Roof Flashing

When it comes to roofs, the first thing that comes to mind is the shingles. Asphalt shingles are what adds aesthetic appeal to the roofs. They are tough, durable, and stand up to the weather.

Whether it is asphalt shingles, metal panels or clay tiles that your roof is made out of, these are not the only things that are shielding your home from the tough weather conditions. 

Have you ever heard of roof flashing? You may have a roofing contractor or roofing expert casually throw this term at you. Just like the roofing material, roof flashing works just as hard to redirect water away from the roof deck to another spot. 

It doesn’t matter if you have heard nothing about roof flashing before. We’re here to help you out! In this guide, we hope to answer everything you need to know about roof flashing. Even if you know what it’s about, maybe you can do a quick read through so that if you ever need to replace or repair your roof, you will keep the roof flashing in mind and get it done properly.

all about roof flashing

What is Roof Flashing?

Take a nice hard, long look at your roof. Roof flashing is a thin material made out of metal that directs water away from certain spots on your roof, such as the walls, chimneys, and roof valleys.

Otherwise, the water could seep into the seams and joints, and cause damage to your roof deck. No roof is complete without roof flashing.

Materials that go into making Roof Flashing

Now that you know what roof flashing is, you should know what they’re made out of. A variety of materials go into making Roof Flashing. These include copper, aluminium, galvanized steel, lead, and stainless steel. Flashing is also available in Zinc alloy metal. These metals are rolled thin and installed on roofs to protect them from moisture, heavy wind, storms, etc. 

Steel, copper, and aluminium are popular choices. For one, they are malleable. So, they can be framed into any shape. They are also rust-resistant to obstruct water from entering your home and damaging your property. Let’s look more into these metals and why they make for great roof flashing materials.

  • Galvanized Steel is one of the most often used materials for roof flashing. It is because it stands up to corrosion and is a lot more affordable than aluminium and copper. And it will give a nice, clean finish. Further, they are coated with Zinc to lend protection from corrosion and harsh weather elements, as well as to extend the lifespan.
  • Lightweight and easy to mold, aluminium is a good choice for roofing material. However, the durability lies in how well it is coated. Aluminium will come apart when it comes in contact with alkaline surfaces. But when coated, it can be made to last long and used over stones and concrete. Your roofing contractor may coat Aluminium with Masonry to prevent corrosion. Moreover, if you like doing things by yourself, then Aluminium is the right choice for you because it is easy to bend and mould. For tackling the tricky sections of the roof such as chimney, base, and valley flashings, Aluminium is the best choice due to its malleable nature.
  • Copper is one of the best choices for roof flashing and is very durable. However, it could discolor as time passes. If your roof is made out of copper, it makes more sense to go with copper material for your roof flashing. And this added aesthetics and long-lasting capability come at a cost. But being malleable and easy to solder, it is one of the more popular choices. If you don’t mind the cost, and the fact that with age, copper tends to fade into a patina, then you can very well go with copper. It does not require any coating or regular maintenance either. 

In very rare cases, roof flashing is made out of plastic, rubber, or roof felt. You need to have a conversation with your roofing contractor to find the best roof flashing material for you.

What does Roof Flashing Do?

Roof flashing is crucial to ensure that the water doesn’t get under your shingles. The parts of the exterior wall and roofs prone to corrosion and water leakage could do with roof flashing. Flashing simply collects the rainwater and redirects it to some other location, say, the drainage. This is what a Flashing does, no matter where it is installed – it protects the crucial areas of your roof.

The primary purpose of roof flashing is to close a joint in the exterior wall of your home or other roofing application to prevent water from leaking into the materials that go into building the roof or wall in the first place. 

Roof Flashing can be installed in the following places:

  • Valleys
  • Sidewalls, front walls and any exterior wall!
  • Roof edges
  • Roof protrusions
  • Chimneys
  • Gutters
  • Skylights and vents.

Agreed, roofs are there for making the water run-off. There are some vertical components or protrusions in your roofs, such as chimneys, dormers, kitchen vents, chimneys, skylights, and such. The water can collect in the narrow openings on such spots. The result? Damage to these spots and the water will corrode into the house. To stop water leakage, roof experts will apply roof flashing and divert the rainwater down the sides of the vertical protrusions. So, no water stagnation means no damage!

Types of Roof Flashing

1. Base Flashing and Step Flashing

Base Flashing: Roofing components that require two pieces of flashing are ideal for Base Flashing. The major advantage of base flashing is that they are easy to install. The water is guided away from the roof. Base flashing moves along with the two pieces of flashing, and with weather changes, the roofing material expands and contracts.

Base flashing sits at the joint between your roof and the front wall or chimney.

Step Flashing: Step flashing is rectangular in shape. It is bent at a perpendicular angle to the roof pitch and installed along the entire length of the sidewall where it meets the roof deck. Generally, several layers of step flashing are installed with shingles to ensure the water is directed away from the wall.

Now, unlike base flashing, step flashing is apparent from the ground. So, you could go with a metal that you think will give a more aesthetic finish.

2. Apron Flashing

Shaped in the form of the letter “L”, it can run up to 14 feet in length. It is a long, single piece of metal that is used to fit the wall base or any roof penetration. The rainwater collected is carried down to the shingles located below. Have dormers on your roof? Apron or continuous flashing can be used to guide water away from the windows.

3. Counter Flashing

Remember, we said base flashing requires two pieces of flashing? Well, counter flashing is the second piece to complete the base flashing. It is installed on top of the base flashing or opposite to it. The flashing is first sawed into an existing mortar joint, and on top of the brick comes the metal. It is used for walls, chimneys, and skylights. Once the base and step flashing have been installed, the counter flashing is done. 

The counter flashing will be mortared right in front of the chimney. There will be very little space between the base of the counter flash, and the next line of shingles. This way, the water will simply run down the roof slope without sneaking into the chimneys or walls.

4. Chimney Flashing

Chimneys are one of the most complicated aspects of roofing that is really bad when it comes to allowing water in. So, nowadays, flashing is used to stop this issue entirely. Two types of flashing are used in the case of chimneys. The first one is base flashing which sits directly on the shingles. Then comes the Counter flashing on the top. So, it’s shingles, base flashing, and then counter flashing in that order. 

5. Valley Flashing

You know what valleys are right? Two roof decks slope towards one another and meet at a low line. Now, as far as roof valleys are concerned, the flashing material is installed underneath the roof shingles at the very edge. As the rainwater pours down, it flows down the valleys from the shingles the exact same way water flows down from the valley between the mountains. This water either drains into the gutter below or down the next layer of shingles.

6. Drip Edge Flashing

Edges of the roofs mean eaves and rakes. As the name suggests, drip edge flashing is metal flashing fitted along the edges of the roof. They are installed at the edge of your roof to prevent water from seeping under the roofing where there are rakes and eaves. They are crucial along with the rakes, but they are effective along the eaves as well. 

If your home is located at a place where it is highly windy, then the flashing integrated at the rake edges will protect your roofs to a great extent. You don’t want the shingles to be lifted right off due to a particularly strong gust of wind now, do you! At the eaves, on the other hand, the drip edges wrapped at the eaves will help to shield the wood right below the shingles(this is called fascia). This is the case where there is no gutter.

7. Skylight Flashing

More often than not, your skylight will come with flashing. If not, your roof contractor should get it done. Your skylight must have some sort of flashing in place to prevent rainwater from leaking inside. 

Skylight flashing will fortify your roof from moisture and resist mold, corrosion, roof root, and in worse cases, structural damage to the roof as a result of water seepage. 

8. Kickout Flashing

Kickout flashing is a basic flashing that works by redirecting the moisture and rainwater away from the edge of a roof section and into the gutter. Its main focus is to prevent damage to the sides of the walls in your home.

Does Roof Flashing Ever Need Replacement?

If you are thinking about replacing a roof, you may be wondering if your roof flashing needs to be replaced as well. The answer is, maybe! 

Roof flashing is installed over the roof material and in an ideal world, it should outlive the lifespan of the original roof over which it was installed. So, they can be reused again.

Your roofing contractor will inspect your flashing when they purview your roof for replacement. If they deem that the metal integrity is great and they find absolutely no signs of rust, then there will not be any need for getting your roof flashing replaced when you go for roof replacement. If there are any signs of damage or rusting, then the roof flashing will have to be replaced when your roof is replaced. Watch out for any signs of rust, holes, corrosion, damage, or wear. If you can see now, your roofing contractor will recommend the reuse of roof flashing.

Why Should You Check Your Roof Flashing Regularly?

When you carry out your regular roof maintenance and inspection, ensure to check up on your roof flashing as well. This could be super helpful to prevent a roof flashing problem even before it ever happens. Also, ensuring that the integrity of the metal is holding strong is important during your regular roof maintenance check as this will help you rest assured that the Roof Flashing you have put up is doing the job it was installed for in the first place. 


The concept of roof flashing is simple. It is a thin metal layer made out of different materials (galvanized steel, aluminium, and copper are the predominant ones used) to redirect water away from the roof and prevent damage to your home. 

There are several varieties of roof flashing and quite a few choices of materials for flashing. The right roof flashing for your home is entirely dependent on the kind of roof you have at home. The style of your home, the weather conditions, the shingles you have selected for your roof will all play a major role in determining the kind of roof flashing you will go with. We hope this guide will help you in picking the right flashing for your roof. 

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