible.

Modified Bitumen Flat Roofs

One of the primary benefits of using a modified bitumen roof is that it comes at a lower installation cost. However, one of the biggest disadvantages is that many major commercial roofing contractors have stopped installing them, mostly due to the surge in popularity of TPO roofs. Some have gone as far as to start installing TPO over modified bitumen.

As stated previously, modified bitumen began back in the 1970s and became a major upgrade over the traditional asphalt roofs of the time. It is termed “modified” because of the addition of substances like styrene butadiene styrene (SBS) or atactic polypropylene (APP), which were intended to enhance both flexibility and longevity of the roof, especially when compared to those old asphalt roofs.

Over the years, several issues have arisen when it comes to modified bitumen roofs. The first is that, although an APP-modified bitumen roof is designed to resist things like UV-light damage, cracking, blistering, and oxidation, there has been a lack of standards in the industry which has led to manufacturers skimping on the addition of that APP as a modifier.

What is the downside of that, exactly? This causes the roof to underperform. When the roof underperforms, that can lead to costly repairs. In the worst case, it could mean that your commercial roof needs replacing, adding another costly endeavor to your plate.

The second issue with modified bitumen flat roofs is that, although the gravel spread over a modified bitumen roof is intended to offer hazard and UV protection, that granular surface makes it more difficult to correct drainage issues and detect leaks.

Those drainage issues and leaks can persist far longer than they might with a TPO roof, which means that there can be a buildup of water that can damage the roof’s structure. When something like this happens, it can create structural integrity issues that can lead to even more costly repairs to your commercial business than you had ever expected.

The third issue with modified bitumen flat roofs is that using an open flame torch during installation can be a fire hazard. There have been more than a few instances of buildings burning when a torch used in the installation process was mishandled.

Roofer Fixing Modified Bitumen Material

The risk here is definitely substantial, and it can be substantial enough that some insurers won’t even cover roofers who apply modified bitumen while using the open torch method. That is why open torch installations of modified bitumen are becoming a rarer commodity. With that said, the modified bitumen roof cost remains appealing to some.

Thermoplastic Polyolefin (TPO) Flat Roofs

This method is also known as flexible thermoplastic polyolefin (FTPO) roofing. Generally speaking, there are three different kinds of commercial roof installations involving TPO: ballasted, fully adhered, and mechanically fastened.

TPO is considered one of the best values in commercial roofing because it offers several different advantages. And when it comes to your commercial roof, getting valuable and longevity are definitely two of the most important aspects involved.

The tear-resistant single-ply membrane is tough and resists oil, grease, and chemical spills. Not only that, but TPO roof systems are also fully recyclable and UV-resistant. Best of all, TPO single-ply roofing is often considered a “green” option because no plasticizers are included in the formulation process.

One of the cool aspects of the rise of TPO roofs in commercial roofing installations is that many building owners and managers now have the option of selecting from over a dozen different colors. This includes white, which has proven to have energy-saving abilities to it as well.

The great thing about this is that now you can match your new roof to the exterior color of your building. This might not seem like much, but matching that color scheme can make your building stand out in the eyes of passersby.

Best of all, some of those initial costs of installing an Energy Star-rated TPO roof can be potentially recovered through lower energy costs over the life of that commercial roof. That makes it easier to take on the initial costs of installing the TPO roof to your commercial building.

Additionally, it is possible to apply TPO roofing systems over top of pre-existing modified bitumen and metal roofs. This is as long as the current roof is in sound condition and not substantially worn or damaged. Applying the new roofing system over the top of an existing roofing system eliminates additional tear-off costs and will reduce the overall disposal expenses. That is a win-win across the board.

TPO is a reheatable and weldable material as well. This means that it is possible to re-weld any seams that require it years later. On top of that, smooth-surfaced TPO roof systems are easier to maintain and clean than those granular-surfaced roofs, like a modified bitumen offers. Cleaning and maintaining your roof properly means that the roof will hold up for longer, saving you from having to get a new roof for a long time to come.

The thickness of the standard TPO single-ply membranes can vary a bit. Some are around 40 mils but can be as big as 800 mils. If your roof is in an area where punctures are more likely – due to falling large branches or other sharp objects – you might want to look into a thicker membrane to ensure that your roof does not get punctured by any of those falling objects.

The installation here is key, as is the case with any type of commercial roofing system. Whenever a TPO roof fails, this is often the result of damage that is done during the installation process. If it isn’t, it is because seams were not properly welded during the installation process.

These seam failures can lead to leaks or potential catastrophic failures when extreme winds occur, causing wind uplift. While these are certainly worst-case scenarios, they are things to be aware of when installing a TPO roof. When you hire a skilled, experienced roofing contractor to handle the installation process, you generally don’t have to worry about these worst-case TPO scenarios.

TPO Roofing Material

The better manufacturers in the TPO roofing system business consistently produce high-quality, longer-lasting TPO membranes that you can have confidence in and get a longer life out of than ever before. Again, proper installation methods from a certified commercial roofing contractor will ensure that the TPO roof is installed properly and likely won’t fail.

Final Call: Modified Bitumen vs. TPO (TPO is King)

Despite being cheaper, there are just too many downsides to using a modified bitumen roof to make it a viable option anymore. TPO is more energy-efficient, more reliable, and more versatile than its counterparts in the roofing industry.

Combined with the ability to customize the color of your roofing surface, there is just no matching TPO as a commercial roofing option. They also last longer than bitumen flat roofs, meaning you save on the costs of a potential installation that would occur sooner rather than later with a bitumen roofing system.

When you run a commercial business, there are a million things you need to keep in mind and worry about; your commercial roof should be at the very bottom of that list. When installing a TPO flat roof on your building, you properly protect it from even the most extreme of elements for a long time.

You can save a ton on installation costs over the years when your heating and cooling bills are far less than ever. You can have confidence in your commercial roof to stand the test of time and handle the elements easily, allowing you to focus on the most important aspects of your business, like generating revenue to keep that business going.

TPO is the reigning king of roofing materials and will likely hold that spot for a long time to come.