Flashing Roofing

by S&K Construction And Remodeling | Aug 28, 2025 | Blog

Flashing Roofing: A Complete Guide for Homeowners

When homeowners ask about flashing roofing, they are seeking to understand one of the most critical components of a roof system. Flashing is the material used to seal and protect areas of a roof that are vulnerable to water penetration, such as around chimneys, vents, skylights, and roof valleys. Proper installation and maintenance of flashing are essential to prevent leaks and extend the life of a roof.

This comprehensive guide will cover the purpose of roofing flashing, types of materials, installation methods, common problems, maintenance tips, and considerations for repair or replacement. By the end, homeowners will have a clear understanding of how flashing roofing works and why it is crucial for a durable, leak-free roof.

What Is Flashing Roofing?

Flashing roofing refers to thin pieces of material, usually metal, installed to direct water away from critical areas of a roof. Flashing prevents water from seeping into the roof deck, insulation, and interior of the home.

Key Functions of Flashing Roofing

Water Diversion: Channels water away from roof intersections, joints, and penetrations.
Leak Prevention: Seals areas where shingles, roof decking, or other materials meet.
Structural Protection: Protects the roof deck and underlying structure from water damage.
Durability Enhancement: Extends the lifespan of roofing materials by preventing moisture-related damage.

Without properly installed flashing, even the best shingles or roofing materials can fail due to water infiltration.

Common Areas Where Flashing Is Used

Flashing is installed in several critical areas of a roof:

1. Roof Valleys

Flashing is often installed beneath shingles in roof valleys to direct water off the roof.
It prevents water accumulation in these high-traffic runoff areas.

2. Chimneys

Step flashing and counter flashing are installed around chimney bases to seal gaps.
Flashing prevents leaks where the masonry meets the roof surface.

3. Skylights

Flashing surrounds skylights to ensure a watertight seal.
Properly installed flashing prevents leaks during heavy rain or snow.

4. Roof Vents and Pipes

Pipe collars or vent flashing protect plumbing and ventilation penetrations.
They seal gaps where the pipes pass through the roof decking.

5. Dormers and Roof Intersections

Flashing seals intersections of different roof planes or dormer walls.
It prevents water from penetrating seams or joints.

Types of Flashing Roofing Materials

Flashing can be made from a variety of materials depending on the roof type, climate, and budget:

1. Aluminum

Lightweight and easy to shape.
Resistant to rust and corrosion.
Suitable for most residential roofs.

2. Galvanized Steel

Strong and durable.
Requires protective coating to prevent rust.
Common for valleys, chimneys, and roof edges.

3. Copper

Extremely durable and long-lasting.
Resistant to corrosion and weathering.
Often used in high-end or historic homes.

4. Lead

Soft, malleable, and durable.
Often used in complex roof designs or chimneys.
Can be expensive and requires skilled installation.

5. Rubber or Synthetic Flashing

Flexible and easy to install.
Used around plumbing vents or roof penetrations.
Resistant to cracking and weathering in extreme temperatures.

Types of Flashing Roofing

Different roofing applications require specific types of flashing:

1. Step Flashing

Installed in layers with each course of shingles along vertical surfaces like walls or chimneys.
Provides a step pattern that diverts water away from the roof.

2. Continuous or Base Flashing

Long, continuous strips installed along the base of walls or roof intersections.
Often combined with counter flashing to provide extra protection.

3. Counter Flashing

Installed over base or step flashing.
Protects the underlying flashing from water penetration and weather exposure.

4. Valley Flashing

Installed along roof valleys to guide water off the roof.
Can be open, closed, or woven depending on roof design.

5. Drip Edge Flashing

Installed along roof edges to direct water into gutters.
Protects fascia and roof deck from water damage.

6. Vent and Pipe Flashing

Seals around plumbing vents, exhaust fans, and other roof penetrations.
Typically pre-formed to fit standard pipe diameters.

Installation of Flashing Roofing

Proper installation is essential for flashing to perform its function:

1. Roof Preparation

Inspect roof decking for damage or rot before installing flashing.
Clean the surface to ensure proper adhesion of materials.

2. Cutting and Shaping

Metal flashing is cut to size using tin snips or metal shears.
Flexible materials are shaped to fit the roof contours and penetrations.

3. Placement

Step flashing is installed with each shingle course along walls or chimneys.
Valley flashing is placed in valleys before shingles are installed.
Drip edges are installed along roof edges prior to shingles.

4. Securing Flashing

Nails or screws are used to fasten metal flashing.
Sealants may be applied to create a watertight barrier where necessary.
Counter flashing is installed over base flashing to protect against water infiltration.

Common Problems With Flashing Roofing

Even properly installed flashing may encounter issues over time:

1. Rust and Corrosion

Metal flashing exposed to moisture can rust if not coated or maintained.
Copper and aluminum are less prone to corrosion than steel.

2. Loose or Damaged Flashing

Wind, ice, or physical damage can loosen flashing.
Loose flashing allows water to seep beneath shingles.

3. Cracked or Missing Sealant

Sealants around roof penetrations can crack over time.
Gaps in sealant can lead to leaks and water damage.

4. Improper Installation

Incorrect placement or alignment can compromise water diversion.
Valleys, step flashing, and counter flashing require precise installation to prevent leaks.

5. Debris Buildup

Leaves, branches, and other debris can accumulate around flashing areas.
Debris can trap moisture, accelerating wear or causing leaks.

Maintenance of Flashing Roofing

Regular maintenance is key to prolonging the life of flashing:

Inspect Flashing Annually: Check for rust, cracks, or loose pieces.
Clean Debris: Remove leaves and dirt to prevent water accumulation.
Check Sealants: Reapply or replace cracked or missing sealant.
Address Damage Promptly: Repair or replace damaged flashing to prevent leaks.
Professional Inspection: Have a roofing contractor inspect flashing during roof maintenance or replacement.

Signs of Flashing Roofing Problems

Homeowners should watch for signs that flashing may need repair:

Water stains on ceilings or walls near roof penetrations.
Visible rust, cracks, or separation in metal flashing.
Missing or bent flashing pieces along roof edges or valleys.
Shingle damage around roof penetrations.
Mold or mildew growth in the attic due to leaks.

Addressing these issues promptly prevents extensive water damage and costly repairs.

Repair and Replacement of Flashing Roofing

When flashing is damaged or improperly installed, repair or replacement is necessary:

1. Step Flashing Replacement

Remove damaged shingles along the wall or chimney.
Install new flashing in layers with shingles.
Ensure proper overlap to direct water away from the roof.

2. Valley Flashing Repair

Remove damaged or corroded flashing.
Replace with properly sized and positioned metal flashing.
Ensure shingles are correctly aligned to prevent leaks.

3. Drip Edge Replacement

Remove old drip edge along roof edges.
Install new drip edge before replacing shingles.
Seal corners and overlaps to prevent water infiltration.

4. Sealant Renewal

Remove old, cracked sealant from penetrations.
Apply high-quality roofing sealant to create a watertight barrier.

Choosing the Right Flashing Material

When replacing or installing flashing, consider:

Climate: Corrosion-resistant metals like aluminum or copper for wet or coastal regions.
Roof Type: Certain flashing materials work better with asphalt, metal, or tile roofs.
Budget: Aluminum or galvanized steel is cost-effective, while copper is premium.
Longevity: Copper flashing can last decades, while aluminum and steel may require maintenance.