What Is Roof Flashing?

Roof flashing is a thin sheet of metal—typically aluminum, copper, or galvanized steel—that’s installed in critical areas of your roof. Its job is to direct water away from seams, joints, and penetrations where leaks are most likely to occur. Flashing is essential in areas like:

• • Where walls and roof surfaces meet

• • Roof valleys

• • Around skylights and vents

• • Around chimneys

• • Along roof edges

Without flashing, water can seep under your shingles, damaging your underlayment, insulation, and even your home’s structure.

Why Is Roof Flashing Necessary?

Your roof is covered with asphalt shingles or other materials to keep out rain and weather. But shingles alone can’t do the job. Roof flashing provides an extra layer of protection that helps prevent leaks and water damage in the most vulnerable parts of your roof.

Types of Roof Flashing

Common Roof Flashing Types

• • Continuous flashing: Protects where a sloped roof meets a vertical wall.

• • Drip edge flashing: Installed along eaves to keep water flowing off the roof.

• • Step flashing: Overlapping pieces that protect wall-to-roof intersections.

• • Valley flashing: W-shaped flashing for roof valleys.

• • Vent pipe flashing: Cone-shaped flashing that seals around vent pipes.

Additional Roof Flashing Types

• • Base flashing: Fits around chimneys to direct water away.

• • Counter flashing: Works with base flashing for added protection.

• • Cap flashing: L-shaped flashing used on windows or flat surfaces.

• • Chimney flashing: Prevents water pooling around chimneys.

• • Saddle flashing: Covers protruding roof structures.

• • Skylight flashing: Protects skylight edges from leaks.

• • Kick-out flashing: Bridges gaps between step flashing and gutters.

What Is Counter Flashing?

Counter flashing works with base flashing to keep water from getting behind the flashing system. It’s typically installed on walls or chimneys to ensure water is directed away from the roof structure.

What Is Drip Edge Flashing?

Drip edge flashing is installed along the edges of the roof. It helps water run off the roof without soaking into the underlying materials or fascia, preventing rot and water damage.

Does Flashing Go Over or Under Shingles?

The placement of flashing depends on the roof area:

• • Under shingles in areas like valleys and lower roof edges.

• • Over shingles around chimneys, vents, or walls to direct water away.

Proper placement is essential to keep water from getting behind your shingles.

Aluminum vs. Galvanized Steel Flashing

• • Aluminum flashing: Lightweight, corrosion-resistant, easy to install, and long-lasting.

• • Galvanized steel flashing: More affordable but prone to rusting over time if not properly maintained.

Is Roof Flashing Required by Building Codes?

Building codes vary by location. Check with your local building department for specific requirements. However, most roofing manufacturers require flashing to be installed to maintain your warranty coverage.

How Long Does Roof Flashing Last?

Properly installed and maintained flashing can last 20–30 years or more. Regular roof inspections help identify early signs of wear or damage, allowing for timely repairs.

Common Roof Flashing Mistakes to Avoid

• • Improper installation or placement

• • Skipping flashing altogether in critical areas

• • Using the wrong material for your climate

• • Failing to seal joints properly

These mistakes can lead to leaks, mold, and costly repairs.

Why Professional Roof Flashing Installation Matters

Working with a qualified roofing contractor ensures:

• • Proper flashing type selection

• • Accurate installation for leak protection

• • Manufacturer warranty compliance

• • Long-term durability

Signs You Need Roof Flashing Repair or Replacement

• • Water stains on ceilings or walls

• • Visible gaps, rust, or damage on flashing

• • Leaks during or after storms

• • Missing or lifted flashing sections

Get Roof Flashing Repair & Installation in Oley, PA

At Mast Roofing & Construction, we specialize in roof flashing installation and repair for homes in Oley, PA, and surrounding areas. Our team ensures your roof is fully protected from leaks and water damage. Call (610) 689-3737 or book your inspection online to schedule your free consultation today.