Roofing underlayment is a protective layer that enforces your roof by providing a waterproof layer between your roof sheathing and shingles. While you can’t see this vital part of your roofing system, it’s crucial in keeping your home comfortable and dry by protecting it from leaks and strong weather, like hurricanes.

So, what are the other reasons why you need strong roofing underlayment, and what types of roofing underlayment can you choose from to reinforce your roof? Keep reading to learn everything you need to know about roofing underlayment.

    The Different Types of Roofing Underlayment

    roofer tears off protective cover of underlayment on a new roof
    Image Source: Canva

    Synthetic Roofing Underlayment

    Today, most professional roofers will use completely synthetic underlayment or non-bitumen synthetic underlayment. The synthetic basemat of this type of roofing underlayment is saturated in asphalt, giving it a high amount of water resistance. Then, fiberglass is added to the roofing material, further increasing tear resistance and stability.

    More expensive, high-quality synthetic underlayment also has coarse or scrim woven material reinforcement, which gives the material slip resistance even if it’s wet. The non-bitumen synthetic roofing material is extra flexible, sturdy, waterproof, and mold-resistant. It’s much lighter than rubberized asphalt underlayment, making it a more suitable underlayment for concrete tile roofs or other types of roofs made out of heavier material. Another benefit of synthetic underlayment is that it’s long-lasting and protects against fungus and UV exposure.

    Asphalt-Saturated Felt Underlayment

    Asphalt-saturated felt roofing underlayment was the most popular choice until around 15 years ago when synthetic roofing material became more popular.

    Asphalt-saturated felt roofing is also known as “roofing felt,” “felt paper,” or “tar paper.” This roofing underlayment is made of different polyester blends, natural plant fibers (cellulose), and asphalt (bitumen). It’s a great roofing material because it’s flexible and covered in asphalt, making it ideal as underlayment for metal roofs and for water resistance. Most roofing contractors will fasten asphalt-saturated felt roofing with staples, fasteners, or the roof deck with plastic caps.

    Felt underlayment comes in two thicknesses: 15-pound and 30-pound. The 30-pound felt is much more damage-resistant during installation and has more longevity, making it a better choice in many cases. However, 30-pound felt underlayment is less flexible, making it challenging to install.

    Another downside of this type of roofing material and one of the differences between synthetic for underlayment and felt is that asphalt-saturated felt is not waterproof, making it an ideal choice for steeply sloped roofs because water can run off the surface. Flat roofs should not use asphalt-saturated felt underlayment because the water will remain on the roof and eventually penetrate the roof decking.

    Rubberized Asphalt Underlayment

    Consider a rubberized asphalt underlayment if you live in an area with extreme temperatures. It’s waterproof, UV ray resistant, and flexible. The biggest downside is that it’s more expensive and heavier than other options. However, the added protection is crucial for certain climates.

    Rubberized asphalt underlayment is highly waterproof and has a self-adhesive back with a protective membrane that creates a tight seal on the roof. It should be installed at the roof’s eaves to keep water from damaging the roof deck’s edges. It can also be added to low areas, like roof valleys and protrusions, to reduce the risk of leaks. Benefits of Roofing Underlayment

    Benefits of Roofing Underlayment

    roofer nails down an underlayment on a new roof
    Image Source: Canva

    Roofing underlayment can benefit homeowners greatly by providing a strong roof covering and a layer of protection against high wind and water. Here are some of the other significant benefits of installing underlayment materials on your roof:

    Adhering to Building Codes

    Depending on where you live, it may be mandatory to have a certain type of roofing underlayment or amount of underlayment material to meet the local building codes. Consult with your roofing contractor about your local and federal construction regulations.

    Fire Safety

    Your roof shingles alone don’t meet Class A fire ratings, which puts you and your family at risk without a roof underlayment installed. Roofing underlayment that meets industry standards and building codes and matches overlying shingles will help your roof meet these crucial Class A fire rating requirements.

    Moisture Barrier & Water and Ice Damage

    Rain and snow can become trapped under your roof shingles without a roofing underlayment, causing water damage. If the water becomes trapped under your shingles regularly, it can cause mold, wood rot, leaks, and irreversible damage.

    Ice and snow dams can also form on your roof, straining the structure and putting your roof at risk of water damage, mold, and leaks. A water-resistant underlayment creates a seal on your roof frame, ensuring water drains off your roof and doesn’t collect and seep through.

    As a result, roofing underlayment gives crucial protection that your shingles can’t provide on their own.

    A Uniform Surface for Your Roof

    Many roofing decks don’t lie flat or straight, making creating a uniform look for your shingles challenging. However, a roof underlayment can create a uniform, smooth surface for your shingles to be installed on top. Felt or synthetic roofing underlayment creates a layer on your roof that the roofer can install the shingles on top of and make a “picture framing” effect that is polished instead of patchy or uneven.

    Weather Protection

    The most obvious benefit of roofing underlayment is the weather protection it provides your roof. Shingles are the biggest line of defense on your roof because they’re designed to decrease water prevention, withstand strong winds, and reflect UV rays, giving your roof added protection. Unfortunately, strong winds can lift overlapping shingles and blow them off your roof, opening your roof up to water intrusion and damage.

    Even if all of your shingles are in place, water can sometimes still sneak under shingles, so a roof underlayment gives added protection to keep rain, ice, and snow from rooting your roof deck and causing leaks.

    To further protect your roof and keep it in good condition, it is advisable to consider signing up for a reliable home protection plan.

    Final Thoughts

    Roofing underlayment is critical to protecting your entire roof from bad weather conditions and weather events, like rainstorms, dust storms, and hurricanes. Speak with your roofing contractor about the different underlayment types available to you and which type of underlayment will best fit your roof. The weather in your area, typical temperatures, and the slope of your roof all play a massive role in which roofing product you should go with, so take your time and consider all your options. A heavy-duty underlayment can save you time, money, and frustration over the years by reducing roof repair costs, preventing ice dams, and decreasing water infiltration.

    Editorial Contributors
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    Amy DeYoung


    Amy DeYoung has a passion for educating and motivating homeowners to improve their lives through home improvement projects and preventative measures. She is a content writer and editor specializing in pest control, moving, window, and lawn/gardening content for Today’s Homeowner. Amy utilizes her own experience within the pest control and real estate industry to educate readers. She studied business, communications, and writing at Arizona State University.

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    Lora Novak

    Senior Editor

    Lora Novak meticulously proofreads and edits all commercial content for Today’s Homeowner to guarantee that it contains the most up-to-date information. Lora brings over 12 years of writing, editing, and digital marketing expertise. She’s worked on thousands of articles related to heating, air conditioning, ventilation, roofing, plumbing, lawn/garden, pest control, insurance, and other general homeownership topics.

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