What Is Roof Underlayment and Why Do You Need It?

When it comes to your home’s roof, numerous components work together to create a roofing system that protects your home. A crucial element that often goes unnoticed is the roof underlayment. So what is roof underlayment? 

In this article, we’ll delve into the world of roof underlayment, shedding light on what it is, the different types available, and explain why it plays a vital role in safeguarding your roof. 

If you’re a homeowner seeking to further your understanding of your home’s roofing system, read on to discover the significance of roof underlayment and why your roofing system needs it. We’ll also provide insight into how you can extend the longevity of your roof.

What Is Roof Underlayment?

Since roof underlayment offers no aesthetic appeal, it isn’t usually at the top of the list when homeowners consider roofing projects. Still, it plays a critical role in your roofing system. 

Roof underlayment is a layer of material installed between primary roofing materials like the shingles and the roof deck.

There are different kinds of roof underlayment, each having its own advantages and disadvantages. Some are more durable and protect better against water infiltration and extreme weather, while others have more of a reputation for their eco-friendliness or cost-effectiveness.

Why is roofing underlayment important? 

Underlayment provides an additional protective barrier that enhances your roof’s overall performance and longevity. 

Roof underlayment is one of several roofing components that bolsters defense against water infiltration. Even with a sturdy, well-laid roofing material, water sometimes penetrates through gaps, seams, or damaged sections. 

Underlayment prevents water from reaching vulnerable areas of the roof deck that can potentially cause leaks and water damage inside your home.

But, waterproofing capabilities aren’t the only reason roof underlayment is used. It also plays a crucial role in preventing roofing material from sticking to the roof deck. 

Without roof underlayment, the material would likely adhere to the deck because of the moisture levels and temperature changes that cause it to expand, contract, and shift over time. If this were to happen, it could compromise the integrity of your roofing components and make repairs and replacements much more challenging and costly.

Roof underlayment can also reduce noise transmission. Underlayment acts as a sound barrier that absorbs and softens the noise from rainfall, hail, or other external disturbances, resulting in a quieter living environment.

Underlayment materials also have insulation properties that contribute to energy efficiency. Roof underlayment can help minimize heat transfer, keeping your home cooler in hot weather and reducing the cooling system’s workload. 

Similarly, underlayment helps retain the heat inside your home during cooler weather, improving comfort and potentially reducing heating costs.

Finally, roof underlayment also adds to the overall roof structure’s strength and stability since it helps evenly distribute the weight of the roofing materials across the roof deck. This reduces the risk of sagging or structural damage. 

For this factor alone, roofing underlayment is crucial in helping your roof withstand extreme weather conditions such as high winds, hurricanes, and heavy snowfall. 

What Are the Types of Roofing Underlayment Materials?

Roofing underlayment comes in various materials that have their own unique characteristics and advantages. We’ll review the three main categories of roofing underlayment materials so you can decide which is best for your roof.

1. Asphalt-saturated felt: This traditional underlayment is utilized the most by homeowners and roofers. It is composed of organic or fiberglass fibers combined with asphalt. 

• Pros:
  • Affordability
  • Ease of installation
  • Widely compatible with most roofing materials

• Cons:
  • Relatively heavy, which can make transportation challenging
  • Potentially prone to tearing or wrinkling during installation, compromising its effectiveness
  • Tends to absorb moisture over time, reducing its longevity

2. Synthetic underlayment: As a newer and more advanced option, synthetic underlayment has gained popularity in the roofing industry and is the go-to choice today.

It is typically made from polypropylene or polyester fibers and may have various coatings or additives to enhance its performance.

• Pros:
  • Lightweight and easier to handle
  • Ease of installation
  • Highly durable
  • Water and fire-resistant
  • Breathable and allows moisture to escape, minimizing the growth of mold and rot

• Cons:
  • Higher cost compared to asphalt felt
  • Use may be prohibited by some building codes
  • Material degrades easily in hot and humid climates
  • Difficult to remove for repairs and replacements

3. Rubberized asphalt underlayment: This type of underlayment combines the benefits of asphalt and synthetic materials. It is typically made from a combination of asphalt and rubber polymers.

• Pros:
  • Excellent waterproofing properties
  • Enhanced durability
  • Flexible
  • Can withstand extreme temperatures
  • Resists UV radiation
  • Helps ensure a longer lifespan for your roof
• Cons:
  • The most expensive of the three main types of roofing underlayment materials
  • More prone to UV damage
  • Tears easily during installation

Asphalt-felt underlayment is more popular, perhaps due to its affordability. But synthetic underlayment provides enhanced durability and water and fire damage resistance. 

On the other hand, rubberized asphalt underlayment combines the benefits of both asphalt and synthetic materials offering superior waterproofing and longevity. 

How to Choose the Best Underlayment for Your Roof

When choosing the best underlayment for your roof, consider the type of roofing material you have, your climate, the pitch of your roof, and how much you want to spend. Take the following into consideration to make an informed decision:

1. Type of roofing material: Different roofing materials have specific compatibility considerations for underlayment. For instance, asphalt shingles work well with asphalt felt or synthetic underlayment. Conversely, metal roofs do well with a synthetic or rubberized asphalt underlayment. 
2. Climate and weather conditions: It’s not surprising that the climate in your area plays a significant role in underlayment selection. If you’re in a region with heavy rainfall or snowfall, you’ll need an underlayment with excellent waterproofing properties. Alternatively, if you experience high winds or hurricanes in your area, look for underlayments with enhanced strength and wind resistance. Additionally, you’ll need to consider the temperature variations and UV exposure as some underlayments are designed to withstand extreme fluctuations better. 
3. Roof pitch: The pitch or slope of your roof affects water runoff and the potential for moisture accumulation. Steeper roofs require underlayments with better water-shedding capabilities to avert water infiltration. Lower slope roofs benefit from underlayments that provide superior waterproofing. 
4. Budget considerations: When budgeting for your roofing project, allocate a portion for underlayment. Different underlayment materials have varying costs. The traditional asphalt-felt underlayment is the least expensive, while synthetic and rubberized underlayments often come at a higher price point due to their advanced features and durability. The important thing to remember is to get the level of protection you need for your roof and home. 

Consider the following comparison table to assist you in the decision-making process. It showcases the different features and benefits of each type of underlayment material based on various scenarios.

Assess your roofing material, the climate, your roof’s pitch, and your budget to determine the underlayment that provides the best combination of performance, longevity, and affordability for your roof.

How to Maintain and Protect Your Roof Underlayment

Once your roof underlayment is installed, proper maintenance and protection are necessary to ensure its longevity and effectiveness. You can prevent common issues and preserve the integrity of your underlayment by following a few tips. 

First, let’s go over a couple of factors you should be aware of:

1. Breathability and moisture resistance: Synthetic underlayment is breathable, allowing moisture to escape while protecting against water infiltration. 

Conversely, underlayment with a vapor barrier is intended to be impermeable to moisture. 

Understanding the differences between these two types of underlayment will help you manage water-related issues.

2. Risk of mold growth, wood rot, and ice dams: Inadequate moisture management can lead to mold growth, wood rot, and the formation of ice dams in the attic or roof deck.

Improper ventilation and insulation can contribute to these issues because trapped moisture creates an environment for mold growth. Mold can compromise the structural integrity of your roof. 

On the other hand, ice dams can form when snow melts on the warmer areas of your roof and then refreezes near the colder edges. This can lead to water infiltration and potential damage.

Preventing Problems With Your Roof and Roof Underlayment

To prevent or treat the issues mentioned above, consider the following: 

• Proper ventilation: Ensure your attic has adequate ventilation to allow air to circulate effectively. Doing so will help regulate your attic’s temperature and humidity levels, reducing the risk of moisture buildup.
• Improve insulation: To help maintain consistent temperature levels in your attic, it must be adequately insulated. This will help minimize the potential for condensation to form and prevent other moisture-related issues.
• Maintain proper drainage: It’s best to do regular maintenance on gutters and downspouts so they’re clean and free of debris, allowing for proper water drainage away from the roof.
• Regularly perform inspections: To help prevent damage, be sure to conduct routine inspections of your roof, underlayment, and attic space for any signs of mold, wood rot, or ice dams. If any issues are spotted, address them promptly to prevent further damage. 

If you take preventative measures and address any issues as soon as they arise, you’ll enjoy the functionality of your roof underlayment for years to come. Taking care of your underlayment by doing regular inspections and maintenance will go a long way in protecting and preserving the overall integrity of your roofing system.

Final Thoughts

By now, we’ve comprehensively addressed a common question by homeowners: What is a roof underlayment?

Roof underlayment is essential for a durable, high-performing roof. It acts as a secondary defense against water infiltration, aids in noise reduction, prevents roofing material from sticking to the deck, enhances insulation, and adds strength to the overall roof structure. 

Since roofing underlayment plays such an integral part in your roofing system, choosing the best underlayment for your roof should be carefully considered. Factor in everything from your roofing material, your region’s climate, your roof’s pitch, and your budget. 

You’ll also need to have a thorough understanding of the three main types of underlayment available because felt underlayment, synthetic underlayment, and rubberized asphalt underlayment each have their own advantages and drawbacks. 

Regardless of the type of underlayment you choose, you should conduct regular roof inspections and act quickly to address issues. If you focus on moisture management and follow our guidelines, you’ll safeguard your entire roofing system and gain peace of mind for years to come.
It also pays to get the help of a qualified roofing expert to perform inspections and evaluate any potential issues. All Star Home is a premier roofing company that serves homeowners nationwide. Contact us for your free estimate and consultation.