by Kes Anderson
While shingles create the visible surface of your roof, the real performance depends on the roof underlayment, the hidden layer that safeguards your home from moisture and damage. When most people picture a roof, they think of shingles, the visible layer that defines a home’s look and shields it from the elements. But what really determines how well your roof performs lies beneath the surface. That hidden but essential layer is called the roof underlayment, and it plays a critical role in keeping your home dry, insulated, and protected year after year.
Installed directly over the roof deck and underneath the shingles, the underlayment acts as a moisture barrier and temperature buffer, preventing leaks and structural damage while supporting the overall roofing system. In this guide, our experts explain the different types of roof underlayment, how they work, and which one provides the best protection for your home.
Why Roof Underlayment Matters
Your roof’s primary job is to keep water out, but shingles alone cannot always do it. Strong winds, heavy rain, or melting snow can push moisture beneath the surface. The roof underlayment serves as your roof’s secondary line of defense, sealing the deck against water intrusion that could otherwise lead to rot, mold, or insulation damage. According to the National Roofing Contractors Association, underlayment is a crucial part of a roofing system that provides an extra layer of protection between the shingles and the home. A high-quality roof underlayment ensures that even when shingles are compromised, your home stays protected from leaks and moisture damage.
It also helps smooth out the roof deck for shingle installation and provides an added layer of insulation, reducing heat transfer and helping your home stay more comfortable. By acting as a backup barrier when shingles lift, crack, or age, underlayment can prevent costly leaks before they ever reach your attic.
The Three Main Types of Roof Underlayment
There are three primary materials used in modern roofing: asphalt-saturated felt, rubberized asphalt, and synthetic underlayment. Each has unique strengths, costs, and applications depending on your home’s design and your local climate. The U.S. Department of Energy also highlights the importance of proper underlayment and roof insulation for energy efficiency and home protection.
Asphalt-Saturated Felt
Often referred to as felt paper or tar paper, asphalt-saturated felt has been a roofing staple for decades. Made from either cellulose or fiberglass mat soaked in asphalt, it provides a basic level of water resistance and a modest layer of protection between the roof deck and shingles.
Homeowners often choose felt underlayment for smaller or lower-cost projects such as detached garages or sheds. It is affordable, easy to find, and can deliver adequate short-term performance. Heavier versions, like 30-pound felt, offer better durability than the thinner 15-pound type, making them more suitable for full residential roofs.
However, felt’s simplicity comes with trade-offs. It is not waterproof, only water resistant, and it can absorb moisture, leading to wrinkling or tearing if left exposed too long. In extreme heat, it can dry out and crack; in very cold conditions, it may become brittle. While felt remains a budget-friendly solution, it lacks the longevity and flexibility of more advanced materials. For a roofing upgrade that balances cost and durability, choosing a modern roof underlayment can make a significant difference in long-term performance.
Rubberized Asphalt
Rubberized asphalt represents the premium end of roof underlayment, offering the highest level of waterproofing available. This material combines asphalt with rubber polymers, creating a flexible, self-adhering membrane that bonds directly to the roof deck. The result is a watertight seal that can withstand harsh climates and resist cracking even when temperatures fluctuate dramatically.
This type of roof underlayment is especially effective in leak-prone areas such as valleys, chimneys, skylights, vents, and eaves—anywhere water naturally collects or flows. Because it is self-sealing and self-healing, rubberized asphalt can close around nail holes or minor punctures, preventing moisture from finding its way through. It performs exceptionally well in heavy rain, snow, and ice, making it an ideal option for homes in the Pacific Northwest and other regions that experience long, wet winters.
Of course, that level of performance comes at a higher cost. Rubberized asphalt is more expensive than other options and requires skilled installation to ensure the adhesive backing is properly applied. For many homeowners, it is best used as a targeted barrier in vulnerable roof sections or as part of a premium, full-system replacement where long-term waterproofing is the top priority.
Synthetic Underlayment
Synthetic underlayment has become the new standard for residential roofing, and for good reason. Manufactured from polypropylene or polyethylene, it is stronger, lighter, and more resistant to tearing than traditional felt. Its woven or spun design gives it excellent durability, while its water-resistant surface helps block moisture without trapping it inside.
Unlike asphalt felt, synthetic materials do not absorb water or wrinkle when wet. That means they maintain their shape and continue to protect the deck even in changing weather conditions. Roofers also prefer synthetic underlayment because it is lighter and easier to handle, and many versions include anti-slip surfaces that make installation safer and faster.
Another advantage is heat tolerance. Synthetic underlayment can withstand higher temperatures, making it particularly suitable for metal roofs or homes exposed to direct sunlight. While the upfront cost is slightly higher than felt, the longer lifespan and lower maintenance make it a more economical choice in the long run. It offers a perfect middle ground, more affordable than rubberized asphalt but far more resilient than traditional felt.
Integrity Roofing’s Choice: Synthetic Breathable Underlayment
At Integrity Roofing and Construction, we have worked with every type of roofing system and underlayment available, and our professional recommendation is clear. Synthetic breathable roof underlayment delivers the best performance for most homes.
We use advanced, breathable products from trusted manufacturers, designed to provide superior leak protection and long-term durability. These materials allow trapped moisture to escape from beneath the roof while keeping water from penetrating the surface, an ideal balance for maintaining a dry, healthy roofing system.
Synthetic underlayment also enhances safety during installation with its slip-resistant texture and stable structure. It does not degrade under UV exposure if the project takes more than a day or two to complete, and it stays flexible through heat and cold alike. Because it is recyclable and long-lasting, it is also one of the most environmentally responsible choices available today.
When installed by our certified roofing specialists, this type of underlayment creates a dependable shield between your shingles and roof deck, extending the life of your roof and protecting your home through every season.
The Power of Professional Installation
Even the most advanced roof underlayment can fail if it is installed incorrectly. Overlaps, fastener placement, and sealing details all affect how well the barrier performs. At Integrity Roofing and Construction, our installation teams are trained to meet and exceed manufacturer specifications for every product we use. From the deck to the ridge vent, each layer is applied with precision to ensure your roof is watertight, ventilated, and built to last.
That professional attention to detail is what allows us to stand behind our work with confidence and why our customers trust us to protect what matters most.
Protect Your Home from the Inside Out
Your roof is more than shingles. It is a complete system designed to safeguard your home from rain, wind, and time itself. Choosing the right roof underlayment and having it installed by experienced professionals can make all the difference in how well your roof performs. Investing in premium roof underlayment today means fewer repairs, better insulation, and lasting protection for years to come.
If you are planning a roof replacement or simply want to learn more about your options, the team at Integrity Roofing and Construction is here to help. Call us at (360) 900-ROOF or schedule your free estimate online to get started. We will walk you through your choices, explain the benefits of each material, and help you choose a roofing system that is built for decades of reliable protection.
