If you’re installing an asphalt shingle roof, you might be asking: Is underlayment really necessary? It’s a common question among both contractors and homeowners. While the answer might seem straightforward, there are important technical and regulatory factors to consider—making the reality more nuanced than it first appears. Here’s what you need to know:
Is Underlayment Required?
Short answer: In most cases, yes.
Across the U.S., most local building codes require the use of underlayment beneath asphalt shingles. While there may be exceptions in certain regions without formal code enforcement, skipping underlayment introduces serious risks—including leaks, water damage, and voided manufacturer warranties.
Even when not explicitly required, underlayment is widely considered a best practice. It provides an added layer of protection against weather-related damage and helps ensure the long-term performance of the roof. If you’re unsure about local code requirements, it’s always best to check with your local building authority or inspector.
Skipping Underlayment May Void Shingle Warranties
Even if local codes are lenient, skipping underlayment can come back to haunt you financially. Most asphalt shingle manufacturers offer warranties that are only valid if the roofing system, including the underlayment, is installed according to their specifications.
Failing to install a qualifying underlayment can lead to a rejected warranty claim, especially if leaks, mold, or water damage occur. Reputable manufacturers require synthetic or felt underlayment as part of their system warranties. Always check manufacturer guidelines before installation to ensure warranty compliance.
Why Professionals Always Use Underlayment
Regardless of whether it’s explicitly required, using underlayment beneath asphalt shingles is best practice—and for good reason.
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Moisture Defense
Shingles may shed most of the water from a roof, but they aren’t a complete barrier—especially during wind-driven rain, melting snow, or ice dams. Moisture can still work its way beneath the shingle layer and, without underlayment, soak directly into the roof deck. That’s where serious problems start: rot, mold growth, and costly structural damage.
High-quality synthetic roofing underlayment provides a secondary moisture barrier that protects the roof deck when shingles are compromised. Unlike felt, which can wrinkle, absorb water, or deteriorate over time, synthetic materials are water-repellent, non-absorbent, and built to perform. Epilay’s synthetic underlayment is engineered to deliver this reliable backup layer, keeping moisture out and your roofing system intact.
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Temporary Protection Before Shingle Installation
Roofing projects don’t always go according to schedule. Delays from weather or crew availability can leave exposed underlayment on a roof deck for days or even weeks. High-quality synthetic roofing underlayment is UV-resistant for extended periods (up to 180 days in Epilay’s case), offering protection until the shingles are installed.
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Added Safety and Durability
Products like Epilay’s synthetic roofing underlayment are engineered to improve jobsite safety with superior slip resistance and tear strength. Compared to traditional felt, synthetic options are lighter, faster to install, and more durable under foot traffic—all major advantages for contractors and installers.
Comparing Felt vs. Synthetic Underlayment
Traditional felt underlayment has been around for decades, but it comes with limitations. It absorbs moisture, making it prone to wrinkling, tearing, and rot. Felt is also heavier, harder to handle, and offers minimal traction—especially in wet or cold conditions. Exposure to sunlight quickly degrades its integrity, limiting installation flexibility.
On the other hand, synthetic roofing underlayment—like those from Epilay—offers a clear upgrade. Made from water-repellent, non-absorbent materials, synthetics resist mold and maintain their structure even in extreme conditions. They’re lightweight, easy to install, and far more tear-resistant, holding up to foot traffic and fasteners with ease. Features like GripWalk™ and Skid-Resist® provide much-needed traction for safer, faster installations. Plus, with UV protection for up to 180 days, you get more flexibility on the jobsite.
For contractors prioritising efficiency, safety, and long-term performance, synthetic underlayment isn’t just an option—it’s the standard.
Underlayment Is Not Optional—It’s Essential
Even when building codes don’t spell it out, synthetic roofing underlayment is still a smart investment. It safeguards the roof deck, supports long-term shingle performance, and provides an extra layer of security against leaks, weather, and warranty issues. No professional roofer would recommend skipping it.
Ready to Make the Smart Choice?
Protect your project from unnecessary risks. Choose an underlayment that meets code requirements, supports manufacturer warranties, and holds up in real-world conditions. Epilay’s synthetic roofing underlayment is engineered for performance, durability, and ease of use—everything a roofing system needs to last. Contact us today or visit epilay.com to learn more and find a rep near you.
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