Best Underlayment for Metal Roofs: Homeowner’s Guide to Synthetic vs. Felt vs. Ice and Water Shield
A high-performance metal roof is more than just the panels.
It’s a complete system designed to protect your investment, lower your bills, and keep your home looking great for decades to come.
Underlayments are an essential piece of that system.
They sit under the metal panels for added water-shedding protection throughout the life of your roof.
Done right, you’ll virtually never have to think of them again once your roof is finished. But if they’re not done right, you could see premature leakage and damage.
This guide gives you a clear breakdown on which underlayment works best for metal roofs. Plus we cover where ice and water shield belongs, and what homeowners should insist on seeing spelled out in a roofing quote.
Quick answer: What’s the best underlayment for a metal roof?
For most homes, the best approach is a quality synthetic underlayment across the main field of the roof, combined with self-adhered ice and water membrane at leak-risk areas like eaves, valleys, and penetrations.
The exact “best” setup depends on your roof design, climate, slope, and manufacturer instructions, but this combination works well for many homeowners gathering bids today.
Underlayment vs. ice and water shield vs. vapor barrier
These terms get mixed up constantly, and that confusion causes bad bids and bad installs. Clearing this up helps you ask better questions.
Underlayment is the secondary water-shedding layer installed over the roof deck and under the metal panels. It provides temporary weather protection during install and backup protection long-term.
Ice and water shield is a self-adhered, peel-and-stick membrane. It seals around fasteners and protects the most vulnerable areas where water can back up or be driven under the roof covering.
A vapor barrier is different. It controls moisture movement inside the building assembly and is not the same thing as roofing underlayment.
Local codes and manufacturer instructions often dictate where ice barriers are required and how they must be installed, which is why installers reference ICC Digital Codes when designing roof assemblies.
The three underlayment types homeowners will see in metal roofing quotes
Most metal roofing proposals reference these three categories. Knowing what each one does (and doesn’t do) helps you compare bids fairly.
Felt underlayment
Felt is the traditional asphalt-saturated paper many homeowners recognize. It still shows up as a budget option or when specified for certain applications.
Its drawbacks are worth understanding.
Felt can tear more easily, wrinkle if it absorbs moisture, and generally does not last as long as modern synthetics under metal roofing systems. It can work, but it leaves less margin for error.
Synthetic underlayment
Synthetic underlayments are now the go-to choice for many metal roofing contractors. They are lighter, stronger, and more resistant to tearing and wrinkling during installation.
For many homes, synthetic underlayment is a strong default choice for the main field of the roof because it installs flatter and stays stable under metal panels.
Self-adhered membrane (ice and water or peel-and-stick)
Self-adhered membranes are designed for high-risk zones. They seal tightly around fasteners and provide extra protection where water concentrates.
In colder or wind-exposed regions, code language around ice barriers often points toward self-adhered membranes or layered approaches in critical areas, again referencing standards published by ICC Digital Codes.
Nu-Ray Metals offers felt, synthetic, and self-adhered underlayment options, but the right choice for your home should always follow roof design, climate, and manufacturer guidance.
Where each underlayment belongs on a metal roof
Underlayment performance is as much about placement as it is about material. Even the best product fails when used in the wrong location.
The field of the roof
The field is the broad, open area of the roof plane. This is where a synthetic or specified underlayment is typically installed.
The key detail is that it must lie flat and smooth. Wrinkles or buckles can telegraph through metal panels and affect appearance and performance.
Eaves and edges
Eaves are a common failure point. Wind-driven rain and ice dam backup put pressure on this area first.
Ice barrier requirements vary by region, so this is where local code and manufacturer guidance matter most. In many climates, self-adhered membrane at eaves is a smart and often required upgrade.
Valleys and transitions
Valleys concentrate water flow. Small mistakes here turn into big problems quickly.
That is why self-adhered membranes are commonly used in valleys, transitions, and roof-to-wall intersections to provide extra sealing and redundancy.
Penetrations
Pipes, skylights, chimneys, and wall transitions succeed or fail on detailing. Underlayment choice matters, but flashing matters more.
A good quote specifies both the membrane used and the flashing method—because one without the other is incomplete protection.
Climate and roof-design factors that change the “best” choice
There is no universal underlayment recipe. These conditions should shape the conversation with your contractor.
Heavy rain or wind exposure:
Focus on clean sequencing, secure attachment, and reinforced edges. Ask how underlayment is protected during installation.
Snow and ice-dam risk:
Ice barrier placement matters more than material brand. Ask exactly how far the membrane extends at eaves and why.
Coastal exposure:
Watertightness depends on the entire system with underlayment, trims, sealants, and fasteners working together. Ask how corrosion resistance and detailing are handled throughout the roof assembly.
Low slope or complex roofs:
Details matter more than product names. Ask how valleys, transitions, and slope changes are layered and sealed.
Homeowner problems caused by the wrong underlayment (and how to prevent them)
Problems usually trace back to shortcuts, not materials.
- Wrinkles under metal panels can affect appearance because the underlayment was not installed flat or compatible with the system.
- Blow-offs and tears happen when products are pushed beyond their intended exposure limits.
- Misplaced membranes lead to overspending in low-risk zones and under-protection where it actually matters.
- Condensation confusion arises when underlayment is blamed for ventilation or assembly issues it cannot solve alone.
Clear specs and expert installation prevent all of these.
What to demand in your metal roof quote
A strong quote reads like a plan, not a placeholder.
It should clearly state the underlayment type and exactly where it will be used. It should spell out where peel-and-stick membrane will be installed and how far it extends. It should describe how penetrations and transitions are detailed, not just say “flashings included.”
Ventilation scope and change-order triggers should be defined up front. If these details are missing in some bids, you can’t compare them on equal footing.
Underlayment FAQs to help homeowners decide
What is the best underlayment for a metal roof?
For many homes, synthetic underlayment on the main roof field combined with ice and water shield at eaves, valleys, and penetrations works best. Climate, roof design, and manufacturer requirements ultimately decide what is correct for your home.
Is synthetic underlayment better than felt for metal roofing?
In most cases, yes. Synthetic underlayment is stronger, more tear-resistant, and lays flatter under metal panels. Felt can still be used, but it leaves less margin for installation errors.
Do you need ice and water shield under a metal roof?
Often, yes—especially at eaves, valleys, and penetrations. Many cold or wind-exposed regions require ice barriers by code, and self-adhered membranes are commonly used to meet those requirements.
Where should peel-and-stick membrane go on a metal roof?
Typically at eaves, valleys, roof-to-wall transitions, and around penetrations. These areas see the highest water exposure and benefit most from self-sealing membranes.
Can the wrong underlayment cause condensation under a metal roof?
Underlayment alone does not cause or fix condensation. Moisture issues usually stem from ventilation, insulation, and roof assembly design—not just the underlayment choice.
Can you reuse old underlayment when replacing a metal roof?
In most cases, no. Old underlayment may be damaged, incompatible with new systems, or no longer meet current code or manufacturer requirements.
What should underlayment look like in a roofing quote?
It should name the material type, specify where each product is used, and explain how critical areas are detailed. Vague language makes it impossible to compare bids accurately.
Next step: get the right underlayment for your roof and climate
When underlayment is specified correctly, it stays invisible and unnoticed.
And that is exactly how you want it.
If you are actively collecting bids, now is the time to lock down underlayment details, not after panels are on the truck.
Nu-Ray Metals supplies multiple underlayment options and works through a network of knowledgeable dealers who understand how roof design and climate affect performance. Use their dealer resources to confirm the right approach for your home before you sign a contract.
Click here to find a dealer close to you.
