Choosing the Right Underlayment for a Metal Roof

Roofing Contractors in Napa, CA, Explain the Differences Between Roof Underlayments

Making the Most of Your New Metal Roof

When it comes to metal roofing, the panels you see on top aren’t the only part that matters. Underneath that sleek, durable metal is a critical component that plays a huge role in your roof’s performance: the underlayment. Choosing the right underlayment for a metal roof can mean all the difference between a long-lasting solution for your home and a series of issues, including leaks and rising energy costs.

Whether you’re a homeowner or property manager, understanding your options can help you make the best decision for your project. In this blog, roofing experts delve into what underlayment is, the primary types to consider, and why collaborating with an experienced roofing company is crucial.

Why Is Metal Roofing Becoming So Popular?

Metal roofs have become a popular choice for residential and commercial roofing projects, particularly in areas such as California, where extreme weather conditions are a significant concern.

Here’s why:

• Longevity: Metal roofs can last 40–70 years, far outlasting traditional asphalt shingles.
• Durability: They’re resistant to high winds, hail, and even fire, making them an excellent investment in regions prone to storms or wildfires.
• Energy Efficiency: Many metal roofing systems reflect solar heat, which can lower your cooling costs significantly in sunny climates.
• Low Maintenance: Unlike some other materials, metal doesn’t warp, crack, or require constant roofing repair.
• Aesthetic Appeal: Modern metal roofs come in a variety of colors, profiles, and finishes, adding a sleek, contemporary look to any property.

What is Roof Underlayment?

Now that we understand why the material is gaining popularity in the area, what is the best way to ensure a new roof installation project lasts as long as possible? It all comes down to the materials under the new roof. Roof underlayment is a protective layer that’s installed directly on top of your roof deck and underneath your final roofing material. Think of it as your roof’s hidden superhero. Although it may not be visible once the metal panels are in place, it plays a crucial role in keeping your property safe and dry.

Why Underlayment Matters for Metal Roofs

Underlayment provides an essential second line of defense against water, wind, and other elements. If water sneaks under the metal panels, whether from driving rain, ice dams, or condensation, underlayment prevents that moisture from reaching your wood decking or attic insulation.

But it’s not just about leaks. Underlayment also helps regulate temperature and moisture beneath the metal panels. By creating a protective barrier, it shields your roof’s structure from rot, mold, and other damage that can develop when water and heat get trapped below the surface. The right underlayment helps:

• Prevent leaks and water damage: Especially important in areas prone to heavy rain or snow.
• Protect against condensation: Metal can “sweat” in the right conditions, and underlayment prevents that moisture from reaching your roof deck.
• Enhance energy efficiency: Certain underlayments can help reflect heat and keep your building cooler.
• Extend your roof’s lifespan: By protecting the underlying structure and reducing wear and tear.

Choosing the right underlayment isn’t just a detail. It’s the foundation of a reliable, long-lasting roofing system.

Types of Underlayment for Metal Roofs

When planning a roofing replacement or new roof installation, there are three main types of underlayment that roofing contractors typically recommend for metal roofs:

1. Felt Underlayment

Felt, often referred to as tar paper, has been around for decades. It’s made from organic or fiberglass base saturated with asphalt.

• Pros:
  • Affordable and widely available
  • Provides a decent water barrier
• Cons:
  • Less durable over time, especially in extreme heat
  • Can tear or wrinkle during installation

Best for: Low-budget projects or temporary protection on metal roofs that don’t experience extreme weather conditions.

2. Synthetic Underlayment

Synthetic underlayment is made from polypropylene or polyethylene. It’s lighter, stronger, and more tear-resistant than traditional felt.

• Pros:
  • Highly durable and long-lasting
  • Resists mold, rot, and UV damage
  • Safer and easier for roofers to work on
• Cons:
  • Costs more upfront than felt

Best for: Homeowners or businesses looking for a reliable, long-term solution that withstands tough weather and the natural expansion of metal panels.

3. Self-Adhering (Peel-and-Stick) Underlayment

Peel-and-stick underlayment has a sticky back that bonds directly to the roof deck, creating a watertight seal.

• Pros:
  • Superior water protection, perfect for areas prone to roof leak repair
  • Provides an extra layer of defense in valleys and around penetrations
  • Excellent for preventing ice dam damage
• Cons:
  • Most expensive option
    Requires careful installation for maximum effectiveness

Best for: Coastal or high-humidity environments, or wherever maximum water protection is critical.

What Factors Should You Consider?

With rising material costs and a substantial investment in a new roof, choosing between metal roof underlayment materials can be a challenging decision. However, it’s essential to think beyond just the material. A reputable roofing contractor should be able to provide homeowners with sufficient information to make an informed decision. Some questions to help include:

• Climate: Will your metal roof be exposed to high winds, heavy rain, or intense sunlight?
• Roof slope: How steep is your roof? Some underlayments perform better on steeper or lower slopes.
• Building codes: What is required by your HOA or city? Local regulations may dictate certain types of underlayment.
• Budget: How much will it add to the cost of your roof installation? Higher-end underlayments cost more but can save money on repairs and maintenance in the long run.

Why Work with a Professional Roofing Company?

The right underlayment can make or break your metal roofing system, but it’s only as good as the installation.

Experienced roofing contractors understand:

• The best underlayment for your specific roofing type.
• Proper overlap and sealing techniques.
• How to integrate underlayment with metal panel expansion and contraction.
• Local codes and warranty requirements.

A metal roof can last 40 years or more, but only if it’s installed with the proper foundation. Choosing the right underlayment is an investment in your home or building’s safety, efficiency, and value. Don’t leave this critical step to guesswork; work with a certified roofer who knows the ins and outs of roofing maintenance and roof inspection.

About Modern Method Roofing

Installing a new metal roof on your Napa, CA, property? Need help selecting the right materials for your project? Modern Method Roofing is your trusted roofing contractor. Call (707) 255-8090 today for a personalized underlayment recommendation that’s built to last.