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Deciphering Roofing Choices: Modified Bitumen vs. TPO Explained

December , 2023 | 10 min. read

By David Toth

I’ll be honest, repairing a flat roof can be tricky. I know what you’re thinking: that’s not something you want to hear a roofing contractor say, but it’s true! Tricky however doesn’t equal impossible in this scenario, especially when it comes to Modified Bitumen and TPO roofing. It will mean that during your project, your contractor should be providing your roof with a little more tender loving care than usual. 

Modbit and TPO roofs are flat but have unique water drainage challenges. Locating the origin of a leak on a flat roof can be complex. It requires expert detection skills. RoofCrafters takes pride in refining Modbit and TPO roof repairs. Our techniques are reliable and precise after almost 30 years. Our aim is to give property owners knowledge and understanding. We want you to be empowered when it comes to your roofing options.

Whether you're a Modbit or TPO roof owner, or simply seeking insights into these materials, this article is your go-to guide. We will explore Modbit and TPO roofing, including their pros and cons. Consider these factors when selecting the best material for your new roof. So let's dive in and explore these roofing options, equipping you with the knowledge to make better-informed decisions.

Getting to Know Modified Bitumen Roofing


Modified Bitumen, or Modbit for short, is a popular roofing material used for big buildings like stores and offices. It has been around for about 50 years. A mod bit is special because it's made of several layers. These layers include bitumen (which is a lot like asphalt), fiberglass, and rubber. When these layers are put together, they make a strong single-layer roofing system that is easy to put on and stands up well to weather.

What Does Modbit Look Like and How Is It Installed?


Modbit usually comes in rolls that are 3 feet wide. This makes it easy for roofers to roll it out and put it on the roof. The most common way to install Modbit is by heating it with a torch. This melts the bottom of the roll so it sticks to the roof.

torching mod-bit flat roof roll

This method is called "torch-down roofing." The other ways to put Modbit on the roof are self adhered, hot mop, and cold process. Yet, we see most installers using the torch-applied method.


Making Sure the Roof Is Waterproof


When putting on a Modbit roof, it's important to make sure all the edges of the rolls stick together tightly. This stops water from getting in. After the Modbit is all laid out and stuck together, the roofers add a final layer. This layer can be rough like sand or smooth. It helps protect the roof from the sun's rays.

roofer inspecting a failing mod-bit roof

In short, Modified Bitumen is a strong and long-lasting choice for low-slope roofing. It's liked by roofers because it's not too hard to install and does a great job of keeping the property safe from different kinds of weather.


Evaluating the Advantages and Disadvantages of Modified Bitumen Roofing


Modbit, or Modified Bitumen roofing, is a popular choice for low-slope roofs. It offers many benefits. This type of roofing is dependable. It has many benefits that make it perfect for flat roofs.

Advantages of Modified Bitumen Roofing:

  1. Environmental Friendliness: Modbit is known for being eco-friendly. It can often be recycled at the end of its lifespan, reducing environmental waste.
  2. Durability: One of the standout qualities of Modbit is its durability. It holds up well against various weather conditions, from intense sun to heavy rain, making it a long-lasting roofing solution.
  3. Versatility: Modbit is versatile and can be used on different types of buildings and roof designs. This adaptability makes it a practical choice for a wide range of commercial properties.
  4. Easy Installation: Installing Modbit is generally straightforward. Its ease of installation can mean quicker project completion times and potentially lower labor costs.
  5. Simple Repairs: If damage does occur, Modbit roofs are relatively easy to repair. This ease of maintenance can be a significant advantage for commercial property owners.

mod-bit flat roof over a porch

Disadvantages of Modified Bitumen Roofing:

But, like any roofing material, Modbit also has some disadvantages that should be considered:

  1. Sensitivity to Heat: During installation, Modbit requires heating, which can pose safety risks if not handled correctly.
  2. Aging: Modbit can become less flexible and more prone to cracking, especially under extreme temperature changes.
  3. Installation Weather Restrictions: The installation process for Modbit can be weather-dependent. Wet or very cold conditions can hinder the effectiveness of the installation.
  4. Aesthetic Limitations: Modbit may not offer as many aesthetic options as some other roofing materials, which could be a consideration for some property designs.
  5. Potential for Puncture: Though durable, Modbit can be susceptible to punctures from sharp objects, requiring careful maintenance and inspection.

In summary, Modified Bitumen roofing offers many benefits for low-slope roofs. Yet it's important to weigh these against the potential drawbacks to determine if it's the right choice for your property.

What is TPO Roofing and Why Choose It?


TPO stands for Thermoplastic Polyolefin(you see why the roofing industry shortened that?), it's shorter and easier to remember. Plus we all love acronyms, right? TPO roofing is a type of covering for roofs that were first installed on big buildings like grocery stores and offices. Shopping centers and big box stores like Home Depot, Lowes, and Best Buy all have TPO roofs.

Large TPO roof with skylights

Often considered a commercial roof system. But, sometime between 2005 and 2010, it began to be much more popular to install on residential houses. We attribute this to the ease of installation and cost.

Why is TPO Roofing Popular?

  1. Great at Keeping Buildings Cool: TPO roofing is usually white, and this color is really good at reflecting sunlight instead of soaking it up. This means that it can help keep your building or house cooler, especially during hot weather. This is a big reason why many people like TPO for their roofs.
  2. Easy to Maintain: TPO especially because it's a single-ply roof, can be maintained with ease. This means you can add on or do repairs without the headaches of more complicated systems.

roofer welding seam on a TPO roof with a hand welder

In simple terms, TPO roofing is a popular choice for both big buildings and homes because it helps keep them cool. It's important to take good care of it, like cleaning it often, to make sure it stays effective.

Pros and Cons of TPO for Low-Slope Roofs


Just as with Modbit, commercial and residential property owners with low-sloped roofs have found it helpful for protecting their investments. TPO roofing has its own advantages and disadvantages.  It's important to understand both before making a final decision.

They include:


  • Energy Efficiency
  • Flexibility and Durability
  • Easy Maintenance
  • Simple Repairs
  • Less Labor Intensive

TPO roof on a home with a skylight


  • Limited Color Options
  • Sensitivity to Certain Chemicals
  • Potential for Shrinkage Over Time
  • Relatively Newer in the Market
  • Requires Professional Installation for Optimal Performance

We feel it's important that you understand the maintenance that may be needed before making your decision.  This way you have an idea of what's involved to properly maintain the roof system. 

Comparing Modified Bitumen and TPO Roofing: Which Suits You Best?


Now that we’ve discussed what these two roofing systems are all about, let’s get into the comparison. Both of these roof systems are a great choice for any commercial or residential property with a flat roof. So, you may be asking. "Which one is the best for you?"

Take these key points into consideration.


Key Considerations for Modified Bitumen Roofing


  1. An excellent choice for moisture protection, however, most require additional drainage systems to work effectively.
  2. The positive results and efficiency of a new Modbit roof are undeniable, but the materials cost more and are more labor-intensive to install.
  3. Modbit has been around for over 50 years and is an incredibly trustworthy option, although some believe this option is becoming outdated while new technologies continue to develop.
  4. While Modified Bitumen is environmentally friendly in the sense that it can be recycled once it's no longer in use if petroleum and other chemicals are used during the manufacturing process, the “green” aspect of depleted.
  5. In most cases, it comes with less warranty. The average warranty is 10-12 years for Modbit.

Evaluating TPO Roofing for Your Property Needs


  1. While TPO is less expensive than Modbit upfront and costs less to install as well, it does not have the same long-lasting durability. Meaning it's not as tough as Modbit. It can puncture easier than a Modbit roof.
  2. Unlike Modified Bitumen, TPO roofing systems can handle heavy amounts of water remaining on the roof. Which can help tremendously if the roof has less slope. 
  3. TPO is relatively new on the market, but don’t let that scare you. In recent years, it has come to be one of the most in-demand products in the roofing industry.
  4. Efficient and effective in their construction, TPO is one of the most functional commercial roofing options available. 
  5. TPO has longer-lasting warranties available. The average material warranties are 15-20 years with some TPO manufacturers offering a 30-year material warranty. 

Making the Right Roofing Choice: Modified Bitumen vs. TPO


Choosing between Modified Bitumen (Modbit) and TPO roofing for your business isn't about finding a clear winner. Both options have their unique strengths and are excellent choices for commercial roofing. To find the perfect match for your building, consider its unique requirements. These include design, size, location, and personal preferences.

Guidance in Making Your Decision:

To navigate this decision, it's wise to involve a professional roofing contractor. An expert can inspect your roof and provide personalized advice. They will compare the advantages of Modbit and TPO based on your building's specific needs. They can guide you in choosing the material that will serve you most effectively.

Finding the Right Contractor:

If you're unsure where to start in finding a skilled contractor, RoofCrafters is here to help. We encourage you to download our checklist, “The Top 10 Questions You Want to Ask Your Potential Roofing Contractor.”

image call to action, download the top 10 checklist

RoofCrafters is skilled in Modified Bitumen and TPO roofing. We provide excellent warranties and reliable service. Don’t delay in securing the best for your business. Schedule an inspection with our experienced estimators today. In the meantime, our learning center is full of resources to help you become better educated to make the best decisions for your investment.

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David Toth

My name is David Toth and I am the lead estimator in North Florida with RoofCrafters Roofing. Originally from New Brunswick, I have called Florida home for the past 47 years. I enjoy cooking along with traveling to different historical areas in Florida when I have free time.