If you spent any time near construction or renovation sites, there’s a chance you witnessed torches or open flames on rooftops. Although this may seem like an odd sight, it’s actually common to use torches for roof installation. This torch down roofing is an energy-efficient solution that’s been used to install membranes on flat commercial roofs for decades.

Officially known as modified bitumen, torch-down roofing is a rolled roofing (find out everything about rolled roofing) product consisting of a nonwoven polyester mat and a membrane embedded in a thick asphalt layer. The material is strong, durable, and weighs less than 2 pounds per square foot, making it an efficient material for roofing.

Manufacturers sell this roofing material in two different styles: smooth and granulated. Granulated sheets come in different colors that reflect the sun’s rays, keeping your home cooler and reducing your energy bills. Smooth sheets are less expensive and often used as a cost-effective under-layer for new roofing. If you pick granulated sheets, you must tear them off when it’s time for a replacement roof.

Torch down roofs have multiple benefits, but they’re not for everyone. Read on for more information about roofing materials, costs, and the potential pros and cons of choosing a torch down roof.


How Much Does Torch Down Roofing Cost?

Torch down roofs are usually more expensive than asphalt roofing, though final costs depend on the components and contractor. Historically, they were cheaper than hot tar roofing, but liability insurance for roofers working over open flames has driven up costs in recent years. However, torch down roofing could still save you money by minimizing repairs.

Torch down costs an average of $4 to $8 per square foot installed, excluding deck repairs. A 1,500-square-foot roof would cost between $6,000 and $12,000 for materials and professional installation. Granulated cap sheets tend to cost a little more than smooth, so adding them may increase your final cost.

For comparison, read our article that outlines how much a flat roof costs.


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How Is Torch Down Roofing Installed?

Torch down sheets get heated by a torch as they’re rolled out on the roof, creating a seamless, impermeable layer. The installation process inspired the name of the technique, which stuck.

Here is an overview of torch down roofing installation steps:

  • If needed, tear off existing roof material.
  • Inspect the roof deck and make needed repairs.
  • Install insulation like polyiso boards (optional).
  • Heat and press down the base sheet.
  • Roll out the granulated top sheet and fuse seams with a torch.
  • Apply a reflective coating after one or two months.

The additional reflective coating is added protection, which installers apply several months later after initial installation. The extra layer reflects sunlight and heat, yielding more durability. You can choose a single- or dual-ply system, but according to Gotcha Covered Contracting, single-ply is more common.

You must use proper torching techniques to get an even seal between roofing plies. Don’t attempt without practicing.

Today’s Homeowner Tips

When using a torch, have safety precautions, such as fire extinguishers, on hand. Monitor sparks to avoid accidents.


Why Choose Torch Down Roofing?

Benefits that make torch down a wise option compared to other flat roofing materials include:

The asphalt layer of torch down roofing contains rubber additives that allow for expansion and contraction during temperature changes. This flexibility makes a torch down perfect for flat or low slope roofs on your home. Likewise, the seams are also more flexible than those of single-ply roofing membranes.

With options for multiple thicker plies, torch down roofing better resists punctures from falling objects versus single-ply membranes. This added durability can protect your roof better in natural disasters and accidents.

With torch down roofing, dark-colored surfaces heat up in sunlight to vaporize condensation moisture before it can cause rot and damage to your roof’s underside. This can eliminate the threat of mold and mildew.

Torch down roofing is highly water-resistant and durable for 20+ years with minimal repairs, comparable to the roof lifespan of other materials like PVC and TPO. This long service life can save you money. Be sure to factor in how long a roof lasts when choosing the material for your roof.

Torch down roofing has fiberglass and asphalt construction that provides inherent fire resistance. Building codes even require torch down for some commercial projects, though residential applications are more common.


Maintaining Torch Down Roofs

Taking care of your torch down roof is important for maximizing its lifespan. You’ll need to routinely inspect, clean, and repair it over the years.

To maximize your roof lifespan, maintain it by:

  • Inspecting your roof two or three times a year and after major storms
  • Removing debris with a broom or leaf blower
  • Re-coating every three to five years
  • Patching holes, cracks, and lifted seams
  • Cleaning drains and gutters

Torch down needs less frequent recoating than built-up roofs, making it easier to maintain. With routine roof care, you can expect a 20+ year service life from your torch down roof. If you want to learn more about how to repair your roof, check out our step-by-step guide.


Comparing Torch Down to Other Flat Roofing

Torch down offers similar roof durability as the following popular single-ply options: PVC is lightweight, reflective, and offers heat-welded seams. However, it tends to be more expensive. TPO offers heat-weldable material, good chemical resistance, and vulnerable seams. EPDM is lightweight, seamless, flexible, and chemical-sensitive.

Torch down makes the most sense on decks that can’t adhere to single-ply membranes, and it can provide added benefits that these other materials don’t offer. However, if you’re trying to decide what material is right for your roof, the above options are all competitive choices.


Is Torch Down Roofing a Good Choice?

Used for decades on commercial flat roofs, torch down is a durable and reliable material with options for redundant plies and welded seams. It’s a smart choice for older roofs or roofs where adhered membranes won’t work.

While it’s very efficient and relatively inexpensive, torch down has some downsides too. Installation is labor intensive, requiring skilled roofers. On top of that, seams can fail if not properly heated during application. However, torch down remains a viable, cost-effective roofing system when installed correctly.


FAQs About Torch Down Roofing

How long do torch down roofs last?

With proper maintenance, you can expect torch down roofs to last up to 25 years or longer.


What is the slope requirement for torch down roofing?

You can install a torch down roof on roofs with up to a 3:12 slope, but the optimal slope is 1/2:12 or less.


Is torch down roofing waterproof?

Torch down roofs are waterproof. They have a water-tight membrane when installed on top of a sturdy roof deck.


Can you install a torch down roof over an existing roof?

Yes, but the old roof has to be prepared first. If you plan on installing over an existing roof, contact a professional. Many roofers counsel against putting a new roof over an old roof because it won’t last as long, but it saves time and money for homeowners.


Is torch down roofing fireproof?

Torch down roofing is fire-resistant but not fireproof.


Does torch down roofing contain asbestos?

No, modern versions use fiberglass mats instead of asbestos.


Editorial Contributors
avatar for Mitchell Layton

Mitchell Layton

Mitchell Layton is a former professional mover who currently lives in Philadelphia, Pennsylvania. Mitchell spent years packing and moving for REAL Rock N Roll Movers, a commercial and residential moving company based in Los Angeles that’s primarily staffed with up-and-coming musicians. That gave him plenty of experience navigating box trucks up and down the winding streets of LA. In addition to moving hundreds of happy customers into new homes and apartments all across Southern California, Mitchell has also performed corporate moves on company lots for Nickelodeon, Warner Bros, Universal Studios, Paramount, and more. After pouring blood, sweat, and tears into his profession, Mitchell has all the helpful tips you need for your next move.

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Sabrina Lopez

Editor

Sabrina Lopez is a senior editor for Today’s Homeowner with over 7 years of writing and editing experience in digital media. She has reviewed content across categories that matter to homeowners, including HVAC services, home renovations, lawn and garden care, products for the home, and insurance services. When she’s not reviewing articles to make sure they are helpful, accessible, and engaging for homeowners like herself, Sabrina enjoys spending time with her family and their two parrots.

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