The 10 Asphalt Shingle Roof Components

Is it time for a new asphalt shingle roof? Are you wondering what different materials and components you'll pay for when getting an asphalt roof replacement?

When most people think about an asphalt shingle roof, they think about asphalt shingles. However, an asphalt shingle roof is a actually combination of different components coming together like puzzle. 

Not only does each one impact the cost, but they all have a specific purpose to prevent roof leaks. The last thing you want is to have your investment ruined because a roofing contractor didn’t install a crucial component.

So, let's help you avoid this happening to you. 

For over 35 years, Bill Ragan Roofing has helped homeowners understand the ins and out of their roofing project. Because of this, I’ll break down the asphalt shingle roof components and why they’re important.

This article covers the following asphalt shingle roof components:

• Roof decking 
• Drip edge
• Underlayment 
• Ice and water shield
• Roof flashing
• Starter shingles
• Asphalt shingles
• Ridge and hip capping
• Roof vents
• Pipe boots

1. Roof decking

Roof decking (also called roof sheathing) is the wooden foundation (plywood or planks) that your entire asphalt shingle roof is installed on. There are two types of roof decking: plank decking and sheet decking.

Plank decking is made up of elongated and rectangular wooden boards that are either 1x6 or 1x8, depending on the span of your rafters. Sheet decking (or sheathing) is literally flat sheets of wood (plywood or OSB) that are much wider than planks.

OSB (oriented strand board) is wood chips/strips compressed together to form a flat 7/16” sheet, while plywood comes in several different thicknesses (⅜”, ½”, ⅝”, and ¾”). Any rotten or compromised roof decking must be replaced before installation can begin.

However, your roofing contractor won’t know how much will need replacing until after the tear off process of your roof replacement.

2. Drip edge

Drip edge is metal flashing installed at an asphalt shingle roof’s edges (eaves and rakes) to prevent water from getting underneath the roofing material and underlayment. Without it, your fascia board and roof decking’s edges will rot from prolonged exposure to water. 

Drip edge is also required per building codes and must be installed correctly for your home to pass an inspection. Unfortunately, I see too many asphalt roofs without drip edge.

While it can be left off by laziness or lack of experience, bad roofers knowingly exclude it from their estimates to lower prices. If your roof estimate doesn’t have a line item for drip edge, I recommend finding another roofer altogether.

3. Roof underlayment

Roof underlayment is a felt or synthetic material installed directly over your roof decking before the asphalt shingles are installed. Its purpose is to provide a layer of protection for your decking if water gets underneath the shingles. 

The two types of underlayment options are felt and synthetic.

Felt underlayment has been around the roofing industry longer than synthetic and comes in 15 lb. and 30 lb. rolls. Both types do the job, but 30 lb. felt underlayment is thicker, stronger, and less likely to tear than 15 lb.

Synthetic underlayment is made out of woven/spun polyethylene or polypropylene, which means it won’t hold moisture. It’s more durable, holds nails better, and repels water better than felt underlayment.

Felt isn’t a bad choice, but I recommend spending the extra money for the functionality and better water protection synthetic underlayment offers.

4. Ice and water shield

Like underlayment, ice and water shield is a waterproof membrane that protects the decking from ice and water damage if it gets under the asphalt shingles. But unlike underlayment, it’s installed on/around certain problem areas that need added protection instead of over the entire roof deck.

(Ice and water shield installed in a roof valley)

Ice and water shield is mainly installed in roof valleys, around penetrations, and on asphalt shingle roof facets with a 2/12, 3/12, or 4/12 pitch. But if you live above the snowline in the US, building codes also require two rows of it along the edges of your roof to prevent leaking from ice damming.

This is considered an "upgrade" in areas like Middle Tennessee to prevent ice damming leaks when we get heavy snowfall.

5. Roof flashing

Roof flashing is a metal material that directs water away from areas (walls, chimneys, roof valleys) where shingles butt up against something. It’s one of the most important components, and you’ll definitely have roof leaks without it.

(Counter flashing on a brick chimney)

Roof flashing can be any metal type, but aluminum, steel, and copper are the most common metals. Also, the specific type of roof flashing used depends on where it's installed and the building material it's installed against.

The main types of roof flashing are:

• Counter flashing
• Step flashing
• Apron flashing
• Valley flashing

While roof flashing usually outlives the other components, it's always recommend replacing it when getting a new roof if the existing metal is questionable. This is simply to prevent future problems and ensure everything installed on your asphalt shingle roof is the same age.

6. Starter shingles

Starter shingles are an asphalt-based roofing accessory used as the first course of shingles on the edges of asphalt roofs. They look like shingles without the tabs but are thinner and pre-cut for easy installation.  

Starter shingles are installed along the rakes and eaves over the underlayment before the actual shingles are installed on top of them. Once installed, the starter shingles adhere to the first row of asphalt shingles, which seals them at the edge to prevent wind uplift.

7. Asphalt shingles

The asphalt shingles are the top layer visible to the outside world and make up the bulk of your roof. There are three types of asphalt shingles to choose from, 3-tab, architectural, and luxury.

Each type of shingle has different warranties, lifespans, and price points. The great thing about asphalt shingles is that there are plenty of color and style options to fit any budget.

Just know that the type you choose has a huge impact on the final cost of your asphalt shingle roof replacement. 

8. Ridge and hip capping

Ridge capping is installed where two slopes meet to completely seal your roof system at the very top. It'll be the same color as the shingles and pre-bent to form perfectly on a roof’s ridge.

While ridge capping is needed on the ridge, there's also hip capping on hips. The important thing is that any capping is actually the capping accessory and not 3-tab shingles. 

They aren't meant to be used this way and bad roofers do this to cut costs to provide a cheaper estimate.

9. Roof vents

Roof vents allow your attic and home to breathe properly by pulling fresh air through intake vents before pushing it out of exhaust vents on the roof. There are multiple vent options, but the type of ventilation system (active and passive) narrows down the choices. 

For an active ventilation system, the most common options are turbine vents, power vents, ridge vents with a baffle, or solar-powered vents. For a passive ventilation system, you’ll have static vents (box vents), ridge vents without a baffle, or gable-end vent.

While certain vents are better for certain roof styles, I recommend an active ventilation system for performance reasons. But no matter the system, it’s crucial that your attic is ventilated properly to avoid your asphalt shingle roof failing prematurely.

10. Pipe boots

A pipe boot (also called roof boot) is a type of flashing that goes around the base of the pipes coming out of your roof. Without them, water leaks down the pipes into your attic and home. 

Depending on the roofing material and type of pipe, pipe boots can be synthetic rubber, plastic, lead copper, etc. While you have these options, the most common type of pipe boot used on roofs today is a synthetic rubber called neoprene.

Just know that neoprene pipe boots will need replacing every 10 years or so once cracks form. However, they’ll be cheaper than copper (or another metal), more durable than plastic, and won’t attract animals like lead.

Which asphalt shingle is right for you?

Now you know the components that make up an asphalt shingle roof. Every one of these components impacts the cost of your new asphalt roof, but not as much as the asphalt shingle you choose. 

That’s why it’s crucial to make the right decision when looking at the three different shingle options. But do you have the confidence to make this decision on your own? 

If you answered no, you’re not alone, and that’s nothing to be ashamed of. Most homeowners simply don’t have the information needed to decide which one is right for their situation, budget, aesthetic, and more. 

That’s why I wrote another article breaking the pros, cons, pricing, lifespan, and much more for the different types of asphalt shingles. 

Check out The 3 Types of Asphalt Shingles to get the information you need to confidently make the right purchasing decision.