spray foam over granulated modified bitumen

Cost-Effective Repair for Modified Bitumen Roof

Greg PalyaSpray Polyurethane Foam Roofing

What should you do if you have a granulated modified bitumen roof and it’s leaking?

You might think the only option is to rip it all off and install a new system.

What if you could get a new roof installed for 1/3 of the cost of installing a new granulated roof?

That’s exactly what happened to Mercer County Career Center.

In this article, we’ll explain:

  • What a granulated modified roof is?
  • What repair options (and cost) do you have?
  • Why does spray foam make sense in this situation?

At the end of the article, we’ll share some before and after photos of spray foam installed over a granulated modified roof.

Let’s begin!

What is a granulated modified roof?

A granulated modified roof is a form of asphalt that’s rolled onto a roof in sheets. Torch down and cold applied with adhesive is the common installation method.

“Modified” is when extra materials are installed over the asphalt sheets. The purpose of the modification is to make the roof watertight.

Modified roofs come in smooth or granulated.

Granulated roofs have “granules” embedded into the roof membrane. Roofing companies mostly use white granules to add some UV reflectivity.

Here’s a photo of a 20+ year-old granulated modified roof:

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Now that you know if you have a granulated modified roof, what repair options do you have?

What repair options (and cost) do you have?

Option 1: Do a complete tear-off and install a new roofing system

Option 2: Install a roofing system OVER your current roof

Option 1: Do a complete tear-off and install a new roofing system

This will always be an option for anyone who currently has a granulated modified roof. The price is going to be costly, probably north of $20 per square foot.

This is because a complete tear-off requires extensive time and labor. Plus the costs of transporting the materials to a landfill.

One positive is that you can choose what the new roofing system will be. Popular choices today are single-ply’s and spray polyurethane foam.

But if cost-effectiveness is important to you, you should try to minimize the amount of tear-off.

Option 2: Install a roofing system over your existing roof

If you only have one roofing system installed, you can install a new one right over top.

Now, you’ll need to identify and remove all the saturated areas of the roof before the new install, but this is a great way to reduce costs.

Think about it, you might only need to remove a small percentage of your modified roof instead of 100% if you choose to perform a complete tear-off.

Now…If you already have two or more roofing systems installed, you’ll need to remove at least one system before a new one can be installed per building code.

But the whole point of this section is, why tear off a roof 100%, when you can only tear off the damaged and wet areas?

The best roofing system to install over a granulated modified is a spray polyurethane foam roof…and we’ll get into that below.

Why does spray polyurethane foam make sense to repair a granulated modified bitumen roof?

The #1 reason is that you won’t need to perform a complete tear-off. I know we beat that up earlier, but basically, it will save you a TON of money.

And when I say a “TON of money”, the last proposal we sent in was 1/3 the cost of the alternative.

The alternative was a complete tear-off and the installation of a new granulated modified bitumen roof.

Spray foam also makes sense because it’s sprayed-applied, and therefore can fill in every crevice of the roof.

Granulated mod-bit roofs are rigid and unsmooth.

A spray-applied system that expands is capable of adhering to every micro-inch of the roof.

Spray foam will also make the existing roof seamless.

Since the seams of a roof expand and contract when the temperature changes, the most stress on a roofing system happens at the seams.

Spray foam also has the best R-value per inch of any roofing insulation/membrane combo out there. This will reduce your energy expenses moving forward.

For Mercer County Career Center, the R-value of their existing roof increased by 10. Think of all the energy savings this will create over the 20-year warranty period.

Now that we know why spray foam is the best repair option for a granulated modified roof, let’s look at some before and after photos of a recent spray foam OVER a granulated modified roof.

Before and after photos of spray foam over a granulated modified roof

before and after photos of spray foam over granulated modified bitumen roof

What’s your next step?

I know that spray foam is a new roofing system that most have never heard of before. If that’s you, no worries!

We’ve created the Cheat Sheet to Spray Foam Roofing. All you’ll need to do is provide an email address (not your name, not your phone number, etc.) and we’ll send it to you.

West Roofing Systems has been installing and maintaining spray foam roofing systems since 1979.

If you have any questions, please contact us at any time.

The spray foam roofing cheat sheet - download now
About the Author

Greg Palya

Greg Palya is the Digital Content Manager of West Roofing Systems, Inc. He has a B.S. in Marketing from the University of Akron and an MBA in Marketing from Walsh University. When he's not trying to teach others about spray foam roofing and silicone roof coatings, you can find him on the basketball court or golf course.