3 Types Roofing Underlayment: How To Choose the Best Roof Underlayment?

When most people think about roofing, they often forget the underlayment. However, this is an essential roofing component that you cannot afford to ignore.

While your asphalt or sheet covering will protect your roof from the elements, there is still a possibility that moisture and heat will still penetrate. The extra layer of protection insulates the roof and keeps the moisture and heat from seeping through to the house.

There are three common types of roof underlayment. Choosing the right one for your roof will eliminate the need for many repairs, and it will lengthen the lifespan of your roof. Below, we examine each type to help you make an informed choice.

Asphalt-Saturated Felt Roof Underlayment

The underlayment is made from either fiberglass or organic felt that is saturated with asphalt. However, the organic felt version is more common. The industry refers to it as organic since it comes with a cellulose base.

Asphalt-Saturated Felt

This felt is popular for good reason. It is cheap and easy to install. However, this is the least durable option.

It wrinkles and tears quicker and is not entirely waterproof. Moreover, it tends to deteriorate with exposure to direct UV. However, all this will depend on the thickness and quality of the underlayment. For instance, a 30-pound thick option will be more durable and water-resistant than a 15-pound underlayment.

Asphalt-saturated felt is best suited for steep-sloped roofs because it tends to absorb water. However, you can still install them in a low-sloped roof of, say, 2:12, provided the courses have an overlap of not less than 19 inches.


  • Cheap
  • Easy to install


  • Least durable
  • Least water resistance

Rubberized Asphalt Roof Underlayment

Rubberized asphalt is a peel and stick roof underlayment with a self-adhering surface protected by a peel-off membrane. It is made from materials with rubber-like qualities.

The rubber polymers are impervious to water which makes the underlayment 100% waterproof. Also, their elastic nature gives them self-sealing abilities, enabling them to seal the spaces between the nails and fasteners.

Rubberized Asphalt Roof Underlayment

Rubberized asphalt is ideal for colder and snowy regions due to its waterproof nature. But it also performs well in high temperatures. If rated 250° F or higher, you can even install it under metal roofing. Of the three, this is the most expensive option owing to the high cost of the materials. It is also heavy and labor-intensive, especially in steep-sloped roofs. That makes it the least popular roof underlayment.


  • 100% waterproof
  • Self-sealing abilities


  • Expensive
  • Labor intensive

Non-Bitumen Synthetic Roof Underlayment

Synthetic is the latest type of roof underlayment and is quickly becoming the go-to choice for many people. The underlayment is made by mixing polymers with polypropylene or polyethylene. The manufacturers also incorporate fiberglass for added strength.

Non-Bitumen Synthetic Roof Underlayment

This underlayment is very durable since the thermoplastic polymers are quite resistant to UV penetration, tear, and fungal growth. They also have a high tolerance to high temperatures. Of the three, non-bitumen synthetic has the longest lifespan.

Furthermore, the underlayment comes with an anti-slip feature that makes it safer to walk on the roof, even on steeper slopes. Their light nature also makes them easier to install and appropriate for all types of slopes. However, they may require cap nail fastening, which is likely to increase labor costs and heighten the risk of water intrusion if damaged.


  • Light
  • Longest lifespan
  • Anti-slip feature
  • Ideal for all slopes


  • Nail fastening increases labor cost
  • Fasteners increase the risk of water intrusion

What is the Importance Factors of Roof underlayment?

Installing an underlayment between the top layer and roof deck can be beneficial. It can enhance the roof’s durability, improve its lifespan and lower your energy bills. Here are some of the benefits of installing a roof underlayment.

Backup Protection

Although shingles or tiles will protect the roof, they can get damaged over time. In such cases, the underlayment can work as backup protection.

Moisture and Heat Barrier

The top layer will guard the roof against the vagaries of weather, but moisture and heat can still find a way to seep through. An underlayment can act as an extra barrier, thus preventing the two from permeating into the building.

Protection against Snow and Water Damage

If you live in a region that experiences excess rain, snow, or ice, the extreme weather can take a toll on your roof. That may lead to leaks and water damage. The extra layer underneath can act as a barrier, preventing the water from getting through.

Energy Efficiency

As stated above, an underlayment gives the roof much-needed insulation. It prevents air and heat from permeating through into the building, thus saving you a lot of money in energy bills.

Do all Types of Roofs Need an Underlayment?

An Underlayment may not be an absolute necessity in all cases. However, it can still be beneficial. It may not protect the roof’s structural integrity as in metal roofing, but it will act as a moisture barrier. Moreover, it can prevent condensation.

How To Choose is the Best Roofing Underlayment?

When choosing the best underlayment for your roof, you have to consider a variety of factors. They include the following:

Type of Roofing Material

Ensure the type of underlayment you install is best suited for your roof. For instance, shingles will work well with asphalt-felt. Also, your underlayment needs to have a high heat resistance if you have a metal roof.


The type of weather is also an important consideration. Some underlayment may not last as long in certain weather conditions. For instance, asphalt-felt may not be the best choice if you live in an area that experiences heavy snow or rain due to its poor water resistance.

Type of Slope

The type of slope should also be a guiding factor. For example, asphalt-felt is the least suitable underlayment for low-sloped roofs. On the other hand, non-bitumen synthetic will work with all types of slopes.


Going for the cheapest option available is not always the best decision. But don't spend more than you can afford either. The budget should be the last consideration you make once you determine what option best suits your situation. The trick is finding that elusive balance between price and performance.


Underlayment is an essential part of roofing that deserves as much attention as the other aspects of roofing. While it is not a mandatory addition, it comes with many benefits that cannot be ignored. However, the three options available are different and will serve different needs.

If you want the cheapest option available, asphalt-felt could work as long as the weather is conducive. Rubberized asphalt will give you the best water resistance, but it is the most expensive option available. 

If you are looking for the best balance between price and performance, non-bitumen synthetic is your best bet. However, your ultimate choice should depend on your unique needs.

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