What Type of Underlayment is Best for Metal Roof

What Type of Underlayment Is Best for Metal Roof

When it comes to metal roofing, the type of underlayment you choose is critical. Different underlayment materials offer different levels of protection and longevity. But which one is best for your metal roof?

Felt underlayment is the recommended choice for metal roof panels. Made from either a natural or synthetic base and saturated in asphalt, it offers excellent water-resistance. It’s also less expensive, widely available, and easy to install.

However, felt has its downfalls too. It doesn’t last as long as synthetic underlayment and doesn’t respond well to high temperatures. It also needs protection from wind rips due to its flammability from the petroleum-based asphalt.

Why Felt is the Best Underlayment for Metal Roofs

What Type of Underlayment Is Best for Metal Roof 1

Felt underlayment is an essential component of any metal roof, providing an additional layer of protection from water and other elements. It is a cost effective material and a widely available option, making it the best choice for metal roofing.

Cost Effective and Widely Available

Felt underlayment is often cheaper than synthetic alternatives. In addition, it is one of the most commonly used materials in metal roofing, therefore it can easily be sourced from various suppliers.

Resistant to Water Damage

Felt underlayment is made from a natural or synthetic base that has been saturated with asphalt to make it water resistant. This ensures that any moisture from rain won’t seep through to the roof panels and cause long-term damage.

Protects Against Wind Rips

Wind rips can be highly damaging for metal roofs unless they are properly protected against them. Felt underlayment provides an extra layer of protection against these rips, keeping your roof secure during high wind speeds.

Low Flammability Rating

The asphalt used in felt underlayment helps to provide a low flammability rating, reducing the risk of fire damage to your home or property. This makes felt an ideal choice when it comes to safety as well as performance in metal roofs.

Effect of Climate and Environment on the Choice of Underlayment for a Metal Roof?

When choosing an underlayment for a metal roof, there are several factors to consider in relation to the climate and environment. These factors can vary greatly depending on the location of the building and the type of climate it experiences. Here are some key considerations:

Temperature and Moisture Levels

In areas with high levels of moisture, a waterproof underlayment is necessary to protect the roof from water damage that can be caused by rain and snow. Additionally, in places where temperatures fluctuate frequently, a temperature-resistant underlayment can help ensure the roof remains stable and does not expand or contract excessively, which can lead to damage over time.

Wind and Impact Resistance

In regions that experience high winds or frequent storms, choosing an underlayment that is designed to withstand strong gusts and impact damage is crucial. This type of underlayment can help prevent leaks and damage caused by fallen debris or branches.

UV Exposure

In sunny areas with high levels of UV exposure, choosing an underlayment with UV resistance can extend the lifespan of the roof. This is because UV exposure can cause the underlayment to break down and become less effective over time, leading to leaks and damage to the metal roof.

Environmental Impact

When considering an underlayment for a metal roof, it is important to also think about the environmental impact of the material used. Choosing an eco-friendly option can help reduce the overall environmental footprint of the building and contribute to sustainable construction practices. Additionally, choosing a recycled material can help reduce waste and limit the use of natural resources.

Cost and Durability

The cost of the underlayment and its overall durability are also important factors to consider when making a choice. While it may be tempting to choose a lower-cost option, investing in a durable and high-quality underlayment can save money in the long run by reducing the need for frequent repairs or replacement.

Pros and Cons of Using Synthetic vs. Traditional Underlayments for a Metal Roof?

Pros and Cons of Using Synthetic vs. Traditional Underlayments for a Metal Roof

Pros and Cons of Synthetic Underlayment

Synthetic underlayment is a newer technology that has quickly gained popularity due to its superior moisture resistance and durability. Here are a few pros and cons to using synthetic underlayment for your metal roof:


  • Moisture Resistance: synthetic underlayment is much better at protecting against moisture intrusion compared to traditional felt underlayment.
  • Durability: synthetic underlayment is much more durable than felt underlayment and can resist tearing and punctures. This means that it will not need to be replaced as often.
  • Lighter Weight: synthetic underlayment is much lighter than felt underlayment, which makes it easier to handle and install. This can save time and money.
  • UV Resistant: synthetic underlayment is usually UV resistant, which means it won’t break down as quickly when exposed to sunlight.


  • Higher Cost: synthetic underlayment is usually more expensive than traditional felt underlayment, which can add to the overall cost of installing a metal roof.
  • Not as Breathable: synthetic underlayment may not be as breathable as felt underlayment, which could lead to moisture buildup and potential problems down the line.

Pros and Cons of Traditional Underlayment

Traditional felt underlayment has been used for decades and is still a popular choice for many homeowners. Here are a few pros and cons to using traditional felt underlayment for your metal roof:


  • Cost: felt underlayment is typically less expensive than synthetic underlayment, which can help save on the overall cost of installing a metal roof.
  • Breathable: felt underlayment is more breathable than synthetic underlayment, which allows moisture to escape and helps prevent potential problems down the line.


  • Moisture Sensitive: felt underlayment is not as moisture resistant as synthetic underlayment, which makes it more susceptible to damage over time. This means that it may need to be replaced more often than synthetic underlayment.
  • Less Durable: traditional felt underlayment is less durable than synthetic underlayment and can rip or tear more easily during installation or maintenance.
  • Not UV Resistant: felt underlayment is not typically UV resistant, which means that it can break down more quickly when exposed to sunlight over time.

Ultimately, the decision between synthetic and traditional underlayment will depend on your specific needs and budget. While synthetic underlayment is generally considered to be more durable and moisture resistant, it may not be worth the higher cost for some homeowners.

Traditional felt underlayment may be a more affordable option, but it may not be as durable or moisture resistant as synthetic underlayment. Consider your specific situation and consult with a professional roofing contractor to determine the best underlayment for your metal roof.

Impact of the Cost and Durability of Underlayments on the Overall Value of a Metal Roof Installation

Impact of the Cost of Underlayments

The cost of underlayments can significantly impact the overall value of a metal roof installation. Underlayments are essential components of a roof system as they help protect the roof from elements such as water, wind, and heat. They act as a barrier between the roof and the interior of the building.

The cost of an underlayment can vary depending on the quality, material used, and the manufacturer. The cheaper underlayment may appear to be a cost-saving option in the short term, but it can greatly affect the roof’s durability and lifespan.

Cheaper underlayments may not hold up well under extreme weather conditions, and they may require frequent replacement, leading to additional expenses.

On the other hand, high-quality underlayments may cost more, but they are likely to last longer and provide better protection, hence increasing the overall value of the metal roof installation.

Impact of the Durability of Underlayments

The durability of underlayments is a crucial factor in determining the overall value of a metal roof installation. A durable underlayment can help prolong the lifespan of the roof and reduce the risk of damage and leaks. Metal roofs are known for their longevity, and using a reliable underlayment can help to ensure that the longevity is maximized.

A high-quality underlayment can withstand tough weather conditions better than lower quality ones. For instance, in areas prone to hurricanes or heavy rainfall, a durable underlayment is necessary to prevent water damage and leaks. Additionally, a durable underlayment can be more resistant to wear and tear that can occur during installation, so it is less likely to get damaged.

Overall, investing in a high-quality, durable underlayment is essential for maximizing the value of a metal roof installation. This can help ensure greater protection for the building and its occupants, better energy efficiency and cost savings over time, and increased property value.

Should You Use Underlayment on Metal Roof?

Using underlayment on a metal roof is always a great idea. It’s recommended by professionals and offers a variety of benefits. Whether you’re concerned about moisture or looking for extra insulation, underlayment has got you covered.

Of course, some folks might ask whether underlayment is necessary.

While it’s true that you can skip it, doing so means that you’re missing out on valuable protection for your home. Plus, why take the chance of damage or leaks when you can be proactive? Trust us, you’ll be glad you decided to use underlayment on your metal roof.

Do You Need a Vapor Barrier Under a Metal Roof?

Absolutely! If you want to prevent moisture from causing all sorts of problems like rot and mold, then it’s highly recommended to have a vapor barrier under a metal roof. Without one, water can build up in the walls and lead to long-term issues that will be costly to fix. It’s one of those things that you don’t want to take a gamble on, especially if you plan on keeping the property for any length of time.

Not only will a vapor barrier protect against moisture-related issues, but it will also help with the overall thermal performance of the structure.

It acts as an additional layer of insulation, which can help to reduce energy costs and keep things more comfortable year-round. It’s a simple addition that can have a big impact on the longevity and efficiency of your building. So, be sure to install a vapor barrier under your metal roof and reap the benefits for years to come.

Is Synthetic Roof Underlayment Better Than Felt?

Synthetic roof underlayment is definitely better than felt. It lasts longer and offers superior water-resistance, providing greater protection for the roof deck in the event of primary roofing material failure. Homeowners who invest in synthetic underlayment can enjoy peace of mind knowing that their roof is more durable and longer-lasting than those with traditional felt underlayment.

So, if you’re looking for the best possible roofing solution, synthetic underlayment is definitely the way to go.

Do Metal Roof Need OSB Under?

Yes, metal roofs do require OSB underlayment. While the metal roofing itself provides excellent protection against rain, wind, and other elements, it depends on the OSB as a sturdy base. Without the OSB underlayment, the metal roof cannot be properly secured to the house’s framing, which results in a weak roof that is prone to leaks, damages, and even complete failure in high winds or storms.

Installing OSB under metal roofing is essential for its structural integrity and longevity, ensuring a long-lasting and durable roofing solution that can withstand harsh weather and provide adequate protection for your home.

Do You Have to Have Sheathing Under Metal Roof?

Yes, you definitely need sheathing under your metal roof! It might be tempting to think that you can skip the underlayment to save some cash, but trust me – it’s not worth it. Using underlayment is a wise investment because it provides an extra layer of protection for your roof. By not using it, you’re setting yourself up for potential problems that could cost you even more down the road.

So be smart and don’t cut corners – put down that sheathing and give your metal roof the durable support it needs.

Does a Metal Roof Need Plywood Under It?

If you want to install a metal roof, it’s always best to use a roofing felt layer between the metal roof and the bare plywood. It’s an indispensable accessory because it protects the plywood from moisture and provides an additional layer of insulation. Some people also prefer to add an extra layer with a slip sheet to ensure that the felt sheet remains safeguarded.

Although it may be tempting to skip this step, it’s crucial if you want your metal roof to last for decades without any issues. So, to answer the question: yes, a metal roof needs plywood under it, but make sure to add the appropriate layers of roofing felt and slip sheet for optimal protection.

Frequently Asked Questions

What Needs to Go Under a Metal Roof?

When it comes to metal roofs, it’s important to have some sort of underlayment in place. Felt, self-adhering membrane, and synthetic sheet are the three most common options. Without any of these options, your roof is more likely to be damaged by the weather elements like wind and moisture.

So, what needs to go under a metal roof? Well, it depends on your personal preferences and budget. Felt is the most affordable option, but it doesn’t offer as much protection as the other two options. A self-adhering membrane is expensive, but it offers the best protection against the weather elements.

Synthetic sheet is the middle ground in terms of affordability and protection. Ultimately, the choice is yours, but remember that having an underlayment is important for the health and longevity of your roof.

Does Metal Roofing Require an Underlayment?

Metal roofing requires an underlayment, no doubt about it. But here’s the thing: you can’t just use any ol’ underlayment you would on an asphalt roof. Nope.

Metal roofing is special, and therefore the underlayment needs to be special too.

The issue with traditional underlayments is that the expansion and contraction of the metal roof wears down the integrity of the underlayment over time. So, what’s the solution? Felt and synthetic underlayments won’t cut it, but there are specialized underlayments designed specifically for metal roofing.

Don’t skimp on the underlayment for your metal roof – the right one could mean the difference between a long-lasting, quality roof and one that’s bound to fail.

What Do You Put Down Under Metal Roofing?

For metal roofing, the material used for underlayment is typically non-perforated, asphalt-impregnated felt underlayment. This is the traditional and most common choice for steep-slope roofs. The felt underlayment can come in various types, including organic reinforced and inorganic reinforced options.

The purpose of the underlayment is to provide an extra layer of protection between the roof deck and the metal roofing panels. It can also help with moisture control and improve insulation. Overall, the felt underlayment is a reliable and affordable option for metal roofing projects.

Can You Put Metal Roofing Directly on Plywood?

Putting metal roofing directly on plywood is not recommended. There are a variety of reasons for this, including the fact that metal roofing requires a solid, stable base in order to perform properly. Plywood does not provide the necessary stability for metal roofing, as it can warp, shift, or even rot over time.

Additionally, metal roofing can expand and contract with changes in temperature, which can exacerbate the problem of warping or shifting if the plywood is not strong enough to withstand such movements. In short, if you want to install metal roofing, you’re better off using a more stable and durable material as a base, such as OSB or even metal decking.

Do You Need Roofing Paper Under Metal Roofing?

Yeah, you need roofing paper under metal roofing. I mean, sure, you could save some cash by skipping this step, but it’s a risk. Plus, it’ll end up costing you more in the long run if you have to fix any problems down the line.

The thing is, the underlayment acts as an extra layer of protection.

It helps prevent things like ice and water damage, as well as leaks. So, even though it might not seem like a big deal, it’s definitely worth it to include this step. Trust me, your wallet will thank you later.

Read Also:


If you’re considering a metal roof for your home, it’s important to know the role of underlayment in the installation process. While some argue that underlayment may not be necessary because metal roofs are designed to be airtight, others believe it’s an important extra layer of protection. If you do decide to use underlayment, synthetic options like plastic film or polymer-based sheets may offer better longevity and resistance to extreme weather conditions than traditional felt.

The decision to use sheathing or plywood as a base layer for your metal roof ultimately depends on factors like the pitch of your roof and the type of metal panels you’re using. However, with proper installation and underlayment, your metal roof can provide exceptional durability and protection for years to come.

Why is Underlayment Important for Metal Roof Valleys?

Underlayment is crucial for metal roof valleys. It acts as a protective layer that prevents water infiltration, ice dam formation, and moisture damage. Metal roof valleys explained: without proper underlayment, leaks and corrosion can occur in these vulnerable areas, compromising the integrity of the entire roof.


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