What’s the Best Underlayment for Metal Roofs?

Choosing the right underlayment is critical to your metal roof’s long-term performance. It’s not just a code requirement—it protects against moisture, adds insulation value, and can even prevent premature roof failure.

Here’s a breakdown of the best options and what homeowners in Colorado and Georgia need to consider.

Why Underlayment Matters Under a Metal Roof

Underlayment is the moisture barrier installed between your roof deck and metal panels. It helps:

• Prevent water intrusion from wind-driven rain or snow

• Protect the decking from condensation

• Improve fire resistance and insulation

• Meet local building codes

In metal roofing systems, underlayment also helps manage thermal movement and noise.

Best Types of Underlayment for Metal Roofs

1. Synthetic Underlayment (Most Common Today)

• Lightweight, durable, and easy to install

• Resistant to tearing and UV exposure

• Works well with standing seam and metal shingle systems

• Preferred by most installers in both Colorado and Georgia

Ideal for: All climates, especially where high winds and hail are common

2. High-Temp Ice and Water Shield

• Required in cold regions like Colorado where snow and ice damming are concerns

• Self-adhering and rubberized for waterproofing valleys, eaves, and penetrations

• Rated to withstand metal panel heat expansion without failure

Ideal for: Cold-weather zones, roof edges, valleys, and around skylights or chimneys
Code Note: Ice barrier underlayment is required along eaves in areas prone to ice dams per the IRC.

3. Rosin Paper (Slip Sheet)

• Used with high-temp ice and water shield in standing seam installations

• Allows panels to expand/contract freely without tearing the underlayment

Ideal for: Under metal panels installed with clips or exposed fasteners

What About Felt?

Traditional asphalt-saturated felt (like 30# felt) is still used in some cases but:

• It tears easily

• Isn’t suitable for long-term UV exposure

• May trap moisture under metal panels

Most contractors are shifting away from felt for metal roofing projects.

Regional Considerations

Colorado (Denver, Fort Collins, Colorado Springs)

• Use high-temp ice and water shield at eaves and valleys

• Synthetic underlayment for remaining roof area

• Consider a vented underlayment or cold roof system in mountain regions to manage snow load and freeze-thaw cycles

Georgia (Atlanta, Macon, Savannah)

• Use synthetic underlayment throughout

• Avoid felt—hot, humid conditions break it down quickly

• Ventilation is key to managing attic heat and moisture buildup

FAQs

What’s the best underlayment for metal roofs in snow country?

Use a high-temp ice and water shield at the eaves and valleys, plus synthetic underlayment on the remaining areas.

Can I put metal roofing directly on plywood?

No. Always use underlayment between plywood decking and metal panels to prevent moisture damage and meet code.

Does underlayment go under the entire metal roof?

Yes. Full-coverage underlayment is required under all metal roofs, with special materials used in vulnerable areas like valleys and edges.

Final Thoughts

If you're installing a metal roof in Colorado or Georgia, underlayment choice matters. Use a synthetic base with high-temp ice shield where needed, and make sure it meets local code and your roof’s slope and design.

For expert metal roofing installation or a quote, call Roof Nuts at:

Colorado: 303-276-2403
Georgia: 404-476-6851
Or visit RoofNutsCO.com or RoofNutsGA.com

Want help choosing the right underlayment for your roof slope and location? Let us know and we’ll help you plan it right.