What is the best underlayment for a low sloped metal roof?

The best underlayment for low slope metal roofs is a self-adhering membrane underlayment. This type of underlayment is specifically designed for low-slope roofing applications.

How long can underlayment be exposed?

Exposure times vary for type of underlayment material and product. It’s always best to cover your roofing underlayment as soon as possible. For more information on underlayment exposure time, contact Dream Roof.

Can I install my metal roof underlayment DIY?

While it is possible to install metal roofing underlayment on your own, it’s best to consult a professional roofing company such as Dream Roof. Installing underlayment without prior experience can lead to unintended damages, and in some cases, void your warranty.

Are roof underlayments waterproof?

Most underlayment materials are water-resistant rather than waterproof. However, some synthetic underlayment materials are virtually waterproof. Check with the manufacturer or your roofing contractor for more information.

What happens if you don't use underlayment on a metal roof?

Without proper underlayment in place, your roof becomes more vulnerable to water seepage and damage. This includes leaks, mold and mildew development, as well as roof deck rot.

How To Choose the Best Underlayment for Your Metal Roof

Roof underlayment is a beneficial addition to metal roofing. It provides you with an added layer of protection from water intrusion, moisture build-up, and extreme weather. However, there are many types of underlayment to choose from and determining which one is right for you can be difficult.

In this article, we’ll explore everything you need to know about underlayment, including what it is, when it’s necessary, common types, and contractor approved products. Read on to learn more about the best underlayment for metal roofs.

What Is Roof Underlayment?

Metal roof underlayment is a water-resistant barrier that’s installed underneath your metal roofing. It’s attached to the roof deck or sheathing, and provides an added layer of protection against water and moisture infiltration. Without the underlayment, your home is more vulnerable to extreme weather, including wind, rain, and snow.

Determining which type of underlayment to install will depend on many factors, such as your local climate and personal budget. The most common types of roofing underlayment are synthetic, felt, and self-adhering membrane. Choosing the right underlayment is vital to the longevity, effectiveness, and durability of your roof.

Is Underlayment Necessary for Metal Roofs?

Yes, roof underlayment for metal roofs is highly recommended. In addition to protecting your home from water and moisture, underlayment also helps prolong the lifespan of your entire roofing system. The underlayment safeguards the roofing materials from the negative effects of melting snow, heavy rainfall, humidity, UV rays, and ice dams.

Common Roofing Underlayment Materials

A metal roof is a significant investment. It’s therefore vital to make sure it has a strong support system that aids in the protection and safety of you and your home. Felt, synthetic, and self-adhered underlayments are the most common types of underlayment. Each comes with its own set of advantages and disadvantages. Learn more about each underlayment, including their pros and cons, by reviewing the following:

Felt Underlayment

Also known as felt paper, asphalt felt, and tar paper, felt underlayment is a common material used for steep-sloped metal roofs.

Here are the advantages and disadvantages of felt underlayment for metal roofs:

Advantages

Felt underlayment is the most affordable type of underlayment, with the average cost ranging from $0.05 to $0.50 per square foot. In comparison to self-adhered and synthetic underlayment, felt is the most budget-friendly option.

Asphalt-soaked felt underlayment effectively repels moisture. It’s specifically designed to prevent water from penetrating the surface, which would otherwise damage the underneath wood sheathing.

Felt underlayment has been around for decades. It’s simple to install as it doesn’t require any complex tools. Felt underlayment is also readily available as it’s a widely used underlayment material.

Disadvantages

Compared to other materials, felt underlayment has a very low heat-resistance. It cannot endure exposure to temperatures of 180°F and higher for long periods. At 200-220°F, the asphalt can begin to warp and soften, losing its structural integrity.

While synthetic and self-adhering underlayment can last 35+ years, felt underlayment typically only last between 12 and 20 years. The felt underlayment will reach the end of its lifespan long before your metal roofing, which can last 40 to 70 years.

During installation, felt underlayment will need to be covered immediately to prevent UV and heat exposure. Prolonged exposure can cause the underlayment to wrinkle, crack, and/or dry out before the metal panels have been installed.

Self-Adhering Underlayment

Self-adhering membrane underlayment, also referred to as an ice and water barrier, protector, or shield, has a peel-and-stick design which allows it be directly applied to your roof decking. It typically has a butyl-based or rubberized asphalt base and s mounted to a polyethylene carrier sheet.

Here are the pros and cons to self-adhering metal roofing underlayment:

Advantages

Self-adhering roof underlayment can endure temperatures of 260- 300°F. This means that even throughout the hottest of summers, you can have peace of mind knowing your underlayment will maintain its adhesive bond and water-resistance.

The adhesive backing of self-adhering underlayment makes it highly resistant to wind uplift. It forms an airtight seal that increases its overall strength and durability. A s a result, there are no air leaks and your home’s energy efficiency is improved.

There’s no need for heavy equipment, specialized tools, or fasteners such as nails, screws, or staples. The process involves peeling back the adhesive backing and firmly sticking the underlayment to the roof decking.

Disadvantages

While self-adhering underlayment has great heat-resistance, does not respond as well to cold temperatures. Cold weather can reduce the effectiveness of the bond, leading to leaks and moisture infiltration.

Self-adhering underlayment cannot withstand long-term UV ray exposure as effectively as felt and synthetic underlayment. Self-adhering underlayment needs to be installed quickly once it’s been unwrapped.

Once the adhesive has been applied, it’s difficult to adjust its positioning. Self-adhering underlayment therefore requires precise installation by experienced roofing professionals. Repositioning the self-adhering underlayment can cause it to peel up over time.

Synthetic Sheet Underlayment

Synthetic underlayment includes polyethylene or polypropylene that’s woven or spun together with a polymer. This creates a protective shield between the metal roofing and the deck.

Here’s a list of synthetic sheet underlayment advantages and disadvantages:

Advantages

Synthetic roof underlayment has an average lifespan of 25 to 50 years. Its strength, high-temperature resistance, and UV resistance make synthetic underlayment incredibly durable, thereby prolonging its lifespan.

Synthetic underlayment is designed to endure temperatures of 260°F and higher. This makes it one of the best materials for metal roofing, which can reach extremely high temperatures.

Synthetic underlayment typically meets or exceeds Class A fire ratings. This is the highest fire resistance rating for building materials, which indicates minimal flame spread and smoke development.

Disadvantages

With increased durability, fire-resistance, and temperature tolerance comes higher prices. On average, the cost of synthetic underlayment ranges between $0.17 and $0.55 per square foot.

Synthetic underlayment requires specialized equipment and installation techniques. It’s vital to have synthetic underlayment installed by licensed and experienced roofers to avoid tears and punctures.

Although water-resistance is an advantage, synthetic underlayment is virtually waterproof. As it creates a vapour barrier between the metal roofing and the decking, roofs become more susceptible to trapping moisture.

Popular Underlayment Products for Metal Roofs

Below, you can explore popular underlayment products that are used and trusted by contractors and professional roofers. Review them here:

Felt Underlayment Products

The following is a list of the top felt underlayment products, including their benefits:

FeltBuster® Synthetic Felt Roofing by GAF: Manufactured by GAF, this felt underlayment is ideal for locations that are prone to harsh weather. Benefits include a lifetime warranty, 90-day UV degradation resistance, and advanced durability.
CertainTeed #30 Asphalt Saturated Underlayment: This product is thicker, stronger, and more secure than other felt underlayments. Some of the various benefits include easy roll-out, highly visible alignment lines, and appropriate breathability.

Self-Adhered Underlayment Products

Here are a couple of the most popular self-adhering underlayment, along with their advantages:

Owens Corning WeatherLock® Specialty Tile & Metal: This self-sealing underlayment effectively blocks water intrusion around roofing penetrations such as fasteners. Advantages include 180-day UV resistance, slip resistant non-woven polyester, and a 30-year limited warranty.
Titanium® PSU30: This durable self-adhering underlayment, made from modified rubberized asphalt and a synthetic facer, creates a secure and flat barrier under metal roofing. A few of the top advantages include its Sure-Foot® nodular walking surface, 180-day UV ray resistance, and limited lifetime warranty.

Synthetic Underlayment Products

Here are two commonly used synthetic metal roof underlayment products, including their advantages:

Owens Corning ProArmor®: ProArmor® has up to 12 time more strength and 450% more coverage than felt underlayment. Benefits of using this product include 90-day UV ray resistance, high-temperature rating for metal roofing, and a 10-year limited warranty.
RhinoRoof® U20: The RhinoRoof® U20 is known for its exceptional wind resistance and durability. The advantages of choosing this synthetic underlayment product include a FiberGrip surface, 20-year limited warranty, and 90-day UV ray resistance.

FAQ’s

What is the best underlayment for a low sloped metal roof?
The best underlayment for low slope metal roofs is a self-adhering membrane underlayment. This type of underlayment is specifically designed for low-slope roofing applications.
How long can underlayment be exposed?
Exposure times vary for type of underlayment material and product. It’s always best to cover your roofing underlayment as soon as possible. For more information on underlayment exposure time, contact Dream Roof.
Can I install my metal roof underlayment DIY?
While it is possible to install metal roofing underlayment on your own, it’s best to consult a professional roofing company such as Dream Roof. Installing underlayment without prior experience can lead to unintended damages, and in some cases, void your warranty.
Are roof underlayments waterproof?
Most underlayment materials are water-resistant rather than waterproof. However, some synthetic underlayment materials are virtually waterproof. Check with the manufacturer or your roofing contractor for more information.
What happens if you don't use underlayment on a metal roof?
Without proper underlayment in place, your roof becomes more vulnerable to water seepage and damage. This includes leaks, mold and mildew development, as well as roof deck rot.