How to Install Roof Flashing Against a Wall

Posted on January 31, 2025

Estimated Reading Time : 5 Min.

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How to Install Roof Flashing Against a Wall

An essential part of any roofing system, roof flashing works as a barrier to keep water out and shield the underlying structure. Roof to wall flashing may be necessary around parts such as the chimney or around dormer windows. Installing flashing against a wall can be a little challenging, but with the correct equipment and methods, it can be an easy process. When done properly, it guarantees a tight, waterproof seal that will shield your house and roof for many years to come.

In this blog post, we will walk you through the process of installing roof flashing against a wall, answering a simple question every homeowner has: How do you install roof flashing against a wall?

What Is Flashing On A Roof?

Flashing On A Roof

A crucial part of any roofing system is the flashing. It prevents water from entering areas like dormers, chimneys, skylights, roof valleys, and more. Made from materials such as copper, aluminum, or galvanized steel, it acts as a barrier to direct rainwater away from these vulnerable spots. This ensures water flows into the gutters instead of seeping into your home. 

  • Waterproofing: Redirects water away from vulnerable areas to stop leaks
  • Durability: Built from strong materials like galvanized steel or copper to resist harsh weather 
  • Versatility: Comes in various types, such as step, apron, and counter flashing, for different uses
  • Prevents Structural Damage: Shields the roof from water damage that could weaken its structure
  • Ease of Installation: Easy to install, providing a professional fit to ensure a tight, secure seal

Also Read: Understanding the Different Types of Drip Edge Flashing

How to Install Roof Flashing Against a Wall

Now that we know what roof flashing is, let’s delve in to get a better understanding of how to install roof flashing against a wall. Let’s break down each step:

Tools and Materials Needed

Here are some tools and materials you’ll need to get started:

TOOLSMATERIALS
Measuring tapeBase flashing
Tin snips or hacksawStep flashing
Cordless drillCounter flashing
Roofing nails or screwsRoofing sealant
Caulking gunWeather-resistant barrier (optional)
Chisel or Masonry BitKickout Flashing

Step 1: Prepare the Area

Proper preparation is the first step toward a successful installation:

> Clear the Work Area

Begin by removing any existing shingles or debris from the area where the flashing will be installed. Clean away dirt or old sealant to ensure proper adhesion. A clean surface enhances how well the materials will bond.

> Inspect for Damage

Carefully examine the roof deck and wall for signs of damage or rot. Repair any compromised areas before proceeding in order to prevent future problems.

> Safety First

Wear appropriate safety gear, including gloves and non-slip footwear. If working on a steep roof, use fall equipment that prevents falls such as harnesses to minimize risks.

Step 2:  Install Base Flashing

Laying down base flashing provides the first layer of defense against water infiltration at the roof-wall connection:

> Cut Base Flashing to Size

Measure and cut a continuous piece extending at least 6 inches up the wall.

> Position Base Flashing:

Place it along the bottom edge where the roof meets the wall, ensuring at least a 2-inch overlap onto the roof deck.

> Secure Base Flashing:

Nail along every 12 inches down its length, avoiding edges to prevent punctures.

> Seal the Edges:

Apply roofing cement along all edges for a watertight seal.

Step 3: Install Kickout Flashing

The next step is to install the kickout flashing which plays a vital role in directing water away from the wall and into the gutters, preventing potential moisture damage.

> Cut and Fit Kickout Flashing:

Ensure it fits snugly in the roof-wall corner and trim it if necessary.

> Position Kickout Flashing:

Place it at the lowest edge of the roof-wall intersection, overlapping the base flashing.

> Secure the Flashing:

Nail the upper portion in place to prevent leaks.

> Seal the Edges:

Use roofing cement to create a watertight seal.

Step 4: Install Step Flashing

Adding step flashing in an overlapping pattern ensures water flows properly away from the roof-wall junction:

> Position the First Piece:

Place the first piece of step flashing above the kickout flashing, ensuring proper alignment.

> Nail the Flashing:

Secure the flashing with two nails on the upper portion.

> Install Shingles:

Lay the first shingle course over the step flashing, leaving a small portion exposed.

> Continue Overlapping:

Install subsequent pieces of step flashing, ensuring at least a 2-inch overlap with the previous one.

Step 5: Install Counter Flashing

Covering the exposed edges of the base flashing with counter flashing further provides extra protection against leaks:

> Prepare the Wall:

If installing on masonry, cut a 1-inch deep groove using a chisel or masonry bit.

> Cut Counter Flashing:

Measure and trim counter flashing pieces to fit into the grooves.

> Insert Counter Flashing:

Fit each piece into the groove and overlap it with base flashing.

> Secure and Seal:

Fasten using masonry screws or nails and apply roofing cement along the edges.

Step 6: Final Sealing and Inspection

Once all flashing is in place, a final inspection ensures proper alignment and water resistance.

> Seal All Joints

Apply roofing cement or sealant along joints and overlapping areas.

> Inspect the Installation

Check for gaps, misalignment, or exposed edges that may lead to leaks.

> Reinstall Siding

If the siding was removed, reinstall it carefully, allowing space for proper drainage.

Common Mistakes to Avoid When Installing Roof Flashing Against a Wall

Let’s go over some common mistakes to avoid for a successful flashing installation:

1. Using Incorrect Materials

Use the right flashing material for your roof to prevent issues like corrosion that can weaken the structure over time

2. Inadequate Sealing

Seal all joints and edges properly to prevent water leaks and mold growth, which can cause long-term damage.

3. Improper Flashing Placement

Ensure flashing is placed correctly to direct water away from vulnerable areas and avoid pooling, leaks, and rot.

4. Not Considering Expansion and Contraction

Flashing must be able to handle temperature changes in order to prevent shifting and leaks.

5. Ignoring Signs of Damage

Regularly inspect for rust, cracks, or loose flashing to catch and fix problems early before they worsen.

6. Insufficient Overlap

Ensure flashing pieces overlap sufficiently to allow proper drainage and prevent leaks.

Maintenance and Longevity Tips

Once installed, you want to make sure that your flashing lasts. To ensure protection, here are some maintenance tips to keep your flashing roof in top shape:

1. Regular Inspections

Check flashing every six months for rust, cracks, or loose fasteners.

2. Clear Debris

Remove leaves and twigs to prevent moisture buildup and corrosion.

3. Trim Overhanging Branches

Cut back branches to reduce debris and damage risks.

4. Use Gentle Cleaning

Clean with a soft brush or low-pressure hose to avoid damage.

5. Maintain Insulation

Ensure attic insulation prevents moisture buildup that can harm flashing.

6. Prompt Repairs

Address damage immediately by resealing or replacing flashing that has become damaged.

7. Professional Help

Hire a contractor for expert inspections and maintenance if needed.

Protect Your Roof with Professional Roofing Services from OConnor Contracting

Installing roof flashing against a wall is essential for preventing water damage. By carefully measuring, cutting, and sealing, you can protect your home from leaks and ensure long-lasting protection. Taking these steps will help protect your roof from potential issues down the line.
Professional roof flashing installation is essential to protect your home from water damage. If you’re not confident installing it yourself, OConnor Contracting is here to help. Our expertise in flashing and roofing services ensures your roof is secure and watertight, preventing expensive leaks and repairs down the road. Trust us and give us a call at (716) 600-7663 today.

How to Install Roof Flashing Against a Wall