Commercial, Mixed-Use and Strata Roof Maintenance in Vancouver, B.C.

Types of Roofing Underlayment: How To Choose The Right One

Types of Roofing Underlayment: How To Choose The Right One For Your Home, And More!

Water is the single factor that causes almost 80% of roofing issues. To counter these problems a roofing underlayment is used. If you are a property owner wondering what an underlayment can do for your roof you have come to the right place.

There are namely three types of roofing underlayment Asphalt Saturated Felt, Rubberized Asphalt underlayment, and Non-bitumen synthetic underlayment.

In this article, we discuss what is roofing underlayment, its types, and its need in great detail.

What is an underlayment?

An underlayment, as the name suggests, is a layer of a waterproof thin sheet laid on your roof deck, underneath the roof shingles. It provides smoothness to the roof and protects it from water infiltrations, heat, snow, and other weather conditions. Once the topmost layer of the roof is installed, the underlayment is not at all visible.

Why is underlayment necessary? (Its Advantages)

One of the common questions my clients ask me is why is underlayment necessary? An underlayment is no different from roof shingles, as they both are water resistant. However, what people do not know is that shingles do not prevent 100% water penetration, while a layer of underlayment does.

Here are some major advantages of roofing underlayment:

  • An underlayment makes sure no water reaches the inner layers of the roof. It prevents leaks caused by faulty equipment or extreme weather conditions.
  • Over time shingles bulge due to an uneven frame below. This is called ‘Picture Framing. Underlayment works out the problem of picture framing by providing a smooth layer underneath.
  • When roofing materials age they leave the edges and corners exposed to moisture, An underlayment makes sure all these exposed areas are covered.
  • It aids in increasing the life span of the roof.

Types of roof underlayment:

Roof underlayment’s are commonly made up of synthetic fibre or felt. Originally asphalt saturated felt was the only type of roof underlayment. However, now there are three types namely:

  • Asphalt Saturated Felt
  • Rubberized Asphalt underlayment
  • Non-bitumen synthetic underlayment

Let’s have a close look at each of these underlayment’s along with their pros and cons, so you can decide which one works best for your roof!

Asphalt-Saturated felt:

This is one of the most popular underlayment’s that’s been used in roofing. It’s mainly made up of organic or fiberglass substrates. The organic substrate provides a cellulose base to the roof, which helps in keeping it draught-proof and reduces noise.

To make the felt water resistant, it is saturated in crude oil byproducts like bitumen. This bitumen saturation also helps in making the felt damage resistant. Asphalt-saturated felts usually have two thicknesses:

15 pounds and 30 pounds. The 15 pounds felt can break and get damaged easily, while the 30 pounds ones are thicker and more durable.

Asphalt-saturated felt has been a common choice for residential roofing.



  • It is extremely cheap, hence making it the most affordable type of underlayment.


  • It provides an excellent barrier that prevents seepage and leaks and is very reliable for protection purposes.


  • ASTM D226 is a standard specification used for Asphalt-Saturated Organic felt, it is highly water resistant.



  • Asphalt saturated underlayment is made up of volatile compounds. Due to constant sun exposure, these compounds fade away making the felt get thinner. This makes the felt weak and prone to water damage.


  • Also, these underlayment’s backfire if a poor quality felt is used. They absorb moisture making the deck even weaker.


  • UV (ultraviolet) rays from the sun when absorbed by this type of underlayment, deteriorate it, making the roof fragile.

Rubberized Asphalt Underlayment:

Rubberized Asphalt Underlayment also known as the self-adhering underlayment is a top-quality roofing underlayment. This type of felt has a gummy layer that sticks directly to the deck of your roof.

As the name suggests, it’s mainly made up of rubber polymer and asphalt. This composition makes it best for protection against extreme temperatures and harsh weather conditions. If the underlayment gets damaged then it can be fixed easily.

Its incredible roof protecting and leakage-preventing properties make rubberized asphalt underlayment of the most expensive underlayment’s available.



  • Rubberized asphalt underlayment is the only type that guarantees a 100% waterproof seal.


  • Due to its adhesive surface, it is easy to install.


  • Installation cost is low.


  • It doesn’t deteriorate because of constant sun exposure as it’s resistant to UV rays.


  • It has maximum durability and minor damages can be easily repaired with tape.



  • It is the most expensive out of other underlayment’s.


  • A professional and skilled roofer is needed to install this kind of underlayment.

Non-bitumen Synthetic Underlayment:

Non-bitumen synthetic underlayment doesn’t contain asphalt in it, instead, it comprises polyethylene or polypropylene polymers. This makes the underlayment not only water resistant but also exceptionally fire and wind-resistant.


This type of underlayment is getting more popular among roofers now because it’s a good alternative to asphalt saturated felt and also cheaper than rubberized asphalt underlayment.



  • Non-bitumen synthetic underlayment is heat resistant and won’t deteriorate due to sun exposure.


  • It’s long-lasting and durable.


  • It is easier to install as the synthetic material used is lighter in weight and more resilient.


  • This type of underlayment is also highly resistant to UV rays and suitable for harsh summers.


  • One of the best things about synthetic underlayment is that it’s recyclable.


  • The installation cost is comparatively less.



  • It is more expensive compared to asphalt felt.


  • Also, requires professional roofers to install this kind of underlayment,

How to choose a Roofing Underlayment perfect for your roof?

After knowing the pros and cons each of roofing underlayment, you can pick the one best for your house. Regardless, there are some other factors you need to consider, before finalizing your pick.

  1. Type of your roofing system:

The type of roof you have plays a crucial role in deciding which underlayment you must choose. For example; Synthetic underlayment works best for a metal roof, as it’s heat resistant. A metal roof is a heat conductor. It expands and contracts continuously given the amount of heat it is subjected to. Likewise, Asphalt underlayment goes well with an asphalt shingle roof.

  1. Climate:

Climate also needs to be taken into consideration. Pick an underlayment base on you’re the weather of your region. For example; Asphalt-saturated felts can rot in extremely humid conditions but synthetic underlayment is suitable for such weather.

  1. Budget:

Different types of roofing underlayment have different costs. Your budget plays an important role in the type and quality of underlayment you pick.

A combination of all the above 3 points will help you select the perfect roofing underlayment for your home. However, it is best to consult a professional roofer before you take the final decision.


I hope this article answers all your questions about Roofing Underlayment. However, if you have any more questions or doubts about this product, feel free to comment down below. Also, if you need a reliable roofing team to take a look at your roof contact us TODAY!

LeakStop is a one-stop destination to meet your roofing-related requirements. We offer roof repair, replacement, maintenance, and inspection services all over GVRD (Greater Vancouver Regional District).

We offer a free inspection to first-time clients. Connect with us TODAY at 1 866 777 0084 for immediate assistance!

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