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What is Roof Flashing?

What Is Roof Flashing?

Roof flashing is a thin sheet of metal installed on a roof to direct water away from joints, seams, and other weak spots. It creates a watertight barrier that prevents leaks, protecting your home’s interior from costly water damage. Without properly installed flashing, even a new roof can fail prematurely and when flashing fails due to corrosion or poor installation, timely roof repair becomes vital to safeguard your home.

Why Roof Flashing Matters

How Flashing Prevents Leaks

Every roof has vulnerable areas where two surfaces meet or where something protrudes, such as chimneys or vents. Flashing ensures water is channeled safely off the roof and into the gutters instead of seeping inside.

Risks of Damaged or Missing Flashing

If flashing is cracked, rusted, or missing, leaks are almost inevitable. Over time, this can cause rot, mold growth, and even structural damage. Routine roof inspections can help spot these issues early.

Common Roof Flashing Materials

Different metals are commonly used for flashing, each with advantages:

  • Aluminum – Affordable, lightweight, and flexible, though it needs coating to resist corrosion.

  • Copper – Attractive, extremely durable, and long-lasting, but more expensive.

  • Stainless Steel – Resistant to rust and strong, ideal for long-term protection.

  • Galvanized Steel – A budget-friendly choice that balances durability and cost.

 

Where Roof Flashing Is Installed

Roof flashing is strategically placed anywhere water naturally flows or collects:

  • Roof Valleys – Where two roof slopes meet.

  • Chimneys, Vents, and Skylights – Around roof penetrations that need extra sealing.

  • Dormers and Roof Perimeters – At intersections and edges where leaks often begin.

  • Eaves and Fascia Boards – Directs water into gutters and away from the home.

Flashing is particularly important in areas where different roof elements meet like chimney bases or dormers. For example, homeowners that schedule roof maintenance in Fircrest inspect and replace worn or corroded flashing before leaks begin. Catching flashing issues early can save you a lot in downstream damage.

 

Signs You Need New Roof Flashing

Watch for these warning signs:

  • Water Leaks – Stains on ceilings or walls are a clear indicator.

  • Rust and Corrosion – Deteriorating flashing can’t protect against water.

  • Rotting Wood – Moisture-damaged framing around chimneys or vents.

 

How Long Does Roof Flashing Last?

Most flashing lasts as long as the roof itself—about 20 to 30 years. However, storms, poor installation, or lack of maintenance can shorten its lifespan. That’s why it’s smart to have a roof inspection every few years. To protect the investments of homeowners, roof flashing should be replaced whenever evidence of direct water entry or corrosion of previously installed flashing is detected. Failure to act under such circumstances can result in areas of your roof needing to be replaced. 

In extreme cases, chronic leaks can cause structural damage to joists, beams and internal walls. Roof replacement may even be necessary.

 

Professional Installation vs DIY Flashing

Installing flashing correctly requires precision. A misaligned or improperly sealed piece can cause leaks rather than prevent them. While small patch jobs may seem DIY-friendly, hiring a roofing contractor ensures long-term protection and warranty coverage.

When installed by expert roofing contractors, the lifespan of flashing is between 15 and 20 years. Ensuring the integrity of your roof surface represents an important aspect of ongoing property maintenance and home improvement.

The skills and knowledge of a professional roofer are particularly important when navigating various roof slopes, chimney flashing, vent pipe flashing, kickout flashing, apron flashing and other roof features that may be unique to your home. 

For example, step flashing is rectangular and bent 90 degrees in the center. It is used for roof to wall flashing and installed in layers with shingles to ensure water flows away from walls.

Another type of flashing are drip edges. These are L-shaped pieces of metal flashing that divert water away from fascia boards and into rain gutters.

Depending on the roofing material, base flashing can be installed a few different ways. For example, when the roof meets the wall of a dormer, underlayment is run up the side of the wall for a few inches. Then the roof covering is installed.

With composite asphalt shingles, the flashing is installed on top, with another layer of shingles sometimes added for aesthetics. 

These practices create several layers of protection at the most vulnerable parts of a roof. Counter flashing, which may also be used for extra protection, is when pieces of flashing are installed vertically over base flashing, but continues a few more inches up the wall.

Different types of flashing are used on different areas of the roof. Depending on the roofing material, base flashing can be installed in several ways. For instance, when a roof meets the wall of a dormer, underlayment is run up the side of the wall for a few inches. 

When composite asphalt shingles are used, the flashing is installed on top, then sometimes another layer of shingle tabs may be installed for aesthetic reasons. 

 

Protect Your Home With Proper Roof Flashing

Because roofing needs can differ greatly from one home to another, the advice of professional roofers is all the more important. If flashing fails, water can seep into the attic, insulation, or walls. For real-world examples of this happening, see our blog post What Caused My Puget Sound Roof to Leak? It shows how small flashing failures or leaks around roof features often lead to serious damage when not addressed promptly.

If you are concerned about your roof flashing, or suspect that your roof may leaking, contact ACME Roofing today for a consultation and free estimate. 

ACME Roofing provides the highest quality roofing services in the South Sound Region. We take pride in delivering the best roofing services. Our local roofers are highly trained and experienced and offer the reliable services you can depend on for a strong and sturdy roofing system.

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