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The Different Layers of a Roof (And What You Need to Know About Them)

August 20th, 2021 | 7 min. read

The Different Layers of a Roof (And What You Need to Know About Them)

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As you’re walking down the street and looking up at roofs, you only see the top layer. The truth is, your roof is so much more than the just shingles you see. 

Whether you’re just curious or if you’re getting ready for a roofing project, you don’t want to be surprised by all the different materials (layers) you’ll have to pay for when getting a new roof. That’s why you need to know the different roof layers and why they’re important. 

Here at Bill Ragan Roofing, giving you a proper roofing education is our main goal. The first step to this is breaking down the layers/materials that make up your roof. 

Unfortunately, we can’t give you all the important information you need to know about the layers of your roof. That’s why we included hyperlinks to the different materials to provide you with the option of diving deeper into each one.

Let’s get to the different roof layers and what you need to know about them. 

Roof decking 

The first layer of your roof will always be your roof decking (also known as roof sheathing). Roof decking is the wooden boards (plywood or planks) that make up the framing of your roof.

roof decking

I like to say it's the foundation for the rest of your roofing materials and components to be installed on. If your roof’s decking is rotten or it can’t handle materials being installed on it, it’ll need to be replaced when getting a new roof. 

Unfortunately, you won’t know if or how much will need replacing until your old roof is torn off

Drip edge

Drip edge is metal flashing installed at the roof’s edges (eaves and rakes) to keep water away from your fascia and from getting underneath your roofing components.

roof drip edge

If your roof doesn’t have drip edge, water gets behind your gutters and rots out both your fascia board and roof decking. It’s actually a code that your roof must have drip edge and that it’s installed correctly.

Unfortunately, some roofing contractors cut corners by leaving off drip edge to lower their prices or are too lazy to install it correctly. 

When this happens, it’s going to be a lot harder to pass a home inspection because your roof isn’t up to code.

Ice and water shield

Ice and water shield is a waterproof membrane used to protect your roof from ice and water damage. Its main purpose is to protect your roof decking if water gets underneath your roofing material (asphalt shingles, metal roof, etc.).

ice and water shield in valley

It’s crucial to have ice and water shield installed on/around certain areas of your roof, like roof valleys, around penetrations, and on roofs that have a 2/12, 3/12, or 4/12 pitch. Because of its importance, every roof needs to have it.

Roof underlayment 

Roof underlayment is a felt (15 lb, 30 lb, or synthetic) roofing material that sits between your roof decking and your shingles. It’s installed directly over your roof decking and provides an extra layer of protection from the elements.


Underlayment is the last line of defense for your roof if water gets to the decking. Because of its importance, you need to invest in the best underlayment possible. 

Starter shingles

Starter shingles are a pre-cut row of roofing material that goes underneath the first course of shingles before they’re installed. It makes sure that there's roofing material between the joints where the shingles butt against each other on the edges of your roof. 

starter shingles

Starter shingles also have an adhesive to ensure the first row of shingles are sealed at the eaves and along the rakes. This seal helps improve your roof’s resistance to strong winds.

Asphalt shingles or another type of roofing material

This is the layer that most people think of when talking about a roof. This is the top layer of your roof system and will be the type of roofing material you choose (asphalt shingles, metal roofing, cedar shake roofing, synthetic roofing, etc.)

asphalt shingle roof

It will make up the bulk of your roof, and it’s what you see from the street. If you’re unsure what type of roof fits your needs, take this Roof Type Quiz to find the right roofing material for you. 

Roof flashing

Roof flashing is a thin metal material that directs water away from certain areas (walls, chimneys, roof valleys) of your roof. It’s a crucial roofing component that every roof needs to have and is installed at the same time as your shingles. 

roof flashing

Your roof flashing will be made of aluminum, steel, or copper. No matter what kind of metal it’s made of, your roof flashing should outlive the original roof it was installed on. 

This means you might not have to replace it when getting a new roof. However, it’s crucial that your roof flashing is inspected as part of annual roof maintenance to prevent or catch potential leaks.

Ridge capping

After your shingles are installed on all facets of your roof, it’ll be time to install the ridge capping.  Ridge capping is the trim installed at the top of where two slopes of a roof meet. 

ridge capping

Ridge capping is thicker than regular shingles and pre-bent, so they can form to the ridges on a roof. Be aware, some roofing contractors use 3-tab asphalt shingles as ridge capping to cut down their costs for an asphalt roof. 

They’re not designed for this and will lead to a roof leak. That’s why it’s crucial to use the manufacturer’s ridge capping accessory when getting a dimensional or luxury asphalt roof. 

Roof vents

Roof vents allow your attic and home to breathe properly. Without a proper ventilation system, your roof’s life will be cut drastically short. 

roof vents

There are different types of roof vents to choose from depending on your ventilation system. If you have an active ventilation system, you’ll choose turbine vents, power vents, ridge vents with a baffle, or solar-powered vents. 

For a passive ventilation system, you choose from static vents (box vents), ridge vents without a baffle, or gable-end vents. I recommend an active ventilation system for performance reasons. 

However, all the vents do the job if they're installed properly, and your attic is properly ventilated. 

Why proper roof installation is important

Now you know the different layers (materials) of a roof. Most of these materials will be replaced when getting a new roof. 

However, these roof layers mean nothing if they’re not installed correctly during your replacement. That’s why you need to know the importance of proper roof installation. 

Because we want to continue educating you on the important aspects of roofing, we wrote another article breaking down what causes improper roof installation and why it’s important. 

Since 1990, Bill Ragan Roofing has provided high-quality roofing services to the residents of Nashville. Whether you need roof repairs or a full roof replacement, you can count on us to give you a roof that lasts for decades. 

Check out Why Proper Roof Installation is Important to learn everything you need to know about correct roofing techniques. repair or replacement quiz

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