Strong and durable roofing systems can help homes withstand inclement weather, provide improved energy efficiency, and allow a wider range of aesthetic potential. For metal roofing systems specifically, the panels’ substrate and finish offer several advantages to residential design. Taking things one step further, underlayment, an often-overlooked component of the complete roof system, can help a metal roof maximize its performance potential.
A high-quality underlayment is critical for both new construction and re-roofing projects alike. When it comes to re-roofing projects, it is possible that several advancements in underlayment technology have happened since the original roof was installed, given traditional roofing materials last between 15 and 30 years and metal roofs can last up to 70 years.
The following is a guide to picking the right underlayment for a project’s needs.
Underlayment is a protective layer installed between the roof deck and the surface roofing material (i.e. the metal roof panels). Ultimately, it contributes to the overall health of a roof system. In addition to providing a smoother surface for the metal panels to be installed on top of, underlayment maximizes the performance capabilities a metal roof offers by doing these things:
• Provides a secondary barrier against moisture and condensation• Self-seals around roofing nails, screws, and roofing clips to prevent water intrusion• Mitigates heat transfer from structural roofing elements for increased efficiency• Offers sound-deadening properties to dampen noise transfer from the outside
While metal roofs deliver long-term value on their own merit, underlayment still provides a must-have critical layer of protection. Contractors are encouraged to select a modern synthetic underlayment with self-sealing and high-temperature properties for a metal roof. This type of underlayment has a lifespan that is comparable to the long service life of metal roofing panels. With a self-healing underlayment, contractors have less risk of creating holes that allow moisture in. This is important for installation efforts and accommodating future roof upgrades.
Underlayment with high-temperature properties can withstand temperatures of up to 250°F without degradation, ensuring structures in even the hottest locations are protected. This type of underlayment is often UV-resistant to reduce damage from direct sunlight. Further, most high-temperature underlayment resists tearing and can stretch upwards of 250%. As such, tested products like MetShield® HT are essential for homes in Arizona, New Mexico, Texas, Southern California, and anywhere else that experiences high heat.
On the opposite end of the weather spectrum are northern climates, which often experience extreme freeze-thaw cycles that cause materials to expand and contract at different rates. In these conditions, underlayment with self-healing properties can help mitigate issues from deck expansion and contraction. They also create a secondary boundary to water intrusion from ice and snow melt.
It’s also important to note that installing underlayment according to the manufacturer’s instructions ensures that metal panels and underlayment work together without compromising weather protection. While installation can vary slightly between systems, it is typically recommended that contractors install an underlayment horizontally across the roof deck and work from the bottom to the top, overlapping strips of underlayment to ensure full effectiveness. For all areas of installation, contractors are encouraged to install underlayment using corrosion-resistant cap nails with a minimum 1-inch diameter cap, unless the product is self-adhered.
For more information on the benefits of underlayment and how to install a full metal roofing system to maximize its potential, reach out to your Drexel Metals Representative.
