What Is Torchdown Roofing? Pros, Cons, and Costs

Are you looking for a material that will protect your roof from leaks and water damage but aren’t sure if torchdown roofing is right for you? Have you been struggling to find a flat roof material that resists cracking, UV damage, and general wear and tear over time?

At RoofSmart, we understand that choosing the right roofing material can be difficult, especially when it comes to flat or shallow-slope roofs. To help our customers choose roofing materials, we take them through our SmartMatch Needs Analysis process. This matches them with several options that best meet their needs, preferences, and budget.

We believe that it’s important to understand the potential pros and cons of each roofing material (as well as other key information) before making your final decision. So, we wrote this article to help you learn more about torch down.

In this article, you’ll learn about:

• The types of torchdown
• How torchdown is installed
• The pros and cons of torchdown
• How to know when torchdown is the right fit for you

By the end, you’ll be able to make an informed decision about whether torchdown is the right material for your roof’s needs and your budget.

What are the different types of torchdown?

There are two main types of torchdown : APP and SBS. You’ll get similar protection from each one, but there are some differences:

APP

APP (Atactic Polypropylene) torch down is the classic torchdown that is applied to the roof using a blowtorch. It is made of asphalt but has plastic properties that make it UV-resistant and durable .

It’s not very difficult to install, but you do have to make sure that it stays at the right temperature to stick onto the roof. You cannot let it overheat or underheat. It also can’t be too cold out while you’re installing it.

And, of course, using a blowtorch does always pose a potential risk of setting fire to your home (an experienced professional shouldn’t have any issues, but sometimes accidents happen).

SBS

SBS (Styrene-Butadiene-Styrene) torchdown is pretty similar to APP. Both are made with asphalt, but SBS is more flexible and has better impact resistance .

This can be applied using a blow torch, but it’s designed to be a peel-and-stick application . However, if it’s raining or the roof is at all wet, the installation will not work. However, it can be installed in colder weather.

How is torchdown installed?

Torchdown is installed on the roof by using a blowtorch to melt it and ‘weld’ it onto the roof. However, the process looks a little different depending on how many layers of material are used.

Single-Ply With No Base Sheet (AKA Torchdown Done Wrong)

This is just a singular sheet of torch down made of modified bitumen that gets installed on the roof. Typically, single-ply torchdown is used in situations where your budget is tight or you have a temporary need.

Single-ply torch down is less durable and won’t last as long as other styles.

Single-Ply

With single-ply torchdown, a fireproof base sheet is first nailed down onto the roof. This acts as a fire shield to protect the roof while the cap sheet layer gets torched on .

Having only one layer provides the least amount of protection and durability, but it is the most common due to its relatively affordable cost. This has a life expectancy of 10-15 years depending on the environment. However, things such as pooling water or excessive tree debris can shorten the lifespan.

2-Ply

2-ply torchdown has a mid-ply that is smooth, with no granules, and then an additional layer on top that has granules (the cap sheet) . This provides added protection against UV rays and enhances the roof’s durability.

Two-ply torchdown is best for extreme weather conditions and can last the longest , which is typically around 20-25 years.

What are the pros and cons of using torchdown on the roof?

In order to decide if torchdown is right for you, it’s important to weigh the pros and cons. That way, you understand the full picture.

Pros:

• Low cost: One of the more affordable flat roofing material options at $7 to $9 per square foot.
• Low maintenance: The only thing you need to worry about with torchdown is clearing off debris (like leaves or pine needles). Other than that, it doesn’t require much upkeep.
• Safer and more durable walking surface: Just like asphalt shingles, torchdown has a granulated layer on top. This makes the surface grippy even when it is wet, creating a much safer surface to walk on while you’re doing maintenance. It is also more resistant to scuffing or damage from being walked on than other flat roof materials.
• UV resistance: The granulated layer on top helps to protect the torchdown material from harmful UV rays that would otherwise cause it to deteriorate. APP-modified bitumen has excellent UV resistance.

Cons:

• Risk of fire during installation: Torchdown is melted and sealed onto the roof using a blowtorch. Experienced professionals know how to handle this equipment, but sometimes accidents happen.
• Leaks: When installed properly, torchdown offers good water protection. But if it’s not sealed well or the sealing around the scuppers fails after a while, this can lead to leaks and water damage in your roof.
• Short lifespan: Torchdown typically lasts 12 to 15 years, which is less than the other flat roof materials.

When is torchdown the right fit for me?

You might be wondering how you know when torchdown is the best choice for your roof. Here are some scenarios that can help you decide :

• You have a flat or low-slope roof: These roof types require certain roofing materials to prevent leaks. Torchdown provides good waterproofing, making it ideal for commercial buildings, apartment complexes, and homes with flat or low-slope roofs.
• You’re worried about your roof cracking when the temperature changes: Torchdown can expand and contract as the temperature changes. Luckily, it is flexible and won’t crack or break as the seasons change. SBS-modified bitumen is the most flexible in fluctuating climates.
• You want a roof material that blends with asphalt shingles: Does your roof have some areas with a regular slope and some areas that are low slope or flat? Do you already have asphalt shingles but want better protection in vulnerable areas without ruining your roof’s curb appeal? If so, torchdown is a good option because it looks similar to asphalt shingles, but it will be better for keeping water out.

Need a roofer to install your flat roof, but don’t know how to find one that’s reliable and experienced? Use our Qualified Roofer Checklist!

Is torchdown roofing the right fit for your home?

After learning about torchdown roofing, you now have a clearer understanding of its types, installation process, pros, and cons.

If you have a flat or low-slope roof and need a durable, waterproof solution, torchdown could be a great fit—especially if you’re looking for a material that expands and contracts without cracking. However, if fire risks during installation or a shorter lifespan are concerns, you may want to explore alternative options.

Wondering what other roofing materials you can use on your flat or shallow slope roof? Check out our article “4 Types of Flat Roofs: Pros, Cons, and Costs” to learn about your other options and compare costs.