What is the Best Underlayment for Metal Roofs?

Underlayments are designed to lay under metal roofs and provide thermal protection as well as waterproofing solutions for your home. Without them, metal roofs tend to be loud when it rains, cold during the winter, and hot during the summer with the raging sun and high temperatures. There’s no question that you should have one under your roof, but the question you should be asking is: Which roofing underlayment should you choose?

At Legacy Service, we wrote this article to help you decide which one would be best for your home. Of course, you should also schedule a consultation with an expert so that they can walk you through your options and provide you with advice on how to proceed with your roofing installation or roofing replacement. Call us at 215-798-9790 or contact us here.

What is Roof Underlayment?

Underlayment is a vapor barrier or water-resistant material that’s put under metal roofing and installed directly onto the roof deck. It’s applied under all of the other materials, and it provides an extra layer of protection against extreme weather conditions. The three main types of underlayment for metal roofs include felt, synthetic sheet, and self-adhering membrane.

Without an underlayment, the roof and rest of the home are exposed to the elements, which include not only wind and moisture but also chemicals and resin. Finding the best underlayment for your metal roof is essential to maintaining the health of your home throughout its lifespan.

Does My Metal Roof Need an Underlayment?

Yes, your metal roof will need some type of recommended underlayment. Without it, you’ll most likely end up dealing with an assortment of problems, including entrapped moisture and roof leakage, both of which can accelerate the deterioration of your roof. Your underlayment should also match the lifespan of your metal roofing system to ensure its longevity.

One of the advantages of metal roofs is the fact that they can last for about 40-70 years! They have superior durability and can withstand all types of weather, from harsh winds to rainstorms and blizzards. Take care of your metal roof and it will take care of you.

Underlayment Materials

At Legacy Service, we’d like to help you find the best underlayment product for your standing seam metal roof. In this section, we’re going to review each of the three main types so that you can figure out what underlayment to use for your building. We’ll give you an idea of the pros, cons, and average prices of each type.

To schedule a roof replacement consultation with one of our professionals, please feel free to give us a call at any time at 215-798-9790. We’ll schedule an appointment where we can go over your options and find the one that will work best for you.

Felt Underlayment (Asphalt Felt/Tar Paper Underlayment)

Known by many different names (including felt paper, roofing tar paper, and asphalt-soaked felt), felt underlayment is the most commonly used type of underlayment material on steep-slope metal roofs.

Pros: Homeowners choose felt because:

• It’s less expensive than the other types.
• It’s water-resistant, which helps keep water from penetrating the surface if any of it leaks through the roofing structure.
• It’s commonly used, so it’s readily available nearly anywhere.

Cons: Its disadvantages include:

• It doesn’t last as long.
• It may not respond well to high-temperature environments.
• It doesn’t have the best recyclability.
• There may be better options for low slope metal roofs.

Price: The cost for felt underlayment will typically be the least expensive out of the three main types.

Synthetic Sheet Underlayment

Synthetic underlayment for metal roofing is a newer innovation that has been taking over the industry in recent years. It’s made by weaving/spinning together polyethylene or polypropylene and a polymer to form a protective barrier to put between the roof deck and the material.

Pros: Homeowners decide to go with synthetic sheet underlayment because:

• It typically has a longer lifespan than felt underlayment.
• It’s more durable because it’s developed with thermoplastic polymers that are more resistant to tearing, moving, and other types off damage.
• It has a tolerance for high temperatures.

Cons: The disadvantages of synthetic sheet underlayment include:

• It’s more expensive than felt underlayment.
• It has a low permeability rating (which is good for keeping out moisture), but that will also make it more difficult to have proper ventilation.

Price: The cost of synthetic sheet is typically more expensive than other types, including felt.

Self-adhering Membrane Underlayment

Self-adhering membrane underlayment is a peel-and-stick product that’s designed to adhere to a roof deck. It consists of either a rubberized-asphalt or butyl-based adhesive with a polyethylene carrier sheet.

Pros: People choose self-adhering membrane because:

• It’s effective for ice dam protection in places like roof eaves, rising walls, valleys, and dormers.
• It can provide protection in environments that reach high temperatures, even as high as 240ºF.
• It can serve as an effective air barrier material since it’s fully adhered to the substrate.

Cons: The disadvantages of self-adhering membrane include:

• If it’s an inferior product and not installed properly, it runs the risk of being peeled back.
• It can have poor performance in low temperatures.

Price: Insurance companies may offer a discount for properly installed self-adhered membrane underlayments.

Frequently Asked Questions About Underlayment

As a local roofing contractor, we get asked a lot of questions about metal roofing and underlayment. There are many different types, from breathable underlayment for metal roofing to waterproof underlayment to titanium underlayment. We answered some of your most frequently asked questions here. Take a look to see if we’ve answered yours!

Is underlayment necessary for a metal roof?

In simplest terms, yes, you should use underlayment with your metal roof. It might not be absolutely necessary, but it is highly recommended, especially because metal roofing is notorious for being cold in the winter, hot in the summer, and loud when it rains. High winds may also affect your roof. Fortunately, adding underlayment will provide an extra layer of protection for your home, and it will improve everything from insulation to waterproofing.

If you need help deciding on a type of underlayment that would work for your home, don’t hesitate to ask our team at Legacy Service.

What underlayment is best for a metal roof?

There are three main types of underlayment for metal roofs. They include felt, synthetic sheet, and self-adhering membrane. Although there is no superior type, we’d like to help you find one that works best for you since they each have their own advantages and disadvantages. We’ve included some of the pros and cons in the sections above under “Underlayment Materials,” but it’s best to consult a professional to determine which type would actually be best for you.

At Legacy Service, we’ve been in the industry since 2005, and we’ve helped a countless number of customers install or replace their roof and build the home of their dreams.

Do you need an ice and water shield under metal roofing?

If you live in an area that gets cold in the winter and sees plenty of precipitation throughout the year, then you probably should install an ice and water shield under your metal roof. For most roofing projects, two types of underlayment are needed, the first being an ice and water shield. This underlayment is made of either a rubberized-asphalt or butyl-based adhesive with a polyethylene carrier sheet, and it has an adhesive backing with a peel and stick feature. The product you choose should be able to withstand high temperatures and can be used with metal, tile, and other roofs with a scrim-reinforced top surface.

Do you need a vapor barrier under a metal roof?

Vapor barriers are used to reduce the amount of condensation that can move through a material. When they’re installed properly, they can help reduce any problems that you have with condensation as well as air leakage on fiberglass-insulated walls. Without one, water can get trapped in the wall, which will produce moisture and ultimately other issues like rot, mold, and trouble with thermal performance. Vapor barriers are recommended for under metal roofs.

Do metal roofs have underlayment?

Underlayment for metal roofs may not always be required, but it is strongly recommended. Underlayment is a water-resistant barrier that provides an extra layer of protection from the elements as well as several other advantages. These advantages include enhanced insulation, an even surface for roof installation, compliance with building codes, and a quality noise barrier.

Can you put metal roofing directly over shingles?

It depends on the circumstances, but in many cases, you will be able to install metal roofing directly over shingles. Metal is surprisingly lightweight considering how strong it is, so adding a metal roof over shingles will not significantly increase the overall load on your home’s structure. However, you may not be able to if you already have multiple layers of shingles. You’ll also need to check with your local building and zoning departments to make sure they approve.

Do metal roofs need furring strips underneath?

Furring strips are best described as long, slender strips that are constructed from wood or metal. They’re usually 1” x 2” or 1” x 3” in size and can be applied both vertically and horizontally. If you’re installing a metal roof over another roof, you will need furring strips. Make sure you correctly space the furring strips to decrease the amount of condensation. Common spacing is 24 inches.

Can you put tar paper under metal roofing?

Tar paper, or asphalt-saturated felt underlayment, has historically been the go-to choice for roof underlayment. However, a few challenges are associated with this type of underlayment. First, since it’s usually available in 2 or 4 square rolls, it can take many rolls to complete an average-sized roof. The installation can also be difficult because this underlayment tends to buckle and wrinkle. Lastly, it’s important to know that as a paper product, the material can degrade quickly. If you’d prefer, there are other underlayment options available.

Can you put a metal roof over plywood?

A metal roof should not be installed directly over bare plywood, but it can be installed over plywood once there are protective layers in between. A felt moisture barrier over the plywood is the bare minimum; a slip sheet should also be installed to protect the felt sheet from potential damage from the metal roof.

Can you put metal roofing directly on rafters?

Yes, a metal roof can be installed directly over rafters. Since corrugated metal panels are relatively lightweight, they can fit almost any type of situation. You can install the roof with or without insulation, but installing rolled insulation is usually a good idea because it can help keep the inside of the building at a comfortable temperature.

Which Underlayment Should You Choose?

You might have a good idea of which underlayment you should use after reading this blog. If so, that’s great! The next step is to contact your local roofing experts to schedule a consultation, so you can tell them exactly what your wants and needs are, and they can suggest what they think will be the best type for you and your home.

At Legacy Service, we can be that local roofing contractor that answers all of your questions and completes your roofing installation or replacement project for you. We’ve helped thousands of customers over the years, from New Hope, PA to Brick, NJ, and beyond! We’re also a member of both the National Roofing Contractors Association (NRCA) and the National Association of the Remodeling Industry (NARI). Learn more about roof installation and replacement by calling us at 215-798-9790 or contacting us here.