Choosing the Right Underlayment for a Metal Roof

Roofing underlayment is a critical component of any new roofing project or re-roofing undertaking. Underlayment materials offer a water-shedding barrier against moisture infiltration, adding another protective layer to your roof. They're typically installed on top of your roof deck, which is usually made of either OSB or plywood. Roofing cladding are then placed on top of the underlayment.

Metal roofs have unique characteristics, which should factor into your decision when choosing an underlayment product. Read on to discover the best metal roofing underlayment for your home.

Metal Roofing Underlayment Considerations

Roofing underlayments are essential for metal roofs as with other roofing claddings, such as asphalt, tile, or slate. As a secondary protective layer, they help repel water from heavy rains, melting snow and, in colder regions, ice dams.

Metal roofs generate a lot of heat beneath their surface, so underlayments placed under metal roofs must meet standards for high temperature use. You should also review the roofing manufacturer’s guidelines for proper installation and compatibility.

Before deciding on an underlayment for your metal roofing project, answer the following questions:

• Does the material provide a sufficient barrier to moisture?
• Where is your home located — regionally and climate-wise?
• What are the local building regulations?
• What products do the roofing contractors in your area use?
• What is the slope of your roof?

Roofing Underlayment Materials

Underlayments for metal roofs are categorized based on application and installation methods.

• Self-Adhered (also called Ice and Water Barrier)
• Synthetic

Why Not Felt?

Synthetic roof underlayments outperform felt across the board, regardless of your roofing material, i.e., asphalt, tile, or metal. Felt underlayments have been around for a long time, but synthetic underlayments' durability and performance make them top contenders for today's roofing projects.

Disadvantages of felt include its tendency to:

• Easily tear
• Absorb water
• Weigh more than synthetics
• Wrinkle
• Provide less traction than synthetics

Self-Adhered Underlayments

Self-adhered roofing underlayments are a great choice for homeowners who want advanced protection underneath their metal roofs. The sticky backing adheres tightly to the roof deck, creating a waterproof seal and ice dam protection, especially in eaves, valleys, and dormers (dormers are windows that extend out of your roof slope). Self-adhered waterproof underlayments can be used over the entire roof deck or just in vulnerable areas of your roof.

The combination of flexible installation, non-skid surfaces, and extreme adhesion make self-adhered underlayments an appealing solution to homeowners and roofing contractors alike.

Owens Corning offers a selection of self-adhered underlayments suitable for installation under a metal roof.  By creating a secondary barrier against moisture intrusion, these products help support the integrity of your metal roofing system.

• WeatherLock® Specialty Tile & Metal
• Titanium® PSU30
• Titanium® FR

Synthetic Underlayments

Synthetic roof underlayments are comprised of durable synthetic fibers woven together to form a strong surface with a high tear strength. No tears mean no openings for moisture to infiltrate. The outer covering is water-repellant as well, so any water that reaches the underlayment won't hang around, lessening your risk of mold.

Synthetic roofing underlayments usually have a non-skid coating, which helps enhance worker safety and speed installation. In addition, manufacturers typically print delineations and markings for fasteners on the exterior surface, helping to ensure consistent and accurate placement.

Synthetic underlayments are an excellent choice for metal roofing installations. If installed according to manufacturer recommendations, they're more durable than felt products and simpler to install.

• Significantly stronger than felt underlayment, resisting tears and standing up to foot traffic
• Can withstand extended UV exposure during installation without a decline in durability, in some instances up to 180 days
• Considerably lighter than No. 30 felt
• Wider and longer in roll size than felt paper, reducing ladder trips

Owens Corning offers homeowners a choice of synthetic underlayments for their metal roofing system. Each product provides advanced protection for your roof deck and contains unique features to meet your specific needs.

• ProArmor®
• DeckDefense®
• RhinoRoof® U20
• Titanium® UDL25, UDL30, and UDL50
• Titanium® X30

Owens Corning Underlayment Products for Metal Roofs

You want your metal roof system to last for many years. That's why it makes sense to protect your roof deck from eave to peak. Find out more about Owens Corning underlayment products for metal roofing projects and discover what makes each option unique.

Self-Adhered Underlayments (Ice and Water Barrier Products)

Owens Corning WeatherLock® Specialty Tile & Metal

The self-sealing action of this self-adhered barrier helps prevent water intrusion around fastenings and any other roof penetrations. In addition, the single-layer polyester fabric can withstand the high surface temperatures that metal roofing systems can generate.

• UV rays resistance: 180 days
• Traction: slip-resistant non-woven polyester
• High temperature rated for metal roofing system
• Warranty: 30-year Limited^†

Titanium® PSU30

This flexible water barrier gives your roof deck a layer of defense, whether threatened by ice dams in the winter or high temperatures in the summer. The underlayment is composed of modified rubberized asphalt with a synthetic facer, creating a durable barrier that lies flat and secure under metal undersurfaces. Titanium® PSU30’s extreme walkability and superior deck adhesion make it a smart choice for steep-sloped metal roofs.

• UV rays resistance: 180 days
• Traction: Sure-Foot® nodular walking surface
• High temperature rated for metal roofing system
• Warranty: Limited Lifetime^†

Titanium® FR

Homes in Wildland Urban Interface (WUI) zones have strict building codes regarding fire resistance. Titanium® FR underlayment can help your metal roofing system achieve the necessary Class A Fire Rating thanks to its proprietary technology that helps minimize fire spread to the roof decking.

• UV rays resistance: 180 days
• Traction: Sure-Foot® nodular walking surface
• High temperature rated for metal roofing system
• Warranty: Limited Lifetime^†

Synthetic Underlayments

Owens Corning ProArmor®

Synthetic underlayments offer enhanced moisture protection under metal roofs, performing better overall than felt. ProArmor® is up to 12 times stronger than felt^‡‡  and each roll provides up to 450% more coverage than competitive felt underlayments.^‡ Less trips up the ladder and a slip-resistant surface helps promote a trouble-free installation.

• UV rays resistance: 90 days
• Traction: Fusion Back Coating Technology®
• High temperature rated for metal roofing system
• Warranty: 10-year Limited^†

Owens Corning Deck Defense®

This synthetic underlayment features a textured outer surface for ease of installation regardless of the weather or steepness of the roof deck. Strong and durable, it’s an ideal complement to your metal roofing system.

• UV rays resistance: 180 days
• Traction: TruTread™ textured surface
• High temperature rated for metal roofing system
• Warranty: Limited Lifetime^†

Titanium® UDL25, UDL30, and UDL50

The Titanium® family of synthetic underlayments offers homeowners a much-needed alternative to felt for residential roofing systems. All three are compatible with metal roofs and have a significantly stronger tear strength than felt. The product’s roll size and lighter weight (compared to felt) ease installation time and labor.

• UV rays resistance: 180 days
• Traction: Sure-Foot® nodular walking surface
• High temperature rated for metal roofing system
• Warranty: Lifetime limited
• Tear strength compared to No. 30 felt:

                  UDL25: 14x

                  UDL30: 20x

                  UDL50: 25x

Titanium® X30

For secure footing, regardless of conditions or roof slope, consider Titanium® X30 with Comfort Grip™ Technology. The premium underlayment offers the same advantages and performance as the Titanium products listed above, along with superior cushion and traction for extreme walkability.

RhinoRoof® U20

Enhanced durability and wind resistance are hallmarks of the RhinoRoof® brand. This synthetic underlayment holds up to heavy foot traffic, resisting sliding and tearing and providing an excellent gripping surface.

• UV rays resistance: 90 days
• Traction: FiberGrip surface
• High temperature rated for metal roofing system
• Warranty: 20-year limited

Which Type of Metal Roofing Underlayment Is Best for You?

The type of metal roofing underlayment that's best for your home depends on the specifics of your project, budget, and building code regulations. Manufacturers often specify whether their materials are appropriate for particular types of metal roofing, regional requirements, and roof slopes.

Testing Standard for Synthetic Underlayment

Recent efforts by a task group (members include manufacturers like Owens Corning, roofing contractors and consultants) have helped initiate a testing standard for synthetic underlayments. ASTM D8257 from the American Society for Testing and Materials lists requirements for synthetic underlayments. This standard makes it easier to compare synthetic underlayment products accurately.

Ask Your Independent Roofing Contractor

An experienced roofing contractor can help answer questions you might have about what material to use for your roofing underlayment. That's why it's so important to choose a knowledgeable roofing professional. The Owens Corning Roofing Contractor Network is made up of independent roofing contractors who've demonstrated their reliability and craftsmanship. You can search by zip code to find one in your area.

FREQUENTLY ASKED QUESTIONS ABOUT METAL ROOF UNDERLAYMENTS

Underlayment products help increase your metal roof's longevity by offering a secondary level of protection. To learn more about this critical roof component, browse this list of FAQs.

Q. Is roof underlayment necessary?

A. Yes. Underlayment is your roof deck's last line of defense should moisture make it past your shingles. While shingles help your roof shed water, synthetic underlayments repel water that may creep underneath shingles — possibly from ice dams or wind-driven rain. Owens Corning refers to this protection as "SEAL." within the Total Protection Roofing System®. 

Learn More about the Total Protection Roofing System®

Q. What are the different types of roofing underlayment for metal roofs?

A. Synthetic underlayments and self-adhered ice and water barriers are the favored underlayment choices for a metal roof. Both can handle the high temperatures that may occur with metal roofs.

Q. How do I choose a roof underlayment?

A. Ask your roofing contractor which roof underlayments they recommend for your metal roofing project. Then, compare the options to see which is best for your locale and budget.

Q. Is synthetic roof underlayment waterproof?

A. A quality self-adhered roof underlayment, such as Owens Corning Titanium® PSU30, is designed for waterproofing protection. Once installed, it creates a waterproof barrier against water infiltration.

Other synthetic underlayments — those that are not self-adhering — offer a water-shedding barrier as opposed to a waterproof barrier. Both types of products are non-absorbent, resistant to tears, and help reduce moisture intrusion.