Deciding between felt and synthetic roof underlayment

By Jesse Sanchez. 

Choosing the right underlayment is a pivotal step in ensuring your roof stands strong against the elements while maximizing efficiency and durability. 

When it comes to building or replacing a roof, homeowners often focus on visible elements like shingles or tiles. However, a critical component lies beneath — roofing underlayment. This layer, situated between the outer roofing material and the sheathing, plays a pivotal role in safeguarding your home against moisture, extreme temperatures and even structural damage. Choosing between traditional felt and modern synthetic underlayment involves weighing the pros and cons of both materials. 

The role of underlayment 

Roof underlayment acts as a protective shield, working behind the scenes to keep your roof functional. It prevents moisture intrusion, which can lead to mold, rot and costly repairs. Additionally, it provides an extra layer of insulation, reducing heat transfer into your home during summer and keeping energy bills in check. A lesser-known benefit? Underlayment can even serve as a noise barrier during rainstorms. 

Despite its hidden nature, underlayment is essential for a roof’s longevity and is often required to maintain manufacturer warranties for shingles or tiles. With its importance established, the next decision becomes which material to use: traditional felt or synthetic underlayment. 

Traditional felt: A time-tested solution 

Felt underlayment, constructed from asphalt-saturated organic or fiberglass materials, has been a staple for decades. Its primary allure lies in its affordability and simplicity. Available in different thicknesses, it provides adequate protection for many roofing needs, particularly for budget-conscious homeowners. 

Yet, felt comes with drawbacks. It is heavier than synthetic options, can wrinkle or tear during installation, and is less resistant to prolonged moisture exposure. Furthermore, its weight and handling complexity can lead to higher labor costs. For those working on steep or complex roof pitches, felt’s slippery surface can pose safety risks. 

Synthetic underlayment: The modern contender 

Synthetic underlayment, made from advanced polymers like polyethylene or polypropylene, offers a host of benefits. It is lightweight, durable and resistant to UV rays, making it easier to handle and install. Its thin composition minimizes the added weight on a roof, a crucial advantage for older homes with less robust structures. Synthetic underlayment is also far more resistant to tearing and moisture damage, providing superior protection in extreme weather. 

However, synthetic underlayment is not without its challenges. It is generally more expensive and some regions still mandate the use of felt underlayment due to building code restrictions. Additionally, synthetic materials act as vapor barriers, which can exacerbate ventilation issues if not properly addressed. 

Making the right choice 

Choosing between felt and synthetic underlayment requires careful consideration of your roof’s specific needs, local regulations and budget. Some manufacturers stipulate the use of synthetic underlayment to preserve warranty coverage for their shingles or tiles, while others may accommodate either material. Similarly, certain roofing contractors might specialize in one type over the other based on safety and efficiency during installation. 

Ultimately, your decision should balance immediate cost with long-term performance. While felt is economical and widely accepted, synthetic underlayment may provide better protection and durability, especially in areas prone to harsh weather conditions. 

Learn more about the differences between felt and synthetic underlayment and discover which option is best suited for your roofing needs by consulting experienced professionals today!