Modified Bitumen Roofing: What Homeowners Need to Know About Granule Cap Sealing

If you've got a modified bitumen roof—or you're considering one—there’s one crucial detail that often gets overlooked: granule cap sealing.

At The Roof Champion of Columbus, we’ve seen firsthand how something this small can make a big difference in how long your flat or low-slope roof lasts. Let’s break it down simply so you can make the best decision for your home.

What Is Granule Cap Sealing?

Modified bitumen membranes often come with a top layer embedded with granules, similar to what you see on asphalt shingles. These granules protect the membrane from UV rays and weathering.

But during installation, especially around seams, overlaps, flashings, and repairs, those granules can get scraped off or disturbed. That’s where granule cap sealing comes in.

It’s a simple two-step process:

• A thin, even layer of roofing mastic is applied over exposed or disrupted areas.

• Granules are pressed into that mastic to match the surrounding surface.

Why It Matters for Your Roof

When the granules are missing, that underlying membrane is exposed to sun, rain, snow, and ice. Over time, that weakens the material and leads to early failure.

Here’s why granule sealing matters:

• UV Protection – Prevents accelerated aging of the asphalt.

• Water Resistance – Reduces the risk of ponding, blistering, or micro-cracks.

• Warranty Compliance – Many manufacturers require this step to maintain coverage.

• Visual Consistency – Helps avoid patchy, uneven roof surfaces.

When Should It Be Done?

Our team typically seals granule caps during:

• New roof installation

• Sealing base flashings

• Repairing damaged sections

• Installing roof penetrations (vents, drains, etc.)

• Touch-ups after snow guard or HVAC work

If you’ve had work done on your flat or low-slope roof and didn’t see your contractor adding granules back in—it’s worth checking.

Real Example from Columbus

We recently helped a homeowner in Dublin whose modified bitumen roof was only five years old but showing signs of premature wear at the seams. Turns out, the original installer skipped granule sealing. We cleaned, mastic-sealed, and re-granulated all critical areas—and extended that roof’s life by years.

Our Promise: No Shortcuts. Ever.

At The Roof Champion, we don’t just install a roof—we install it to last. That means paying attention to the details, like cap sealing, because cutting corners always costs more later.

If you’re in Columbus, Powell, Westerville, or anywhere nearby and you’ve got questions about your flat roof, give us a call. We’ll take a look—no pressure, no sales pitch. Just honest feedback from someone who knows what they’re looking at.

FAQs

How do I know if my roof needs granule sealing?
Look for bare black patches on your modified bitumen roof—especially at seams, corners, or flashings. Or call us for a quick inspection.

Is granule sealing needed on every modified bitumen roof?
Yes, in some areas—especially where granules have been scuffed or where sealant was used. It’s part of proper installation and repair.

Can I do it myself?
Not recommended. Applying the wrong mastic or using poor-quality granules can cause adhesion failure or void warranties.

Contact Us Today
📍 177 Chasely Circle, Powell, Ohio 43065
📞 (614) 639-3422
🌐 www.roofchampcolumbus.com