Roof underlayment is a crucial component of roofing systems, acting as a protective barrier between the roof deck and the shingles. It helps prevent moisture infiltration and enhances the roof’s overall durability.
Various types of underlayment, including asphalt-saturated felt, rubberized asphalt, and synthetic options, offer distinct advantages and disadvantages. Understanding these differences is essential for homeowners and contractors to make informed decisions that align with their specific roofing needs and local climate conditions.
Types of Roof Underlayment
When it comes to roof underlayment, three primary types are commonly used: asphalt-saturated felt, rubberized asphalt, and synthetic underlayment.
- Asphalt-Saturated Felt is a traditional choice made from a combination of asphalt and natural or synthetic materials. It provides basic water resistance and protection but can be prone to tearing and becoming less effective over time, especially in extreme weather conditions.
- Rubberized Asphalt offers superior waterproofing thanks to its high asphalt content and additional rubber polymers. This type of underlayment is highly durable, provides a strong barrier against leaks, and is often self-adhering, making installation easier. It’s ideal for areas prone to heavy rain or ice.
- Synthetic Underlayment is a modern option made from lightweight polymers. It’s highly durable, tear-resistant, and provides excellent water and moisture protection. It’s also UV-resistant, making it an excellent choice for long-term exposure during installation delays or in harsher climates.
Asphalt-Saturated Felt
Asphalt-saturated felt is one of the most traditional types of roofing underlayment. Made by saturating a base material, often felt or a fiberglass mat, with asphalt, it has been a reliable choice for decades.
Although newer options like synthetic underlayment are gaining popularity, asphalt-saturated felt remains a practical and budget-friendly choice for many roofing applications. Here’s a closer look at its characteristics, advantages, and disadvantages.
Characteristics
Asphalt-saturated felt is available in different thicknesses, most commonly 15-pound and 30-pound varieties. The pound rating refers to the weight of the felt per 100 square feet, with 30-pound felt being thicker, more durable, and typically used for steeper roofs or harsher climates.
One of the key characteristics of asphalt-saturated felt is its ability to provide a secondary barrier against water and moisture. In the event that shingles are damaged or improperly installed, the felt serves as a protective layer to help prevent leaks. It is usually installed in overlapping layers, creating a seamless barrier.
The material is relatively flexible and can conform to irregular surfaces, making it easier to install on roofs with more complex structures. However, it can become brittle in cold weather, making installation more difficult in such conditions. The felt is also somewhat breathable, allowing moisture that gets trapped underneath to evaporate, which helps reduce the risk of mold growth.
Advantages
Asphalt-saturated felt has several advantages that have kept it in use for many years despite the rise of synthetic alternatives.
- Affordability: One of the primary reasons homeowners and contractors choose asphalt-saturated felt is its low cost. Compared to other types of underlayment, such as rubberized asphalt or synthetic materials, it offers a budget-friendly option that still provides reliable protection.
- Water Resistance: Asphalt-saturated felt provides a good level of water resistance, making it a suitable option for protecting the roof deck from moisture and rain during the installation process. While not waterproof, it does offer a secondary layer of protection in the event that shingles or tiles are compromised.
- Ease of Availability: This type of underlayment is widely available, and many contractors are familiar with its installation process, making it a convenient choice for residential and even some commercial projects.
- Breathability: Asphalt-saturated felt offers some breathability, which allows moisture that might be trapped under the underlayment to escape. This reduces the likelihood of mold or mildew forming under the roof, helping to preserve the roof’s integrity.
Disadvantages
Despite its advantages, asphalt-saturated felt does come with some notable drawbacks that may cause homeowners or contractors to opt for other types of underlayment, particularly synthetic or rubberized asphalt.
- Durability: One of the main disadvantages of asphalt-saturated felt is its relative lack of durability compared to newer underlayment materials. It can tear more easily during installation, especially in high winds or extreme weather conditions. Once installed, it can degrade over time, becoming brittle and less effective at providing protection.
- Water Absorption: While it is water-resistant, asphalt-saturated felt is not fully waterproof. If it becomes exposed to moisture for an extended period, it can absorb water, leading to potential issues like warping or mold growth. This is especially problematic in areas with heavy rainfall or high humidity.
- Weight: Asphalt-saturated felt is heavier than synthetic underlayment, which can make the installation process more physically demanding. Additionally, the 30-pound variety, while more durable, is significantly heavier and more cumbersome to handle.
- Limited Lifespan: The material tends to have a shorter lifespan compared to synthetic options. Over time, exposure to UV rays, fluctuating temperatures, and moisture can cause asphalt-saturated felt to break down. This means that, in some cases, the underlayment might need to be replaced sooner than synthetic alternatives.
- Installation Challenges: In cold weather, asphalt-saturated felt can become brittle, making it difficult to work with and increasing the risk of tearing. In hot weather, the felt can become sticky and challenging to lay out smoothly. These issues can make installation more time-consuming and labor-intensive.
Rubberized Asphalt Underlayment
Rubberized asphalt underlayment is a high-performance roofing material designed to provide superior waterproofing and protection for roofs in areas prone to heavy rain, snow, or ice. Made with a combination of asphalt and rubber polymers, this type of underlayment offers a more advanced and durable option compared to traditional asphalt-saturated felt. Let’s explore its characteristics, advantages, and disadvantages.
Characteristics
Rubberized asphalt underlayment is highly flexible and durable, even in extreme weather conditions. It often comes with self-adhesive backing, making installation easier and faster as it sticks directly to the roof deck without the need for additional fasteners. The rubber polymers in the underlayment provide excellent elasticity, allowing the material to stretch and conform to the roof surface while maintaining its waterproofing properties.
One standout feature of rubberized asphalt is its complete waterproofing capability. Unlike asphalt-saturated felt, this material forms an airtight seal that prevents water penetration, offering superior protection against leaks and ice damming. It is also designed to withstand high temperatures and UV exposure, making it a reliable long-term solution for various types of roofing systems.
Advantages
Rubberized asphalt underlayment offers several key advantages that make it a popular choice for roofing professionals.
- Superior Waterproofing: The primary benefit of rubberized asphalt underlayment is its exceptional waterproofing capabilities. It creates a fully waterproof barrier, offering maximum protection against leaks, water infiltration, and ice dams.
- Durability: The combination of rubber and asphalt makes this underlayment highly durable and resilient to wear and tear. It can withstand harsh weather conditions, including heavy rain, snow, and high temperatures, without degrading over time.
- Self-Adhesive: Many rubberized asphalt underlayments are self-adhesive, simplifying the installation process. This feature also helps to create a seamless, airtight bond with the roof deck, further enhancing waterproofing and protection.
- Flexibility: The material’s flexibility allows it to accommodate shifts or movements in the roof structure, reducing the risk of cracking or tearing over time.
Disadvantages
Despite its many advantages, rubberized asphalt underlayment has some drawbacks.
- Cost: One of the main disadvantages is its higher cost compared to traditional asphalt-saturated felt or even some synthetic options. The advanced materials and waterproofing capabilities make it a more expensive investment upfront.
- Weight: Rubberized asphalt is heavier than synthetic underlayments, making handling and installation more labor-intensive.
- Installation Sensitivity: While the self-adhesive backing is beneficial, it requires careful installation to avoid misplacement or wrinkling, which can compromise its performance.
Synthetic Underlayment
Synthetic underlayment has become a popular roofing material due to its modern design and enhanced performance over traditional options like asphalt-saturated felt. Made from polymers such as polyethylene or polypropylene, synthetic underlayment provides superior durability, water resistance, and longevity. As roofing systems become more advanced, synthetic underlayment is now commonly used in both residential and commercial roofing projects. Here’s a look at its characteristics, advantages, and disadvantages.
Characteristics
Synthetic underlayment is manufactured from lightweight, high-strength materials, usually polymers, making it incredibly durable and resistant to tearing. It is much lighter than asphalt-saturated felt, allowing for easier handling and faster installation. Despite its lightweight nature, synthetic underlayment is strong enough to withstand harsh environmental conditions, such as extreme temperatures, high winds, and heavy rains.
Another key characteristic of synthetic underlayment is its water resistance. While it isn’t waterproof, it offers better water-shedding capabilities than asphalt-saturated felt. Many synthetic options are treated to resist UV exposure, allowing them to remain uncovered for extended periods without degradation. Additionally, synthetic underlayment is highly slip-resistant, which improves worker safety during installation.
Advantages
Synthetic underlayment offers several advantages that make it an attractive choice for modern roofing systems.
- Durability: The primary advantage of synthetic underlayment is its durability. It resists tearing, punctures, and damage caused by harsh weather, making it more reliable than traditional options like asphalt-saturated felt. It also has a longer lifespan, ensuring lasting protection.
- Lightweight and Easy to Install: Synthetic underlayment is lightweight, which makes it easier to transport and install. Its flexibility allows it to conform to various roof shapes and sizes, reducing installation time and labor costs.
- Water Resistance: Though not fully waterproof, synthetic underlayment offers excellent resistance to water and moisture, helping to protect the roof deck from leaks and damage during and after installation.
- UV Protection: Many synthetic underlayments are designed to withstand UV exposure for several months, which is beneficial if there are delays in roof installation.
Disadvantages
Despite its many advantages, synthetic underlayment also has some drawbacks.
- Higher Cost: One of the main disadvantages of synthetic underlayment is its cost. It is typically more expensive than asphalt-saturated felt due to its advanced materials and improved performance, making it a less budget-friendly option for homeowners.
- Non-Breathable: Unlike asphalt-saturated felt, which has some breathability, synthetic underlayment is often non-breathable. This can trap moisture underneath the roof if not installed properly, potentially leading to mold or mildew issues if ventilation is not adequate.
- Slippery When Wet: Although most synthetic underlayments have slip-resistant coatings, they can still become slippery when wet, posing a safety hazard during installation in rainy or moist conditions.
Comparative Analysis of Underlayment Types
When choosing between asphalt-saturated felt, rubberized asphalt, and synthetic underlayment for roofing, it’s essential to consider factors such as cost, performance, installation, and longevity. Here’s a comparative analysis of these three options:
A. Cost Comparison
Asphalt-saturated felt is the most affordable of the three, making it a common choice for budget-conscious projects. Rubberized asphalt is the most expensive due to its superior waterproofing capabilities, while synthetic underlayment falls in the middle, offering a balance between performance and cost.
B. Performance in Different Weather Conditions
Rubberized asphalt excels in extreme weather, offering excellent waterproofing and resistance to ice dams. Synthetic underlayment is highly resistant to tearing and performs well in both hot and cold climates. Asphalt-saturated felt provides decent protection but can absorb water and become less effective in severe conditions.
C. Installation Considerations
Synthetic underlayment is lightweight and easy to install, making it less labor-intensive. Rubberized asphalt often comes with a self-adhesive backing, simplifying installation. Asphalt-saturated felt can be heavier and more challenging to work with, especially in cold or wet conditions.
D. Longevity and Maintenance Needs
Synthetic and rubberized asphalt offer longer lifespans and require less maintenance compared to asphalt-saturated felt, which tends to degrade faster and may need replacement sooner.
Who To Call For A Roof Leak
Selecting the right roof underlayment is vital for ensuring the longevity and effectiveness of your roofing system. With various options available, understanding their unique benefits can help you make an informed choice.
If you’ve noticed signs of a roof leak or suspect potential issues, it’s crucial to act quickly. For expert assistance, check out our blog on Who To Call For A Roof Leak to learn about the professionals who can help you address and resolve roofing concerns effectively.
