Guide to Roof Flashing

What is flashing on a roof? Flashing is simply impermeable material put on joints in your roof and construction walls. Roof flashing prevents water from seeping in and bringing about serious damages to your home.

There are different types of material you can use for your roof flashing, as we will discuss later on in this article. First, let’s look at the purpose of flashing on a roof. And how it works. So you can understand its importance. And why you should make an effort to ensure your roof flashing is always in good shape.

What is the purpose of flashing on a roof?

Flashing is essential when it comes to your roof because it offers protection from roof leaks and severe water problems that may arise.

It (flashing) also protects the internal sections of your roof from harsh weather damage.

Therefore, it is critical for certain parts of your roof. Including the areas where your roof surface meets the walls (the front and side walls), the valleys, i.e., the low sections where the slopes of your roof meet, the roof’s edges, and any protrusions.

Roof protrusions where most homeowners install flashing include skylights, bathrooms, and kitchen vents.

How does roof flashing work?

The impermeable material helps to direct water flow around your roof openings preventing water from getting in. And, destroying your home.

Commonly, you can install flashing material as thin pieces or one long piece (continuously) in roof openings. Including the areas we looked at above. This way, flashing protects your roof- appropriately- at all times.

Without proper flashing- water can easily penetrate your home through the roof joints and openings, causing structural damage and severe mold problems.

Leaks from these joints can also weaken your entire roofing system. By causing the building materials underneath to deteriorate. And, when this happens, you’ll be faced with serious water damages that are very expensive to repair.

This is why you must make sure your roof flashing is always in good shape.

What materials can be used for roof flashing?

There are 6 types of material you can use for roof flashing purposes. These 6 options include plastic, rubber, galvanized steel, copper, aluminum, and roofing felt.


You can use Polyvinyl Chloride (Pvc) plastic as a waterproof flashing material. It is strong and durable. However, Pvc cannot be in close contact with asphalt making it an unsuitable flashing material for some roofs.


Rubber is a good material for flashing. Because it can adhere to the joints properly hence offer maximum protection for your roof.

rubber roof flashing

The downside of using rubber as a flashing material is the fact that it is flammable. Therefore, it poses a serious risk for fire outbreaks.

Also, it is not the most long-lasting option you can make since rubber easily weakens and tears over time.

Galvanized steel

Galvanized steel is the most durable material for roof flashing. Because of its robust nature, steel is extremely long-lasting, which makes it the most economical purchase you can make.

galvanized steel roof flashing

Galvanized steel is also rust-proof and requires very low maintenance. As a result, you can confidently leave this type of flashing unchecked for a while without worrying about damages or malfunctions.


You can only use copper roof flashing alongside copper roofing. Since such flashing is custom-made to fit each specific copper roofing system.


Aluminum is the most popular roof flashing material.

aluminum roof flashing

Most people prefer using aluminum material because of its malleable nature. You can bend aluminum flashing into any shape with little force. Thus, effectively protect roof or roof features with an odd shape.

Roofing Felt

Roofing felt looks a lot like tar paper. It is the foundation material that manufacturers use to make shingles.

As a flashing material, you are better off using roofing felt alongside another material. Because, the felt alone will not give your roof full waterproof protection.

Also, the roofing felt is not very strong or durable compared to other materials that are readily available for you to use for flashing.

Roof Flashing Types

There are approximately 6 types of roof flashing, all named after the place where one installs the roof flashing material.

Continuous Flashing

As the name suggests, you put continuous flashing as one long piece. Mostly, you can put this type of flashing on the joints where your roof slopes and attaches itself to the vertical walls.

Valley Flashing

Valley flashing offers protection against water damage that may arise as a result of water seeping into your home- through the sections where the two valleys of your roof planes meet.

valley flashing

Because it follows the shape of your roof valleys, you’ll find that valley flashing material takes the shape of a W. During installation, valley flashing is put on top of roofing felt within your roof valleys.

Drip Edges

You’ll find this type of flashing on the eaves of your roof.

Commonly referred to as edges, the eaves of your roof are the sections that overhang on the face of your walls. And, usually, protrude beyond the sides of your entire building.

Generally, you install drip edges flashing under the roofing felt- along these roof eaves. In order to prevent water from seeping or soaking underneath these edges.

Step Flashing

You can easily notice step flashing on your roof’s horizontal segments. And vertical roof fixture. Normally, you have to shape the material you are using for this purpose to fit the specific horizontal or vertical section of your roof.

It is best to install this type of flashing in an overlapping manner. So as to prevent water from getting behind and causing serious roof water problems.

Cap Flashing

Cap flashing material takes an L-shape.

Because of its shape, you can always set it up to lie flat against your roof. Or any other fittings in your home, including your windows.

The L shape of cap flashing structures lets water runoff in the opposite direction. This prevents water from collecting in any cracks or around the areas where you put cap flashing.

Vent Flashing

Vent flashing appears like a cone. You fit it into your roof shingles to cover and protect pipes.

Saddle Flashing

You can easily use saddle flashing to cover, thus protecting railing attachments. And protruding beams.

Where are flashings used?

Common examples of flashing you are likely to find in most, if not all, households include chimney flashing and skylights.

Chimney flashing

Chimney flashing is installed around chimneys. To prevent water from collecting within the gaps found between your roof and chimney bricks.

Chimney flashing

Often, homeowners prefer using PVC or metal flashing material.

For this purpose, you can install different types of flashing. You’ll notice most homeowners prefer using continuous flashing across the bottom area of the chimney. At the same time, covering and protects its sides with step flashing.

You can also caulk in cap flashing to overlap the other types of flashing you use around your chimney. As a way of preventing water from running behind these flashings. This protects your home from any form of water damage that is likely to arise from your chimney area- fully.

Roof windows or Skylights

Skylights have an in-built flashing preventing water from oozing in. However, most homeowners add their own flashing for maximum protection.

Often, homeowners choose to fit continuous flashing along the roof window’s base. On the sides, they install step flashing while using saddle flashing to cover and protect the top part of the roof window.

Final thoughts

Is roof flashing necessary? The short answer is yes, roof flashing is necessary. This form of protection for your roof is a required practice in construction. As a result, it is applied widely to all structures be it residential, commercial, or industrial buildings.

In addition, note that flashing is not just installed on your roof. You can also set up flashing in other parts of your home as well.

For instance – You can install flashing above all interior wood trims on top of shelves, windows, and doors. And, in the sections of your household where outdoor decks and stairs attach to the house. Flashing is also mounted underneath the first course found above ground level within a masonry structure.

What is the condition of your roof flashing? Do you have any regular roof maintenance practices that have worked well for you so far?

Mas Broto

Written by: Mas Broto

Mas Broto is a small business owner with 30 years experience in the real estate industry. He is the founder and editor of, the most comprehensive free home improvement website on the planet!