Underlayment is the Key to Better Metal Roofing Systems

by Christopher Brinckerhoff | 2 May 2025 6:00 am

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Metal roofs come with several practical advantages, including a service life up to three times longer than asphalt shingle roofs. Incredibly versatile, metal roofs can also be customized to help architects and designers create statement-making roof designs. Metal roofs’ ability to deliver form and function is why metal roofing systems have become increasingly popular in residential and commercial applications over the last decade. While metal roofing panels deliver serious value, there is one key component of a roofing system that often gets overlooked: the underlayment.

A roof underlayment is a protective layer installed between the roof deck and the metal roofing panels. Ideal for new construction or retrofits, the underlayment can provide a smoother surface for the metal roofing panels to be installed on. This ensures the finished roof delivers a clean and aesthetically beautiful appearance. More important than style points, however, is this protective layer’s ability to contribute to the overall durability, weather resistance, and long-term performance of a roof. As a critical component of any roof system, the underlayment is important, and contractors need to recognize its benefits and know how to install it.

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Keeping moisture out

One of the key benefits of the underlayment is its ability to provide a secondary barrier against both water intrusion and condensation. While metal roofing panels offer premium weather resilience on their own merit, underlayments provide self-seals around roofing nails, screws, and roofing clips to prevent water intrusion in even the smallest points of penetration. This level of protection is especially critical during freeze-thaw cycles when materials expand and contract at different rates.

Additionally, the underlayment provides a vapor barrier to prevent moisture buildup. This helps protect the metal roofing panels themselves and safeguards the structural members of a roofing system.

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Reducing transfer of heat and noise

The right underlayment can also help increase a project’s energy efficiency by mitigating heat transfer from structural roofing elements to a building’s exterior. When combined with metal roof panels that are finished in a certified cool roof color, the underlayment can help reduce the energy required to maintain a consistent and comfortable temperature within a building.

An underlayment is critical in high-temperature applications, whether a roof is certified to cool standards or not. Consistently high temperatures and more-than-average sunlight can cause some underlayments and their adhesives to degrade over time—posing an unseeable risk to home and building owners. High-temperature underlayments can withstand temperatures of up to 121 C (250 F) without degradation, ensuring buildings in even the hottest locations are protected.

Finally, when an underlayment has sound-deadening properties, it can work with insulation to dampen noise from rain and hail—debunking the myth that metal roofing systems are noisy during a storm. In fact, metal roofs, with proper underlayment and insulation, are no louder than their asphalt or stone counterparts.

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Installation considerations

To capitalize on all the benefits that an underlayment provides, it is important to install it according to the manufacturer’s instructions. While installation can vary slightly between systems, it is often recommended for contractors to install an underlayment horizontally across
the roof deck, working from the bottom to the top, to align with the natural flow of water. In addition, it is important to overlap strips of underlayment to ensure full effectiveness.

In addition to the direction and starting location, many underlayment manufacturers recommend wrapping fascia boards along the rake edge and eaves for added protection from the elements. This also reduces thermal bridging between rafters
and paneling.

When contractors choose the right underlayment for a project and install it correctly, it can help metal roofing systems provide aesthetically pleasing protection for decades. An underlayment can also help roofing systems qualify for warranties, which benefits both the contractor and the home and building owner.

Brian McLaughlin is a graduate of Temple University and has been involved in the metal roofing industry for more than 15 years. In his current role, McLaughlin serves as the director of sales for Drexel Metals, a Carlisle company.  He has held many positions within Drexel Metals and has grown within the company and the industry as a leading expert in metal. For more information, visit drexmet.com/contact-us/[5].

Source URL: https://www.metalconstructionnews.com/articles/features/metal-roof-underlayment-drexel/

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