Types of Roof Underlayment

The roof plays a vital role in protecting your home from the elements. While shingles and tiles are the visible guardians, there’s an unsung hero hidden beneath – the roof underlayment. This essential component acts as a secondary barrier against moisture, providing an extra layer of defense for your home’s structure.

As roofing technology has advanced over the years, so too have the options for underlayment materials. So, how many types of roof underlayment are there?

In this article, we’ll explore the world of roof underlayment, shedding light on the materials that silently safeguard our homes from above. Each type offers unique benefits and characteristics, catering to different climates, roof designs, and budgetary considerations. Understanding these various options is key to ensuring your roof’s longevity, energy efficiency, and overall performance.

Join us as we uncover the unique benefits and limitations of each type, guiding your decision for the roofing project.

What Is Underlayment on a Roof?

Roof underlayment is an important protective layer installed directly on the roof deck, beneath the shingles or other roofing materials. It serves multiple important purposes, acting as a secondary defense against water infiltration, regulating roof temperature, and in some cases, providing fire resistance. This barrier covers the entire roof deck, creating a uniform surface for the roofing material and ensuring a smooth, even appearance of the finished roof. 

Underlayment also offers temporary weather protection during construction, allowing work to continue in less-than-ideal conditions. 

Modern underlayments have evolved from traditional felt paper to advanced synthetic materials, offering improved durability and protection. Building codes often require underlayment, recognizing its essential role in extending roof longevity and protecting the home’s interior from water damage.

Types of Roof Underlayment

Roof underlayment comes in various forms, each designed to provide specific benefits and protection for different roofing scenarios. From traditional felt paper to advanced synthetic materials, the choices available today cater to a wide range of needs and preferences. The right underlayment can significantly impact a roof’s durability, weather resistance, and overall performance. 

In this section, we’ll explore the most common types of roof underlayment, detailing their composition, advantages, and ideal applications so you can choose the right one for your needs. 

1. Asphalt-saturated felt

Asphalt-saturated felt is a traditional and widely used roofing underlayment. It’s made from natural fibers soaked in asphalt, creating a water-resistant barrier. Available in 15-pound and 30-pound varieties, it offers good protection at a relatively low cost. Felt allows the roof to breathe, helping to prevent moisture buildup in the attic. 

However, it can be prone to tearing during installation, especially in windy conditions, and UV exposure can lead to deterioration, limiting the installation window. While heavier than synthetic options, felt remains popular due to its long history of use and contractor familiarity.

2. Synthetic underlayment

Synthetic underlayment is made from polymers like polyethylene and polypropylene, providing superior strength and durability compared to felt. It’s lightweight, tear-resistant, and often UV-stable, allowing for longer exposure times during installation. Typically available in large rolls, it facilitates faster installation. 

Although more expensive than felt, synthetic underlayment’s durability and ease of use can justify the higher initial cost. Some synthetic materials may not allow moisture to escape, making proper attic ventilation crucial. The slippery surface can also pose safety concerns during installation, requiring extra precautions.

3. Rubberized asphalt underlayment

Rubberized asphalt underlayment combines rubber polymers with asphalt to create a flexible, waterproof material. Often featuring a sticky backing, it adheres directly to the roof deck, forming a watertight seal. 

This type is particularly effective in areas prone to ice dams and on low-slope roofs, as it seals around fasteners and provides excellent protection against water infiltration. Its flexibility allows it to conform to irregular surfaces, ensuring complete coverage. 

However, rubberized asphalt is more expensive than felt or basic synthetics, and its installation can be challenging due to the sticky backing. It also has limited breathability, potentially trapping moisture within the roof structure.

4. Non-bitumen synthetic underlayment

Non-bitumen synthetic underlayment is an environmentally friendly option made from polymers instead of asphalt. It’s lightweight, tear-resistant, and often features a slip-resistant surface, enhancing installation safety. 

Highly UV-resistant, this material can be left exposed for extended periods, offering flexibility in installation schedules. Many versions are also recyclable, making them appealing to eco-conscious homeowners. Although it is more expensive than felt underlayment, its durability and ease of installation can provide long-term benefits. 

However, some types of synthetic underlayment may not be as breathable as felt, so ensuring proper attic ventilation is crucial. Additionally, the material can be slippery when wet, which requires extra safety precautions during installation.

5. Self-adhered underlayment

Self-adhered underlayment features a sticky backing that bonds directly to the roof deck, creating a watertight seal. It is typically composed of a high-density polyethylene film top layer and a rubberized asphalt adhesive bottom, and it provides excellent waterproofing. 

Ideal for critical areas like eaves and valleys, or for entire roof coverage in harsh climates, this material effectively seals around fasteners to prevent water entry through nail holes. Installation is often quicker than other types because it generally doesn’t require separate fasteners. 

However, it’s one of the most expensive options, which can significantly impact project costs. Besides, installation requires careful attention, as mistakes are difficult to correct once the material is applied. Like rubberized asphalt, it doesn’t allow for moisture vapor transmission, making proper attic ventilation essential.

Conclusion

We hope this article has helped you understand the diverse landscape of roof underlayment types, enabling you to make a better decision for your roofing needs. Remember, the right choice depends on factors such as climate, roof design, and budget. 

The various types of roof underlayment offer unique advantages and considerations for different roofing projects. From the traditional asphalt-saturated felt to advanced synthetic and self-adhered options, each material plays an essential role in protecting your home from the elements. 

Whether you opt for the cost-effective felt or the high-performance rubberized asphalt, selecting the appropriate underlayment is a key step in ensuring your roof’s longevity and effectiveness. 

As roofing technology continues to evolve, staying informed about the latest developments in underlayment materials will help you make the best choices for your home’s protection.