Why roofing underlayment is the quiet hero of weatherproof construction

By Jesse Sanchez. 

The first line of defense against leaks and mold might be something you never see — but absolutely need in place. 

When it comes to preventing costly roof failures, the underlayment isn’t just an accessory — it’s the unsung champion of every well-built roofing system. 

From brutal snowstorms to punishing summer heat, the roof takes the full brunt of nature. And while shingles do the visible work, it’s what lies beneath that often determines the system’s longevity. That’s where roofing underlayment steps in. Acting as a secondary moisture barrier, high-quality underlayment like CertainTeed’s RoofRunner® and Grace Vycor™ Ice & Water Shield® plays a critical role in reducing callbacks due to leaks. 

Underlayment is your last line of defense when shingles are compromised. Products such as WinterGuard® are engineered to self-seal around nails and resist wind uplift — ideal in areas prone to ice dams or wind-driven rain. The brand’s DiamondDeck® option adds puncture resistance and water-resistance in a lightweight synthetic layer, suitable under virtually any roof material. 

But underlayment does more than just block water. Certain systems, like CertainTeed’s Integrity Roof System®, are designed to promote attic airflow, which helps combat mold, prevent condensation and keep interior temperatures in check. A properly ventilated and sealed roofing system not only extends the life of materials but protects the health of the home itself. 

The full CertainTeed system also offers another layer of protection: comprehensive warranty coverage. Homeowners who install a complete CertainTeed roof with all components — from starter shingles to ridge vents — may be eligible for extended warranties that cover both materials and labor. In other words, investing in a full system pays dividends in peace of mind. 

While homeowners may be tempted to skip over what they can’t see, professionals know that cutting corners on underlayment can mean big problems down the road. As CertainTeed notes, “Unpredictable weather is no match for a well-protected roof.” 

For anyone involved in roofing — builder, contractor or homeowner — it’s worth a deeper look at what underlayment does and how CertainTeed's complete system approach stands out. The right materials under the shingles might be the best decision you never see. 

Learn more about which underlayment is right for your region or roofing material!