When homeowners ask, “What is flashing on a roof?” they’re often dealing with a leak—or trying to prevent one. Roof flashing is one of the most critical (and most overlooked) parts of your roofing system. It’s designed to protect the most vulnerable areas of your roof from water intrusion, including chimneys, vents, skylights, and intersections between roof slopes.
In this post, we’ll explain what flashing on a roof is, why it’s so important, the different types of roof flashing, and how to know when it needs repair or replacement.
What Is Flashing on a Roof?
Roof flashing is a thin material—typically aluminum, galvanized steel, copper, or rubber membrane—installed around areas of the roof that are especially prone to leaks. These include places where the roof meets walls, dormers, chimneys, and vent pipes. Flashing directs water away from these joints and toward the gutters.
So if you’re wondering what is flashing on a roof, the answer is simple: it’s a barrier that keeps water out where shingles alone aren’t enough.
Why Roof Flashing Is So Important
Without properly installed roof flashing, even the best shingles can’t prevent water from finding its way in. Leaks caused by missing or damaged flashing are some of the most common reasons homeowners call us.
Here’s why flashing on a roof matters:
- Prevents water leaks at roof intersections and penetrations
- Extends roof lifespan by reducing moisture damage
- Protects roof decking and interior insulation from rot and mold
- Improves overall performance of your roofing system
Types of Roof Flashing
When asking what is flashing on a roof, it’s helpful to know there are several different types, each serving a specific purpose:
- Step Flashing: Used where a sloped roof meets a vertical wall (like around dormers). Installed in overlapping pieces.
- Continuous Flashing (Apron Flashing): A single long piece of flashing used where a roof meets a vertical surface.
- Counter Flashing: Installed over step flashing, usually on chimneys or masonry.
- Valley Flashing: Sits in open roof valleys to channel water downward.
- Vent Pipe Flashing: Custom-fit pieces designed to seal around pipes that come through your roof.
- Drip Edge Flashing: Installed along the roof’s edge to protect decking and guide water into gutters.
Each type of flashing on a roof has a critical role in keeping your home dry.
How to Know If Your Roof Flashing Is Failing
Roof flashing doesn’t last forever. And when it fails, the damage can be costly. Here are some signs to watch for:
- Visible rust, corrosion, or gaps in flashing
- Water stains on ceilings or attic walls
- Mold or mildew around roof penetrations
- Curling shingles near chimneys or vents
- Flashing that’s lifted, bent, or missing entirely
If you’re unsure whether your home has roof flashing damage, our team at BCM Roofing offers professional inspections to assess your roof’s condition.
When to Replace or Repair Roof Flashing
If flashing is loose, rusted, or damaged, repairs may be possible—but in many cases, it’s smarter to replace it altogether. For example:
- If your roof flashing is part of an older roofing system
- If you’re replacing the roof and want to start fresh
- If flashing is improperly installed or poorly sealed
One of the most common causes of recurring roof leaks is failing to replace flashing when installing new shingles. Don’t let that happen to you. If you’re in Southeast Michigan and wondering what is flashing on a roof and whether yours is in good shape, give BCM Roofing a call. We’ll give you an honest assessment.
Get Help From Michigan’s Trusted Roofing Team
If you’re wondering what is flashing on a roof or suspect that yours may need repair, don’t wait for the next big storm to find out. BCM Roofing has helped hundreds of Michigan homeowners protect their homes with reliable, high-quality flashing and leak prevention.
We know the local weather—and we know how to build roofs that last. Whether you need a small repair or a complete roofing system replacement, our team is here to help.
Schedule your free inspection today and let us help you protect your home from the top down.
FAQs About Roof Flashing
What is flashing on a roof made of?
Roof flashing is usually made from aluminum, galvanized steel, copper, or rubber. The material is chosen based on your roofing type and climate.
Can you replace flashing without replacing the whole roof?
Yes—if flashing is the only issue, it can often be replaced or repaired independently. However, if you’re already replacing your roof, it’s smart to install new flashing at the same time.
Is roof flashing required?
Yes. Building codes generally require flashing around chimneys, vent pipes, walls, and roof valleys. It’s a critical part of a watertight roofing system.
How long does flashing on a roof last?
Depending on the material and installation, flashing can last 15–30 years. Regular inspections help catch wear and tear early.
How much does it cost to replace flashing on a roof?
It depends on the type and location of the flashing. Minor repairs may cost a few hundred dollars, while full replacements (especially around chimneys or valleys) can be more.
