When you look at a finished roof, almost everything you see is shingles. That can make it seem like a roof is simply a layer of shingles nailed onto the top of a house.

There’s actually an entire roofing system underneath them.

At Barringer Brothers Roofing, we’ve served homeowners throughout Belleville, IL and the Metro East since 2004, earning 200+ five-star reviews. When we install an asphalt roof, the shingles are only one part of the finished system. Decking, underlayment, edge protection, flashing, ventilation, and other components all have their own jobs.

So, if you could peel an asphalt roof apart layer by layer, what would you actually find?

1. Roof Decking: The Base of the Roof

Starting at the bottom, you have the roof decking, sometimes called roof sheathing.

This is the solid surface attached to the home’s roof framing. It’s what the roofing materials are ultimately installed over and provides the structural base for the roofing system.

On many homes, the decking is made from plywood or OSB.

When an existing roof is replaced, removing the old roofing materials gives the crew an opportunity to see the decking more clearly. If damaged or deteriorated areas are discovered, those areas may need to be addressed before the new roofing system can be installed.

One thing homeowners sometimes misunderstand is that getting a new roof doesn’t automatically mean getting all-new roof decking.

If existing decking is suitable for the new installation, it doesn’t necessarily need to be removed simply because the shingles are being replaced.

2. Ice and Water Protection: Extra Protection in Vulnerable Areas

The next component you may find is an ice and water barrier.

Unlike standard underlayment that covers broad areas of the roof, ice and water protection is a self-adhering material commonly used in particularly vulnerable areas of a roofing system, depending on the roof and installation requirements.

These can include areas where water is more likely to collect or where additional protection is beneficial.

It’s essentially an extra layer of defense underneath the finished roofing materials.

And because it disappears underneath the roof once installation is complete, most homeowners never see it again.

3. Roofing Underlayment: What’s Directly Under the Shingles?

Over the roof decking is roofing underlayment.

This creates another protective layer between the decking and the shingles.

It’s easy to think of shingles as the only thing standing between your house and rain, but a properly installed asphalt roofing system uses multiple components rather than relying on one exterior material alone.

During installation, you’ll often see large sections of the roof covered in underlayment before the shingles are installed.

Once the job is finished, that entire layer disappears from view.

4. Drip Edge: The Metal Along the Roof’s Edges

Around portions of the perimeter of the roof you’ll find drip edge.

Drip edge is metal flashing installed along roof edges. Its job is to help direct water away from vulnerable edges of the roofing system and toward the appropriate drainage path.

It’s a relatively small component compared with thousands of square feet of shingles, but roof edges are exactly where installation details matter.

From the yard, you may be able to see a thin strip of metal along the edge of your roof without ever realizing it has a name.

That’s your drip edge.

5. Starter Shingles: The First Shingles You Barely See

Before the main field shingles begin, there’s another component homeowners rarely think about: starter shingles.

Starter shingles are installed along designated roof edges before the regular shingles.

They’re specifically designed to provide the proper starting course and help secure the shingle system at the edges.

You generally won’t look at a completed roof and think, “There are the starter shingles.”

That’s because they’re incorporated underneath the first visible course of shingles.

They’re another example of something that’s important during installation but mostly disappears once the roof is finished.

6. Asphalt Shingles: The Part Everyone Recognizes

Now we finally get to the part you actually see: asphalt shingles.

Shingles make up the primary visible exterior surface of the roofing system.

At Barringer Brothers Roofing, we install CertainTeed asphalt shingles for residential roofing projects.

Shingles aren’t simply there to make the roof look finished. They’re installed in overlapping courses so water moves down the roof toward its edges rather than directly reaching the materials underneath.

Shingle choice can also dramatically change the appearance of a home. Color, pattern, profile, and the overall roof design all contribute to how noticeable the roof is from the street.

But even high-quality shingles still depend on everything underneath and around them being installed correctly.

7. Flashing: Protection Where Things Get Complicated

A roof isn’t always one uninterrupted surface.

It can meet walls, chimneys, vents, and other structures. Those transitions require special attention because water needs to be directed away from areas where different materials or surfaces meet.

That’s where flashing comes in.

Roof flashing is typically made from metal and is installed in specific areas to help direct water away from vulnerable transitions.

Depending on the home, you may find flashing around chimneys, where a roof meets a wall, and in other areas requiring additional water management.

Flashing isn’t really a single “layer” covering the entire roof like underlayment. Instead, it’s incorporated into the roofing system where it’s needed.

8. Pipe Boots: Sealing Around Plumbing Vents

See a pipe sticking through a roof?

There needs to be a way to seal the roofing system around it.

That’s where a pipe boot comes in.

Plumbing vent pipes need to pass through the roof, which creates what roofers call a penetration. A pipe boot is installed around the pipe to help create a weather-resistant seal where it passes through the roofing system.

It’s a small component, but it’s a great example of why a roof is much more complicated than simply laying shingles across a surface.

Every penetration has to be properly incorporated into the roofing system.

9. Roof Ventilation: Helping Air Move Through the Attic

Your roofing system may also include ventilation components.

One common example is the ridge vent we recently talked about.

A ridge vent is installed along eligible roof ridges and serves as exhaust ventilation for the attic. When paired with appropriate intake ventilation, it helps create airflow through the attic space.

Depending on the home and roof design, other ventilation methods may be used instead.

Like flashing, ventilation isn’t technically another continuous “layer” of the roof. It’s a component incorporated into the complete system.

10. Ridge Cap Shingles: Finishing the Peaks

Look at the very top of a finished asphalt roof and you’ll see shingles covering the ridges and, depending on the roof design, hips.

These are ridge cap shingles.

Regular field shingles are designed primarily for the main roof planes. Ridge caps are designed to finish areas where roof planes meet.

If a ridge vent is being used, ridge cap shingles can also be installed over that ventilation system, giving the ridge its finished appearance while the vent underneath continues doing its job.

So What Is Actually Under Your Roof Shingles?

If we simplify everything, a typical asphalt roofing system may include:

Roof structure → decking → protective membranes/underlayment → starter components → asphalt shingles → ridge caps

Then components such as drip edge, flashing, pipe boots, and ventilation are incorporated into the system where they’re needed.

The exact assembly can vary depending on the roof, home, product requirements, and applicable installation requirements.

That’s why thinking of a roof as “just shingles” doesn’t tell the whole story.

Why Do All These Layers Matter?

Because your roof doesn’t depend on one product to do everything.

Different components handle different jobs.

The decking provides a solid base. Protective materials beneath the shingles add another layer of defense. Flashing handles transitions. Pipe boots address penetrations. Ventilation helps manage attic airflow. Shingles form the primary exterior roof covering.

When everything is installed together correctly, you get a roofing system, not simply a surface covered in shingles.

That’s also why two contractors quoting the same house aren’t necessarily proposing identical roofing systems just because both estimates say “asphalt shingles.”

The details matter.

Why Can’t I See Most of This From the Ground?

Because you’re not supposed to.

A properly finished roof hides many of its most important components.

Once the shingles and finishing materials are installed, you won’t see the decking or most of the underlayment. Starter shingles blend into the finished system. A ridge vent can be covered with ridge caps. Portions of flashing may be tucked beneath surrounding materials.

That’s one of the interesting things about roofing:

A lot of the work that determines how the finished roof is put together is work you’ll never see once it’s done.

That’s why photos taken throughout a roofing project can be useful. They give homeowners a look at parts of their roof that will eventually be completely covered.

Frequently Asked Questions

Have Questions About What’s Actually on Your Roof?

You don’t need to know every roofing term before hiring a contractor, but understanding the basics can make it much easier to understand what you’re actually paying for and what’s being installed on your home.

Barringer Brothers Roofing has served homeowners throughout Belleville, IL and the Metro East since 2004.

Want to learn more about your current roof or what goes into a new asphalt roofing system? Call Barringer Brothers Roofing at (618) 703-3036 or fill out our online contact form for more information, to schedule an inspection, or to request an estimate.