Our Guide to Roof Underlayment Types: What You Should Know

Our Guide to Roof Underlayment Types: What You Should Know

Your roof plays an essential role in protecting you and your household from the elements. Although it may not be the most prominent part of your home’s façade, it is crucial to pay attention to it and maintain it to remain sturdy and keep you safe from the wind, rain, snow, and other weather conditions.

Underlayment roof

Part of maintaining your roof involves understanding the whole roof system, which includes the roof underlayment. Though you may not have heard of it, it does a lot to protect you every day. Here’s what you need to know about roof underlayment and the different types:

This Article Contains

What is Roof Underlayment?

Roof underlayment is a barrier material installed onto your roof deck with water-resistant or waterproof properties, defending your roof and home from moisture. It also adds another layer of protection from severe weather conditions like snow, wind, rain, and hail.

Why is Roof Underlayment Important?

Depending on the climate, a roof underlayment isn’t always necessary. However, since Boise experiences wet weather conditions, it’s crucial to have a moisture barrier to protect your home from water damage.

While shingles offer some protection to your home, they’re the first line of defense, which means they need more layers to provide your home with the comprehensive cover it needs from the elements. They do a great job of reflecting the sun’s rays, blocking the wind, and defending against precipitation. However, they aren’t sealed at all corners and they overlap, which means strong enough winds can lift them, making them prone to tearing off or get infiltrated by rain and heavy winds. They can also deteriorate and become brittle over time, which is why a roof underlayment is a crucial component of your roof.

What are the Types of Roof Underlayment?

There are three types of roof underlayment used:

Asphalt-Saturated Felt

This type of roof underlayment is water-resistant and is often referred to as felt paper or tar paper. It is made from different blends of cellulose or natural plant fibers, polyester, bitumen, or asphalt. Asphalt-saturated felt was the preferred choice until almost two decades ago, though it remains to be an excellent shingle underlayment. It started fading in popularity as synthetic products entered the market. 

Asphalt-saturated felt has a base mat or a flexible base layer that is soaked with asphalt to make it water-resistant. The roofer must apply it across the entire roof deck and may add a waterproof underlayment.

One of the benefits of this underlayment type is that it has multiple thickness options with different resistances to damage and weather exposure, allowing you to choose what you need for your home. For instance, a 30-pound asphalt-saturated felt can protect the roof more extensively against hail, wind, snow, and rain. It’s also less expensive than other materials. However, it can be heavy, especially when it has enough layers to work effectively against harsh weather conditions. Due to its weight, it can be more challenging to install than other options. Additionally, it is susceptible to wrinkling and cracking when exposed to cold weather.

Synthetic Underlayment

Synthetic underlayment, known as non-bitumen synthetic underlayment, is also water-resistant, which is why most roofing professionals prefer installing it. The base mat is saturated in asphalt with a dose of fiberglass, giving it exceptional tear resistance and stability. It is also meant to be used across the entire roof deck and is sometimes coupled with waterproof products.

However, a disadvantage of synthetic underlayment is that it is often more expensive than asphalt-saturated felt. It also needs more tools and skills to install correctly, so it’s best left to a Raleigh roofing contractor. Still, it’s much lighter than asphalt-saturated felt, durable even when exposed to high winds, and does not absorb moisture, making it resistant to mold and fungal growth. It also doesn’t break down as quickly as other underlayment types, which explains why it is the top choice of roofing contractors.

Rubberized Asphalt

Rubberized Asphalt is waterproof, making it more expensive than the other roof underlayment types. This quality is attributed to its higher concentrations of asphalt and rubber polymers, making it an excellent choice for houses in especially wet climates.

This underlayment type has an adhesive back with a protective membrane that must be removed before installing it. The unique backing provides a waterproof seal between the roof deck and the underlayment, which is especially useful for protecting the eaves of a roof during harsh winter weather.

Additionally, the underlayment protects the roof deck’s edge from water damage. That is why rubberized asphalt roof underlayment is incredibly helpful when added at valleys and roof protrusions, as these areas experience high amounts of moisture. They’re also more heat and cold-resistant than asphalt-saturated felt and last longer. Its main drawback is that it is much more expensive upfront compared to the other roof underlayment types. However, you’ll save up more money in the long run since it will extend your roof’s lifespan and prevent frequent repairs, which can quickly add up.


Water-resistant roof underlayment adds much-needed protection to your home and is often enough for most roofs. It can shield your home from severe water damage and other hazards. Given the occurrence of ice dams and high winds in Boise during the winter, you may want to invest in a waterproof underlayment, which will give you another line of defense and help keep your home in good shape regardless of the weather. By installing roof underlayments at your eaves, valleys, protrusions, and low-slope roof surfaces, you’ll have a sturdy roof that does an excellent job of keeping you safe and secure throughout the year.

Southern Premier Roofing is a Raleigh roofing company specializing in roofing, siding, and gutter services for both commercial and residential projects in these locations Raleigh, Charlotte, and Fayetteville, NC, as well as Boise ID. From east to west, we provide fair and honest pricing along with outstanding project results to demonstrate our passion for our customers’ property and guarantee their satisfaction with our work. Whether you need a roof replacement, repair, or an overall roof inspection, be sure to contact us today!

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