Metal Roof Underlayment (Standards, Types, & More)

Choosing the right metal roof underlayment is one of the most important steps in building or renovating a roofing system for residential and commercial properties. This unseen layer serves as the last line of defense against water infiltration, extreme temperatures, and wind-driven rain. Whether you’re a homeowner looking to upgrade your roof or a property manager handling a commercial building, understanding underlayment options and standards will help protect your investment.

In this blog, you’ll learn:

• The purpose and importance of metal roof underlayment
• The types of underlayment available for metal roofing
• Key standards and installation tips for long-lasting performance

If you’re planning a roofing project, this guide will help you choose the best underlayment for long-term durability and protection.

🤔 What Is Metal Roof Underlayment?

A Protective Barrier Beneath the Metal

Metal roof underlayment is a water-resistant or waterproof layer installed directly over the roof deck and beneath the metal roofing panels. Its purpose is to provide additional protection from moisture, ice, and heat.

Why It’s Necessary

Metal roofs expand and contract with temperature changes. This movement can cause seams or fasteners to shift slightly over time. Underlayment helps protect against water leaks, especially in areas with heavy rain, snow, or high humidity.

Where It’s Used

• Residential homes with pitched roofs
• Commercial properties with low-slope or steep-slope metal roofing
• Pole barns, agricultural buildings, and industrial warehouses

Proper underlayment ensures the entire roof system performs at its best, regardless of the building type.

📋 Common Types of Metal Roof Underlayment

Different buildings and climates call for different types of underlayment. Each material has strengths depending on the structure’s needs.

Felt Underlayment

Also known as asphalt-saturated felt, this is one of the oldest and most commonly used underlayments for residential roofs.

• Made from organic or fiberglass base
• Typically available in 15-pound and 30-pound thickness
• Offers basic water resistance and UV protection

Felt is cost-effective but may not last as long or perform as well under extreme heat as modern options.

Synthetic Underlayment

Made from polypropylene or polyethylene, synthetic underlayment is increasingly popular in both residential and commercial applications.

• Lightweight and tear-resistant
• Water-repellent with a slip-resistant surface
• UV resistant and suitable for high-temperature environments

It’s more durable than felt and can be left exposed for longer during installation.

Peel-and-Stick (Self-Adhering) Underlayment

This rubberized asphalt or butyl-based product sticks directly to the roof deck for maximum waterproofing.

• Ideal for areas prone to ice dams and heavy rain
• Self-sealing around nails and fasteners
• Commonly used in valleys, eaves, and low-slope roofs

This option provides high performance in tough conditions but comes with a higher cost.

🔑 Key Standards for Metal Roof Underlayment

Before selecting an underlayment, it’s important to understand the standards and requirements that guide its use in residential and commercial construction.

Building Code Compliance

Underlayment materials should meet local and national building code standards. These often include:

• International Residential Code (IRC)
• International Building Code (IBC)
• ASTM standards (American Society for Testing and Materials)

Make sure the underlayment you choose meets these codes for wind uplift, fire resistance, and water infiltration.

Fire Rating

Especially in commercial settings or wildfire-prone regions, the underlayment should have a Class A fire rating when used with a metal roofing system.

Ice and Water Shield Requirements

Some local codes require self-adhering ice and water barriers in areas with frequent freeze-thaw cycles. These are typically installed along roof edges and valleys.

✅ Choosing the Right Underlayment for Your Property

Both homeowners and property managers need to consider several factors when choosing metal roof underlayment. Here are five key points to guide your decision.

1. Building Type and Usage

• Residential homes often use synthetic or felt underlayment
• Commercial buildings may require peel-and-stick for low-slope sections
• Agricultural structures may benefit from cost-effective felt with proper ventilation

2. Climate Conditions

• In wet or snowy climates, waterproofing is essential
• Hot, sunny regions require UV- and heat-resistant materials
• Freeze-thaw areas should use ice and water barriers near the edges

3. Roof Slope

• Steep-slope roofs can shed water easily, so synthetic underlayment may be sufficient
• Low-slope roofs are more vulnerable to standing water, requiring peel-and-stick options

4. Budget and Longevity

• Felt is more affordable but may wear out faster
• Synthetic and peel-and-stick options offer better long-term value
• Investing in quality underlayment saves money on future repairs

5. Installation Timeframe

• Synthetic underlayments are lighter and easier to install quickly
• Peel-and-stick requires precise application but provides maximum protection
• Choose the right balance between labor cost and performance

🛠️ Installation Tips for Metal Roof Underlayment

Even the best materials can fail without proper installation. Here are a few tips for getting it right.

Prepare the Roof Deck

• Ensure the deck is clean, dry, and free of debris
• Replace any damaged plywood or OSB
• Smooth out bumps or nails that could puncture the underlayment

Follow Manufacturer Guidelines

• Always use fasteners recommended by the underlayment manufacturer
• Avoid overdriving nails or staples
• Overlap seams according to instructions (commonly 4 inches or more)

Protect Vulnerable Areas

• Install additional peel-and-stick underlayment in valleys and around chimneys
• Apply ice and water barriers along eaves and gutters
• Seal overlaps and joints carefully to prevent water intrusion

⏰ Maintenance and Lifespan

Metal roof underlayment is hidden from view, but it plays a vital role over time.

How Long Does It Last?

• Felt: 10 to 15 years
• Synthetic: 25 to 40 years
• Peel-and-stick: 30 to 50 years or more

The lifespan depends on installation quality, exposure to weather, and the roofing system above it.

Periodic Inspections

• Check for water stains in attics and ceilings that could signal underlayment failure
• Inspect the roof annually or after major storms
• Ensure flashing and sealants are intact to support the underlayment

⭐️ Advantages of Quality Underlayment in Residential and Commercial Projects

High-quality underlayment provides benefits that go beyond basic waterproofing.

• Energy Efficiency: Some synthetic underlayments offer radiant barriers or reflectivity to improve temperature control in buildings.
• Noise Reduction: Underlayment helps buffer sound, reducing the noise from rain or hail hitting the metal panels.
• Improved Durability: Protecting the decking from moisture prevents rot and mold, which strengthens the roof’s structure over time.

Trust Embry’s Roofing for Expert Metal Roof Systems

Metal roof underlayment is a critical component for protecting your home or commercial building from moisture and structural damage. Whether you’re building a new property or replacing an old roof, the right underlayment ensures long-term performance and peace of mind.

At Embry’s Roofing, we work with both residential homeowners and commercial property managers to select and install high-quality roofing systems from the deck up. Our team understands the unique needs of every building and delivers reliable, code-compliant underlayment solutions for any project.

Ready to upgrade your roof with professional underlayment installation? Contact Embry’s Roofing today and get lasting protection for your property.