Modified Bitumen Roofing Flashings with Bitumen: Real Protection for Your Flat Roof

If your home or garage in Columbus has a low-slope or flat roof, chances are modified bitumen is one of the best roofing options for you. It’s tough, time-tested, and—when installed properly—can keep your structure watertight for decades.

But one of the most overlooked and misunderstood aspects of modified bitumen systems is the flashing work, especially when it’s applied using hot bitumen. And bad flashing is often where leaks start.

Let’s walk through what you really need to know.

What Is Modified Bitumen Roofing?

Modified bitumen (MB) is a multi-layer roofing system made from asphalt and rubber modifiers. It’s designed for low-slope or flat roofs and is applied in one of three main ways:

• Hot-applied with bitumen (torch-down or mop-down)

• Cold-applied with adhesives

• Self-adhering (peel-and-stick)

When we’re talking about flashing with hot bitumen, we’re usually working with the hot-applied method.

Why Flashing Matters—Especially in Columbus

Flashing is used to seal areas where the roofing material meets vertical surfaces or penetrations like:

• Chimneys

• Skylights

• HVAC curbs

• Walls and parapets

If flashings are poorly done or skipped entirely, water finds its way in—especially during Columbus's freeze-thaw cycles, wind-driven rain, and heavy spring downpours.

Flashing Installation: The Right Way

When using hot-applied bitumen, the flashings are installed with a layered approach that bonds tightly to the base membrane. Here's what proper installation looks like:

1. Clean and Prime the Surface:
   All surfaces must be clean and primed before installing base plies or flashing plies.

2. Apply Base Ply and Membrane Plies:
   We extend membrane plies vertically up the wall at least 8 inches, fully adhered with hot asphalt.

3. Install Cant Strip at Vertical Transitions:
   A 45-degree cant strip helps ease the transition between horizontal and vertical surfaces, preventing cracking.

4. Embed Flashing Plies in Hot Bitumen:
   Flashing sheets are embedded directly into hot asphalt to create a tight seal. The top layer is usually a granulated cap sheet or surfacing layer.

5. Seal Termination Points:
   We finish with metal termination bars, counterflashing, and sometimes sealant to complete the system.

At The Roof Champion of Columbus, we follow ARMA and NRCA guidelines to the letter—because anything less leads to failures.

Real Talk: Common Issues We Fix

Too often, we’re called to repair someone else’s poor flashing job. Some issues we see:

• No cant strips, causing membrane cracks at transitions

• Cold joints from improperly applied bitumen

• Loose or missing metal edge flashing

• Water trapped behind poorly installed wall flashing

These aren’t small mistakes—they’re the kind of problems that lead to soaked insulation, mold, and deck rot.

Why You Need a Specialist for Modified Bitumen Flashing

This isn’t DIY. And it’s not something just any roofer with a caulk gun and torch should be touching.

Hot-bitumen work requires:

• Trained installers

• High-quality ASTM-rated materials

• Precise temperature control

• Attention to Columbus’s climate-specific expansion and contraction

Travis Haessly, owner of The Roof Champion, has personally trained our crew on these techniques. We don’t just slap on tar and hope for the best—we build for the long haul.

Serving Homeowners Across Columbus & Beyond

We specialize in flat and low-slope roofs in:

• Columbus

• Powell

• Worthington

• Dublin

• Hilliard

• Westerville

• Grove City

• New Albany

• Plain City

• Upper Arlington

• Gahanna

• Delaware

If you’ve got an older flat roof or are dealing with leaks near walls or pipes—call us before the damage gets worse.

FAQs

How long should modified bitumen flashings last?
Properly installed flashings using hot bitumen can last 20+ years. The key is correct installation and regular inspections.

Can I coat over bad flashing?
No. Coatings can’t fix bad detail work. You need to remove and reinstall flashing properly.

What kind of maintenance does this system need?
Annual inspections and after major storms. Look for cracks, uplifted edges, and punctures—especially around transitions and penetrations.

Ready for Real Protection?

Call The Roof Champion of Columbus at (614) 639-3422 or visit us online to schedule a roof inspection.

We don’t quit. We fight. We win.