Torch down roofing is called modified bitumen roofing, or mod-bit for short. It’s a type of flat roof system that uses a special material that gets heated with a torch during installation. The torch melts the tar-like substance so it bonds to the roof. This method has been popular for decades. It works well for commercial and residential flat roofs. Many contractors still use it today because it’s durable and reliable.
What Is Modified Bitumen Made of?
Modified bitumen is made from asphalt mixed with polymers. These polymers make the material more flexible and strong. The base layer is often fiberglass or polyester. A thick tar-like coating covers the top.
The top layer is usually dark gray or black. This helps keep heat away from your attic. According to RubyHome (2025), modified bitumen roofing falls in the flat roofing category with costs ranging from $5.50 to $7.50 per square foot for installation included.
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How Does the Torch Installation Work?
A roofer uses a propane torch to heat the bottom of the roofing material. The heat melts the tar, creating a sticky bond. The roofer then rolls the material flat onto the roof deck.
This process takes skill and practice. One mistake can cause problems later. According to the U.S. Bureau of Labor Statistics (May 2023), roofers earn a median wage of $24.05 per hour, and this specialized work requires proper training and experience.
How Long Does Modified Bitumen Last?
Modified bitumen roofs typically last 20 to 30 years. With good care, some last even longer. According to industry data provided by RubyHome (2025), modified bitumen has a lifespan of 20 years on average. This is shorter than metal roofing, which lasts 40 to 80 years.
Regular maintenance helps extend the roof’s life. You should have it inspected at least once a year. According to IBISWorld (2025), the U.S. roofing contractor industry reached $81.3 billion in market size, with approximately 80% of roofing activity now focused on renovation and replacement work.
Torch Down Vs. Other Flat Roofing Options
There are other ways to install flat roofs. Some don’t use torches at all. Here’s how they compare:
| Roofing Type | Installation Method | Lifespan |
|---|---|---|
| Modified Bitumen | Torch down (heated) | 20-30 years |
| Built-Up Roofing | Multiple layers | 15-30 years |
| TPO/EPDM | Glued or mechanically fastened | 15-20 years |
According to ConsumerAffairs (2024), single-ply roofing systems dominate commercial work, with 91% of commercial roofers using TPO (38%), EPDM (30%), or PVC (18%) instead of torch-down methods. Each option has pros and cons. Torch down is reliable but requires skilled labor. Other methods may be faster or cheaper. Talk to a local roofer about what works best for your roof.
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Talk with a local professional roofer to review your options and get a detailed estimate for your project.