What Goes Under Metal Roofing?

What goes under metal roofing? Well, it depends on different factors. Where you live, your climate, budget, and more. Find out more!

When replacing your existing roof with a metal roof, you’re going to be able to take advantage of so many benefits. Metal roofs are highly fire-resistant, have long life spans, and come in all kinds of shapes and colors. 

There are several different options for what goes under metal roofing, so you can choose for yourself and your home. When picking out a roof, though, you will need to decide what goes under it. Here’s what you can put under the roof and how to choose the suitable material. 

How Underlayment Affects Your Roof

There’s no doubt that metal roofs are some of the best at keeping the elements out of your home, but they need the proper underlayment to do the job best. There are different types available to you, as what works in your area and climate won’t work in another. That’s why it’s essential to choose carefully. 

The underlayment should be chosen on how well it can provide a barrier against:

• Water
• Heat
• Air
• Vapor

As you’d imagine, you’ll have different needs depending on where you live. 

All these things will affect the lifespan of your roof. For example, if water is allowed to get into the roof and cause problems, or if there isn’t proper air filtration, it will need repair and even replacement sooner than it should. 

In some cases, you may not need underlayment. For example, structural metal roof panel systems are designed to sit on supports without a roofing deck. As such, they don’t require underlayment as there isn’t a substrate to attach it to. 

You’re most likely picking a metal roof as they’re known to be the longest-lasting in mind. You’ll be paying a reasonable premium for that life span, too. With that in mind, you need to choose what goes under your metal roofing to give you the most protection for your roof. 

Types Of Metal Roof Underlayment

There are three main types of roof underlayment. Here’s what you need to know about each of them, so you can see which is right for you. 

Felt underlayment: 

This is the most common type of underlayment used under metal roofs. The felt is usually non-perforated and asphalt-impregnated, although there are several types that you can choose. Talk to your roofer, as they’ll have a recommendation for you. 

For example, you can choose between organic or inorganic reinforced felt. Inorganic felt is usually reinforced with glass fiber and usually lies flatter and stands up better than other types of felt. 

Felt will work best in arid climates, as they don’t offer a lot of protection against air and water vapor migration. That doesn’t mean that it can’t be used in a cold climate, though. It’s most often used with ice dam barriers to help stop them from forming. 

Synthetic sheet underlayment: 

This kind of underlayment, as the name suggests, is made from various types of plastics. They are made from polyethylene, polyolefin, or polypropylene. Each sheet can be anywhere from 8 to 30 mils thick. 

Most synthetic sheer underlayment is vapor resistant, although it doesn’t count as an air barrier. They are most commonly used as an alternative to the self-adhering membrane, as it’s a cheaper material. It’s something it keeps in mind if you’re looking for ways to lower the budget. 

This kind of underlayment is also susceptible to wind damage, so it may be what you’re looking for in your roof if you get high winds. It’s also less sensitive to cold weather installation, so it works well as an option in colder climates. 

Self-adhering membrane underlayment: 

This is the final type of underlayment to consider, and it’s usually the most expensive. It’s usually made of rubberized asphalt or butyl-based adhesive with a polyethylene carrier sheet. 

These sheets are perfect for both cold and hot climates, as they have properties that help both. In cold climates, they can be used as ice dam protection in roof eaves and valleys. In warmer climes, they stand up well to temperatures up to 240ºF without melting, as other types of underlayment can do. 

As the name implies, these sheets are made to be peel and stick and are stuck directly to the roof deck when installed. As they stick to the substrate, they are a sound air barrier. They’re also vapor impenetrable. 

Which Underlayment Should You Choose?

As you’ve seen, there are a few different options for what goes under metal roofing. The one you choose will depend on your needs. Here’s what to keep in mind when choosing:

Your climate: 

This is the most significant factor when it comes to your roof. The weather will affect what you need, so you’ll need to choose carefully. For example, in a wet climate, you need something effective at keeping moisture out. 

Your budget: 

This is another crucial deciding factor. Your new roof is a real investment, and you’ll need to put work in to decide how much you want to spend. While more expensive options are often better, you’ll need to think about whether they will give you what you need. For example, the less costly synthetic sheet underlayment provides better protection against wind, so keep that in mind. 

What Goes Under Metal Roofing: Final Thoughts

If you’re still not sure about which one is right for you, then you should talk to your roofing team. They will be able to recommend the best one for you. They are the experts, so they should have some good ideas for you. 

Now you know what goes under metal roofing, just how vital underlayment is for your metal roof,  and why you’ll need to pick the right one for your home. Use this guide to understand what’s out there, and talk to your roofer to see which one would be best. With the suitable material, your metal roof will be protected and be able to last for decades to come.