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How to Install Flashing on Metal Roofs: Your Expert-Backed Guide

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how to install flashing on metal roofs

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Metal roofs are renowned for their durability and weather resistance, but their performance significantly depends on the right installation of critical components. 

One such component is flashing, a protective barrier designed to direct water away from the delicate parts of your roof. 

Unfortunately, many homeowners are left in a conundrum on how to install flashing on metal roofs. 

To install flashing on metal roofs, start by installing the sidewall trim. Then, cut and finish the end wall flashing, ensuring it aligns perfectly with the sidewall trim. Proceed with the foam closure installation, overlapping the end wall trim. Finally, fasten the end wall flashing for a secure and water-tight seal.

Incorrectly installed flashing can lead to severe water damage, while proper installation increases the lifespan of your roof and improves its overall weather resistance.

How to Install Flashing on Metal Roofs – Brief Guide

Flashing installation on metal roofs involves an intricate series of steps that ensure the longevity and functionality of your roof. 

First, you need to understand the different types of flashing and their roles in protecting different areas of your roof. 

Then, prepare your roof for installation by cleaning it, taking accurate measurements, and cutting the flashing pieces accordingly.

When installing the flashing, secure the base, attach the flashing, and seal the joints carefully. 

As for the step-by-step guide, start by installing the sidewall trim and cutting the end wall flashing. 

Follow this with foam closure installation and overlapping the end wall trim. The process concludes with fastening the end wall flashing securely, giving your roof the resilience it needs against the elements. 

While it may seem intricate, each step plays a pivotal role in ensuring the structural integrity of your roof.

Understanding Flashing: An Essential Component for Metal Roofs

Flashing is a type of thin material, usually galvanized steel, that professional roofers use to direct water away from critical areas of the roof, where it’s likely to collect or leak into the house. 

In other words, it’s a waterproofing system that protects your roof and home from water damage.

Types of Flashing

The world of roofing is home to a wide array of flashing types, each engineered for a specific role in safeguarding your roof. 

For those eager to fortify their metal roofs, it’s crucial to understand the various flashing types and their distinct characteristics.

  • Continuous Flashing: Often referred to as ‘long length flashing’, continuous flashing provides a long, unbroken piece of material installed to direct water away from locations where a vertical wall meets a side of the roof. It’s preferred over other types of flashing because it reduces the chances of water seeping through gaps.
  • Drip Edges: Drip edges are installed along the eaves and gable ends of the roof to prevent water from being drawn back by capillary action and damaging the underlying roof structure. This type of flashing is critical in guiding water off the edges without dripping directly onto the underlying fascia boards.
  • Step Flashing: This is designed for the intersection of the roof and wall. Each small section of the step flashing works together to guide water down the top and away from the walls. It’s called ‘step’ flashing due to the design resembling a staircase’s steps.
  • Valley Flashing: This W-shaped flashing is used in the roof valleys, a familiar spot for water accumulation. The design of valley flashing ensures that water is directed straight off the roof, preventing leaks.
  • Vent Pipe Flashing: This type of flashing is specifically designed to seal off the area around vent pipes, flues, exhaust pipes, and similar protrusions. It prevents water from infiltrating these vulnerable spots on the roof.

Choosing the correct type of flashing for your metal roof ensures comprehensive protection against various weather conditions. 

Each serves a unique purpose, and selecting the right one is vital to the durability of your roof.

Why Should You Install Flashing on Metal Roofs?

When it comes to safeguarding your home, installing flashing on metal roofs is more than just an option, it’s essential. This essentiality can be better comprehended by understanding the key benefits flashing brings to your roof:

  • Water Damage Prevention: The primary purpose of flashing is to keep water out. It ensures water is directed away from the critical areas of the roof, such as joints, seams, and roof features. This dramatically reduces the risk of moisture damage, leaks, and the resultant repair costs.
  • Increased Lifespan of Your Roof: Flashing provides an extra layer of protection against harsh weather, increasing the lifespan of your roof. It protects the roof’s integrity by shielding its most vulnerable parts from rain, snow, and ice.
  • Enhanced Aesthetic Appeal: While functionality is paramount, aesthetics matter too. A well-flashed roof not only safeguards your home but also enhances its visual appeal, boosting the overall curb appeal of your property.
  • Improved Weather Resistance: Flashing adds a layer of robustness to your metal roof, reinforcing its weather resistance. This means a flash roof can withstand these conditions better, whether it’s a storm, heavy rain, or harsh sun.
  • Cost Efficiency: While there might be an upfront cost involved in installing flashing, the long-term savings in maintenance and potential repair costs make it a worthwhile investment. An adequately flashed roof means minimal chances of water leaks and subsequent structural damage.

Perfecting the Craft: Mastering Roof Flashing Techniques

Installing flashing is a craft that requires precision and expertise. Whether you’re a DIY enthusiast or a professional roofer, mastering the techniques of flashing installation can go a long way in ensuring your roof stays in excellent condition for years.

Flashing Preparation Techniques

Preparing your roof for flashing installation is the first and arguably the most critical step. Here are some techniques that ensure a successful installation:

  • Roof Surface Cleaning: Prior to installation, thoroughly clean the roof surface to ensure it’s free from dust, debris, and any residual moisture. A clean surface promotes better adhesion of the flashing, providing an optimal base for installation.
  • Taking Precise Measurements: Accurate measurements are critical when preparing to install flashing. Measure the areas where flashing will be installed, such as around vents, edges, and junctions of different roofing sections. These measurements should guide the cutting of the flashing pieces to ensure a precise fit.
  • Cutting the Flashing: Utilize your measurements to cut your flashing accurately. Remember, it’s better to cut slightly larger than your measurements. Excess can be trimmed later, but inadequate flashing may result in leaks or damage.
  • Forming the Flashing: Some types of flashing may require forming or bending to fit specific roof features. Carefully shape the flashing using a brake or other bending tool to ensure a snug fit around corners or curves.

Flashing Installation Techniques

With preparation complete, you can move on to the installation process. Follow these techniques for an efficient and secure flashing installation:

  • Securing the Base: Start by securing the base flashing onto the roof. Use appropriate fasteners, typically roofing nails or screws, and ensure they are spaced correctly. This creates a solid foundation for the remaining installation.
  • Attaching the Flashing: Once the base is secured, attach the main flashing to the roof. Align the flashing correctly with the roof’s structure, ensuring no gaps or loose areas.
  • Sealing the Joints: To prevent any water leaks, it’s essential to seal all joints. Use a high-quality roofing sealant and apply it generously at the joints. Ensure it’s spread evenly for a tight seal.

Step-by-Step Guide to Install Flashing on Metal Roofs

With a firm understanding of the preparation and installation techniques, let’s delve into a detailed step-by-step guide to installing flashing on metal roofs:

1. Installing Sidewall Trim

Installing the sidewall trim provides the initial setup for the flashing installation. Here are the steps:

  • Measure the Area: Measure where the sidewall trim will be installed. Cut the trim according to the measurements, leaving some extra material for adjustments.
  • Align and Secure the Trim: Align the trim against the sidewall and roof surface. Secure it using roofing screws, ensuring it’s fastened tightly for a firm, watertight seal.

2. Cutting and Finishing the Endwall Flashing

This phase requires meticulous execution. Here’s how to go about it:

  • Measure and Cut: Measure the end wall area and cut the flashing slightly larger than the measured size.
  • Fold and Seal: Fold the excess material around the edges to achieve a smooth finish. Seal the folded edges firmly to prevent any water intrusion.

3. Foam Closure Installation

Foam closure installation is crucial to effectively seal the gaps between the metal roofing panels and flashing:

  • Place the Foam Closure: Place the foam closure strips under the lower lip of the flashing. This fills in the gaps, providing added insulation and protection against weather conditions.
  • Secure the Closure: Use adhesive or screws to secure the foam closure. Make sure it fits snugly and does not move around.

4. Overlapping Endwall Trim

Overlapping the end wall trim correctly maintains the integrity of your roof and prevents potential leaks:

  • Place the First Piece: Place the first piece of end wall trim on the roof, ensuring it’s aligned correctly with the roof’s edge.
  • Overlap the Pieces: Overlap subsequent pieces of end wall trim over the first, maintaining a consistent overlap distance for a seamless appearance and water flow.

5. Fastening the Endwall Flashing

The final step is fastening the end wall flashing securely in place:

  • Place the Screws: Place the screws at the top of the flashing, not through the face. This helps prevent water seepage.
  • Secure the Flashing: Tighten the screws until the flashing is firmly attached to the roof, but avoid over-tightening, which may deform the flashing or strip the screw holes.


Knowing how to install flashing on metal roofs is a critical skill every homeowner should possess. 

It saves you potential costs associated with water damage and increases your roof’s lifespan and overall performance.

From understanding the flashing types to mastering installation techniques, and finally, the detailed step-by-step guide, you are now equipped with the essential knowledge required for a successful flashing installation. 

So, go ahead and safeguard your metal roof against adverse weather conditions and ensure a healthy, leak-free home.


What types of flashing are best for metal roofs? 

For metal roofs, the most suitable types of flashing include continuous flashing, drip edges, step flashing, valley flashing, and vent pipe flashing. Each type serves a distinct purpose and provides protection to specific areas of your roof.

Why is it necessary to install flashing on metal roofs? 

Installing flashing on metal roofs is crucial to prevent water damage. It directs water away from roof joints and features, enhancing the lifespan of your roof, improving aesthetics, and increasing overall weather resistance.

What is the purpose of foam closure installation during flashing installation? 

Foam closure installation during flashing installation fills the gaps between the metal roofing panels and flashing. This adds an insulation layer and safeguards your home against harsh weather conditions.

Where should the screws be placed when fastening the end wall flashing? 

The screws should be placed at the top of the flashing when fastening the end wall flashing. This technique helps prevent water seepage and ensures a secure fit.

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