An Essential Guide to Metal Roof Flashing

Jun 20, 2023


Viking Contractors




June 20, 2023


May 10, 2024

Got Questions?

A metal roof is an important investment as it’s durable, energy-efficient, and protects us from the elements for a long time. However, there’s another component that ensures your building is leak-free, and that’s the metal roof flashing. 

Because of its critical nature, we’ll provide all you should know about roof flashing and how to choose one for your metal roof.

Overview of Metal Roof Flashing

Flashing is a thin material consisting of aluminum or galvanized steel. Although it can be made of rubber or plastic, the metal variant is appropriate for a metal roof.

A metal roof flashing is installed in intersections between surfaces and the roofing material. You can find it around valleys, ridges, dormers, chimneys, skylights, and vents.

Hiring a roofing professional to install your metal roof flashing ensures that water moves away from critical areas of your roof, safeguarding the edges from leaks. And if water can’t get into your building, there will be no room for mold, mildew, wood rot, and damaged decking.

Types of Metal Roof Flashing

Old brick chimney pots on a victorian building roof against a blue sky background

There are different types of metal roof flashing for specific purposes. Below are the types of flashing for a standard metal roof:

Step Flashing

Step flashing is installed in areas where the roof meets with vertical points, such as chimneys, walls, and any elevations on the roof. Several pieces of the material are made to overlap each other in steps as they move up the wall.

Counter Flashing

This type of flashing is installed on a brick wall to cover the step flashing and direct water down the siding. It’s inserted into mortar joints or grove cuts and sealed with an appropriate sealant.

Base Flashing

This is a two-piece flashing that directs water downwards when it hits the chimney. And because it’s installed at the base of the chimney, it won’t affect the entire structure when the roofing material expands and contracts.

Valley Flashing

Valley flashing is a w-shaped material installed in the valley or lowered portions of the roof where two planes meet. 

Apron Flashing

Apron flashing is also known as continuous flashing because it’s a long metal piece that guides water downwards. A professional will install inbuilt expansion joints to prevent the flashing from warping or breaking when it expands and contracts.

Kickout Flashing

Kickout flashing bridges the gap between the end of a step flashing and the beginning of the gutter. It ensures that water moves directly into the gutter.

Drip Edge Flashing

Drip edge flashing is installed above the edge of the roofing material and beneath the gutter. It helps water drip off the roof and into the gutter without spilling.

Ridge Cap Flashing

The ridge cap flashing is placed at the apex of the roof. It protects the roof from the impact of strong winds and seals the sheets to reduce the occurrence of leaks.

Materials for Metal Roof Flashing

Metal huse flashing wrapped in Plastic for delivery

Just as there are different types of metal roofing, you’ll find the same materials when choosing the flashing for your roof.

Galvanized Steel

Steel is aesthetically pleasing and resistant to corrosion when galvanized. The contractor can solder a galvanized steel flashing when used around joints, leaving no room for water seepage. Although the metal can last for up to 40 years, it’s thick and difficult to tell when it’s ripping off.


Aluminum flashing is versatile because it’s relatively cheap and lightweight, and contractors can easily manipulate it. And it can last for over 20 years or more if properly maintained. 

Unlike steel, aluminum doesn’t require soldering as it could break. And if left plain, it may corrode within a short time. Therefore, aluminum flashing should be coated and handled with care.


Copper is the most reliable material for roof flashing. It’s malleable, durable, and can be soldered. It also has a shiny appearance that improves curb appeal. However, the material forms a patina, which some homeowners may not like.

Contractors can easily work with copper because it’s lightweight and forms various shapes. But the major drawback is that it’s the most expensive roof flashing material. So if you’re going for copper, you may want to consider roof financing before making the next move.

Metal Roof Flashing Installation Techniques

Roofer construction worker repairing chimney on grey slate shingles roof of domestic house

Because every part of the roof requires adequate protection, you’ll find flashing for each feature. However, the technique applied during installation isn’t the same. Below are three popular roof flashing installation methods.

Peak Trim

Peak trim is utilized when installing ridge cap flashing at the highest point of the roof. It prevents moisture from penetrating the sloping panels below. The installation process involves applying a tape sealant and a tube sealant. The trim should also have the right cut and angle and should be folded and fastened securely.

Rake Trim

Rake trim is also known as the gable trim. It’s installed along the edges of your metal roof line and can serve as a finishing piece, covering the nails on the gable. The installer would ensure that the trim meets the eave and end wall and is properly sealed and fastened using appropriate spacing.

Eave Trim

An eave is the overhanging edge of a roof. And the eave trim, also known as the eave drip, is fixed at the edge of a metal roof panel. It sends runoff rainwater away from the roof fascia down to the center of the gutter. 

Unlike the other trims, the eave trim doesn’t involve much angling to get the right fit. But you should consider installing an underlayment to prevent moisture from penetrating the flashing.

Choosing the Right Flashing for Your Metal Roof

Before going ahead to buy flashing for your metal roof, here are some things you should consider:

Compatibility With the Roofing Material

Metal roof flashing is made of various materials: steel, copper, and aluminum. You should consider using one that matches the existing roofing material for durability and longevity. For instance, you shouldn’t use copper flashing with an aluminum roof because it would result in galvanic corrosion.

Weather Conditions

If you live in an area that experiences harsh weather conditions almost all the time, you should choose a flashing material that can take beatings from the elements. Copper flashing is ideal for humid areas as it’s resistant to rust and corrosion. Aluminum, on the other hand, goes well with dry and hot areas.

Roof Flashing Sizes

The roof feature will determine the size of the flashing you’ll purchase. If you’re flashing a plumbing vent, it should be wider than the diameter of the vent. This will ensure adequate coverage and reduce the risk of leaks.

Availability and Cost of the Material

You should check the roof flashing material that’s readily available in your area. For instance, some suppliers may not have copper, which may require ordering from another location. 

Also, each type of metal roof flashing material has a price range, with aluminum being the most affordable. Therefore, you should consider how much you’re willing to spend on the roofing project. 

Quality of the Material

Not all metal roof flashing materials are equal; some last longer than others. However, you should ensure to purchase from a reliable supplier that can offer a warranty. Before choosing a supplier, you should check their customer reviews online so you can rest assured that the investment is worthwhile.

Tips for Maintaining Metal Roof Flashing

Roof flashing is a part of the roof system and requires regular maintenance. The following tips would assist in proper flashing maintenance:

  • Trim any overhanging tree branch that may fall on the flashing during heavy wind or rainfall.
  • Clean the flashing and gutter to remove debris, as any accumulation may result in drainage issues, which increase the risk of leaks.
  • Check for rust and apply a suitable coating.
  • Look out for missing flashing so you can contact a professional to replace it immediately.
  • Sign up for a periodic roof inspection to get a comprehensive assessment of your roofing system.

Signs of a Failing Roof Flashing

Do you have to wait for a leak before replacing or repairing your flashing? Below are some tell-tale signs of faulty flashing:

  • The material has holes or dents
  • It’s rusted with visible signs of corrosion
  • The nails are loose or missing
  • The flashing is either loose or missing
  • Water stains on the wall  
  • The sealant is dried, cracked, or missing
  • Growth of mildew and mold in the attic or on the ceiling and walls

Final Thoughts

Proper flashing installation ensures your roofing material lasts longer and saves you the cost of water damage. A metal roof flashing is a major investment, and you don’t want to ruin it by undertaking a DIY project. Hence the need to contact a roofing professional who’ll supply quality materials and offer you a reasonable warranty. 

Remember to maintain your roof flashing to ensure its durability. And inspecting the flashing periodically also helps you know when something is amiss so you can take appropriate action. A professional roofing contractor can offer this service at a minimal cost.

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