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What is Roof Underlayment? (Types, Cost, and More)

October 5th, 2022 | 4 min. read

What is Roof Underlayment? (Types, Cost, and More)

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There are a number of different roofing components and materials that make up your roof system. Each one is important and performs a certain function to keep you and your family dry. 

One of these crucial components is roof underlayment. But what is roof underlayment, and what does it do? 

For over 30 years, the team at Bill Ragan Roofing has helped homeowners understand everything that goes into their roof replacement. That’s why I’ll break down what roof underlayment is and what you need to know about it. 

This article answers the following questions:

  • What is roof underlayment and the types of underlayment?
  • Which roof underlayment is more durable?
  • Which roof underlayment weighs more?
  • What roof underlayment costs more?

What is roof underlayment?

Roof underlayment is a roofing component installed directly over the top of your roof decking. It lies between your decking and roofing material to provide an extra layer of protection from the elements.

There are two types of roof underlayment: felt and synthetic. 

Felt underlayment has been around the longest and comes in two options, 15 lb and 30 lb felt rolls. The main difference between the two types of felt underlayment is that 30 lb is thicker, stronger, and less likely to tear than 15 lb. 

synthetic roof underlayment(Synthetic roof underlayment)

Synthetic underlayment has been around for about 20 years and was developed as technology improved. As the name says, this underlayment is a synthetic material made out of woven/spun polyethylene or polypropylene. 

No matter which type you choose, roof underlayment is a crucial component of your roof system. If it’s left off during your roof replacement, you’ll definitely have problems down the road. 

Which roof underlayment is better?

Both types of roof underlayment have their place in the roofing industry. However, there are comparisons to keep in mind when deciding which one you want on your roof.

To help you determine which one is right for you, I’ll compare felt and synthetic underlayment on weight, price, and more. 

Which roof underlayment is more durable?

Both types of roof underlayment do the job of providing an extra layer of protection. However, synthetic underlayment is more durable than felt underlayment. 

Felt underlayment is more prone to rip in the event of high winds and absorbs water if it gets wet. That’s why shingles must be installed as soon as felt underlayment is laid down over the decking. 

On the other hand, synthetic underlayment repels water and even holds roofing nails better. It’s also safer to work on as your roofing contractor installs the rest of your roofing components and materials. 

Because synthetic underlayment is made to be non-skid, you don’t have to worry about tearing or crew members slipping as they finish your roof.

Which roof underlayment weighs more?

You probably don’t consider the weight of a material an important comparison. However, the weight of your roof underlayment impacts the labor cost of your roof replacement

With that in mind, felt underlayment weighs more than synthetic underlayment. But why does the heavier product add to the labor cost?

Because felt roof underlayment is heavier, it doesn’t have as much material per roll as synthetic roof underlayment. This leads to needing more rolls, which takes more time and manpower to get it up the ladder for installation.   

While this won’t add a lot to the labor cost, it’s just something to keep in mind when deciding which roof underlayment to choose. 

Which roof underlayment costs more?

Cost is the biggest concern for most homeowners going through the roof replacement process. While your roof underlayment will be wrapped into the total cost per square of your new roof, the two types have different price points. 

Unfortunately, I can’t give you exact pricing because of the constant fluctuation of material prices in the roofing industry. With that in mind, synthetic roof underlayment is more expensive than felt roof underlayment. 

Just know that the cost difference between the two isn’t honestly that far apart. Roof underlayment, in general, doesn’t necessarily have a huge impact on the overall pricing of a new roof. 

However, considering your budget is still important when deciding which roof underlayment is right for you.

Learn the rest of the important roofing components

By the end of this article, you should know which roof underlayment is right for you. But your roof’s underlayment is just one crucial roofing component that makes up a complete roof system. 

Knowing the rest of the components and materials helps you understand what you’ll pay for when getting a roof replacement. It also ensures you know what must be included in your roof estimate

That’s why I wrote another article breaking down the rest of the roofing components that make up a roof system and their function. 

Since 1990, the team at Bill Ragan Roofing has provided high-quality roofing services to thousands of homeowners in Nashville and surrounding Middle Tennessee areas. We take pride in everything we do and back up our workmanship with a lifetime craftsmanship warranty. 

Check out 9 Materials Included With Your Roof Replacement to learn what you’re paying for when it’s time for a new roof.

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