What is Roof Underlayment? - Roofing Underlayment

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What is Roof Underlayment?

Most homeowners recognize the importance of their roofs and the attention that should be given to roof maintenance and repair services. If a roof is old or damaged, it may amount to dangerous roof leaks or stripped roofing material. This can cause severe damage to the internal structure of your home, costing hundreds, or even thousands, of dollars in repair costs. This is where roof underlayment comes in. You may ask: what goes under shingles? Equipped to act as a protective shield, shingle underlayment reinforces the barrier against outside elements such as rain, debris, and ice. Roofing underlayment installation makes a big difference in the strength of your roofing system.

roof underlayment

What is Roofing Underlayment? 

Roofing underlayment is a type of water-resistant material installed directly onto the roof deck below roofing shingles. Because it’s installed before the roofing material, it won’t be visible after the roof replacement is completed. While roof underlayment is not mandatory, it adds another layer of protection that works well to protect your roof from leaks, harsh weather, and deterioration. 

Types of Roofing Underlayment

Asphalt-Saturated Felt

Asphalt-saturated felt is made of polyester, asphalt, and plant fibers to create a flexible, water-resistant base. Also called “tar paper” or “felt paper,” this was the most common type of roofing underlayment until synthetic underlayment became popular about 15 years ago. Asphalt-saturated felt is ideal for roofs with steep slopes where water can easily drain. It can be found in different thicknesses, which will determine its resistance to water damage. 


Self-adhered roof underlayment is constructed from asphalt and rubber polymers, which makes it a water-resistant material. Also called rubberized asphalt, this material comes with a sticky back for easy adhesive onto the roof deck. This also helps to create a seal between the underlayment and roof deck. It’s specifically designed to offer extra protection where water commonly causes damage on roof decks. These areas may include chimneys, eaves, valleys, and vents. This material is typically the most expensive type of roof underlayment, because of the polymers that allow for water-proofing. 


Synthetic roof underlayment is a popular choice for roofers. It consists of a synthetic base saturated with asphalt and fiberglass. Non-bitumen synthetic underlayment can also be found, which is flexible and waterproof. A benefit to synthetic roof underlayment is how lightweight it is. It’s also resistant to mold, UV rays, and is long lasting. It can be more expensive and takes time to install, but you may find that synthetic material is well worth the investment.

Roof Repair, Service, & Replacement

Serving GA, TN, FL, and AL

Why Do I Need Roof Underlayment?

Roof underlayment is not 100% required, but we absolutely recommend it. The extra protection it brings to your roof may just save you from invasive roof damage and high repair costs. Roofing underlayment will strongly protect against moisture, which can get trapped underneath shingles and cause leaks and mold. If you have shingles blown off the roof during a storm, the roofing underlayment will protect the decking from ice, snow, rain, and other elements. 

Roof underlayment is created to be water-resistant and seal the deck from any type of moisture. Shingle underlayment can also help with fire safety and may allow you to meet Class A fire ratings. Another benefit to underlayment for roofs is the smooth look it creates. Most roof decks are uneven, and underlayment provides a uniform base for shingles to attach to. While roofing underlayment is an additional expense, we’ve found time and time again that it’s well worth the investment. 

roof pitch

We Install Roof Underlayment! 

Perimeter Roofing serves GA, TN, FL, and AL with roof replacement, repair, and maintenance! If your roof needs to be serviced, we’re the best team for the job. We’ve studied the best methods for roofing underlayment installation and are committed to ensuring your roof is protecting your home well. Interested in learning more? Schedule a free consultation with us today!

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