Because of their durability, longevity, low maintenance requirements, and other advantages, metal roofs have become a frequent option for households and businesses.
However, there are many aspects to consider when choosing a metal roof to fit your needs, so it’s no surprise that some parts get ignored in the process.
One of them is the metal roof underlayment.
To start working on your roofing needs, contact your local roofing pros for FREE ESTIMATES!
Does Metal Roofing Require An Underlayment?
Due to its many benefits, people often think that metal roofs don’t require underlayment and skip installing this component.
Metal roofs are also quite costly, so looking for ways to spend less money for their installment is a valid reason.
However, while it might seem like an unnecessary expense, underlayment for metal roofing is of great importance and offers numerous benefits for your home.
Underlayment is placed between the decking and the metal tiles and acts as an additional layer of protection against weather elements such as rain, snow, hail, and wind.
It allows the water to slide off the roof and prevents leakage into the building.
During cold months it helps keep the warmth inside and lowers heating losses.
In regions with hot summers and high humidity, the underlayment keeps the heat outside and prevents condensation from collecting between roofing elements.
In addition, underlayment acts as a soundproofing barrier and reduces the noise caused by weather elements.
Underlayment not only protects after its installment, but it also serves as a temporary solution against climate conditions during construction.
If the roof on your new home can’t be installed right away, underlayment can last between two and 30 months as a replacement.
Did you know? If you want further protection, you can place a slip sheet on top of the underlayment. The sheet protects the underlayment material and prevents tearing during weather changes since the metal roof is prone to expanding and contracting.
See costs in your area
Start Here - Enter Your Zip Code
What Underlayment Should Be Used Under Metal Roofing?
While the underlayment for your metal roof will depend on several factors, such as the weather conditions and the building code in your area, it is always good to explore the available options.
You can choose from several types of underlayment for metal roofs.
Felt Underlayment
Felt underlayment is also known as felt paper, tar paper, and asphalt-saturated felt.
It is the most frequently used material for underlayment due to its affordable price.
It is typically made from wood or fiberglass coated with asphalt.
Synthetic Underlayment
Synthetic underlayment is a more recent type of underlayment that has become the preferred choice for households nationwide.
It’s made of synthetic materials, such as polypropylene or polyethylene.
It usually comes in rolls and is mechanically attached.
High-Temperature Underlayment
High-temperature underlayment is specifically made for metal roofing in regions with extremely warm weather.
It is typically made from rubberized asphalt material reinforced with a fiberglass mat.
Peel-and-Stick Underlayment
Peel-and-stick underlayment is also called self-adhering membrane underlayment.
In principle, it is a type of synthetic underlayment that doesn’t require any additional tools such as a stapler or roofing nails.
The materials used in this type of underlayment vary by manufacturer, but it typically has at least three layers: the waterproof layer, the adhesive layer, and the release paper layer.
The first layer is similar to the synthetic underlayment made from polypropylene or polyethylene.
The adhesive layer is an asphalt-based or butyl-based material that sticks to the decking. The last layer is a thin paper or plastic sheet that covers the adhesive to prevent it from sticking to other surfaces before installation.
Metal Roof Underlayment Average Cost
The price of underlayment for your metal roof will depend on your location, the size, type, and additional parts of your roof, as well as on the type of underlayment you choose, the number of layers, brand, and weight.
On average, the material cost is only $0.40–$0.70 per square foot.
Together with installation costs, the average price is $1.50–$3.50 per square foot.
The slope of your roof will affect the amount of material required to cover your roof. For example, a flat roof will have less surface area than a steep roof on the same size house.
For an average, 2,000-square-foot roof, this price would be between $600 and $1,600, depending on the underlayment material.
If you need to replace the old underlayment with a new one, the process is more complicated, and the average price goes up to $4 per square foot.
Keep in mind that while replacing the underlayment, some of the roofing material might get slightly damaged, which adds additional cost.
Pro Tip: If you want to install underlayment for your roof for a lower price, wait for the end of fall or the beginning of winter, as it’s a less busy season for contractors. The service and the materials might be cheaper than they are during more active seasons. Furthermore, when calculating the budget for your underlayment installment, add around 10% of the price on top if your roof has dormers, curbs, hips, etc.
Metal Roof Underlayment Cost Breakdown
| Material | Average Cost of Material per Square Foot | Average Cost per Square Foot With Installation |
|---|---|---|
| Felt Underlayment | $0.15-$0.30 | $0.25-$0.45 |
| Synthetic Underlayment | $0.30-$0.50 | $0.40-$0.60 |
| High-Temperature Underlayment | $0.50-$1.50 | $0.70-$1.20 |
| Peel-and-Stick Underlayment | $0.50-$1.50 | $0.65-$1.00 |
Felt Underlayment
Felt underlayment is less expensive than other materials and costs between $0.15 and $0.30 per square foot.
Together with the installation cost, this price is between $0.25 and $0.45.
Synthetic Underlayment
Synthetic underlayment is slightly more expensive, with its price falling between $0.30 and $0.50 per square foot.
With added installation cost, it would be $0.40–$0.60.
High-Temperature Underlayment
The price range for high-temperature underlayment is $0.50–$1.50 per square foot.
With installation cost, the cost range increases to $0.70–$1.20.
Peel-and-Stick Underlayment
Similarly to high-temperature underlayment, peel-and-stick underlayment costs $0.50–$1.50 per square foot.
The installation cost raises this number to $0.65–$1.00.
Metal Roof Underlayment Requirement
In addition to choosing suitable underlayment material and finding a good contractor, the underlayment for your metal roof has to comply with the building code of the area where the installation will occur.
Since metal roof underlayment offers valuable protection from weather elements, some regions require all buildings to install them.
They might also need or recommend specific materials and installation methods.
Installing Metal Roof Underlayment
Hiring a contractor is a good decision if you have no experience with roofing or aren’t confident in your skills.
On the other hand, unnecessary labor and installation costs can significantly increase the price of your project, and hiring an unreliable and untrustworthy roofing contractor can cost you a lot more money in the future.
Before choosing a roofing contractor, make sure to get several quotes (at least three) and read reviews from other people or get recommendations from friends and family.
In addition, ask how long they’ve been in the business and if they’re licensed, bonded, or insured.
Check if they have experience with your type of roof and ask for past references.
Look at their warranty details, additional costs, installment time, and if they have all the necessary permits.
If you decide to install the underlayment on your own anyway, make sure to follow the local building code, take safety precautions, and prepare the necessary tools.
Although the installment process differs depending on which material you use, there are some general steps to follow for all metal roof underlayment installments.
- Remove old and other roof elements. Clean the decking of any dirt, dust, and nails, and make sure it’s dry. If you’re using a peel-and-stick underlayment, leave it in the sun and let it uncurl before you start.
- Inspect the decking for any rotten, moldy, or damaged areas. Repair what can be repaired or replace them if the damage is too significant.
- Unroll the underlayment horizontally across the roof, starting from the bottom, and work your way up to the top. Ensure that it’s perfectly aligned with the edges of the roof. Leave at least 2 inches hanging over the eaves unless you use the peel-and-stick underlayment.
- Fasten the underlayment with roofing nails or staples according to the manufacturer’s instructions. The recommended space between the nails is 12 inches. Overlap the rows by at least 6 to 8 inches for better protection against moisture.
- If you’re using an underlayment with an adhesive layer, lay the side with the adhesive towards the roof and peel the paper layer from the upper half. Press the underlayment down with a hand roller or your hands as you unpeel. Pull the rest of the paper layer from underneath. When you reach the roof’s peak, remove the paper before laying down the underlayment strip.
- Seal the seams between each row with roofing cement or tape.
- Install flashing around chimneys and vents to prevent further moisture infiltration.
- Install the metal panels according to the manufacturer’s instructions.
Pro Tip: If your underlayment requires fasteners, make sure to choose nails or clips that won’t leave an imprint on the metal tiles when you place them on top and in case someone steps on it.
Who Sells Metal Roof Underlayment?
You can find metal roof underlayment in home improvement stores like Lowe’s, Menards, and Home Depot, a roofing contractor, or a metal roofing supplier.
Expect the prices to differ between companies since they have different expenses.
Best Underlayment for Metal Roof
The best underlayment for your metal roof will depend on factors such as your climate, your local building codes, and the type of metal roofing that goes on top.
Generally, the synthetic peel-and-stick underlayment is considered the best because of its durability, longevity, and low permeability.
However, they can be pricey, so consult a professional to find the best underlayment for your metal roof that fits your budget.
Who Makes the Best Metal Roof Underlayment?
Some of the best synthetic and peel-and-stick metal roof underlayment manufacturers are Kirsch Building Products, Owens Corning, FT Synthetics, GCP Applied Technologies Inc., Epilay Inc., and Continental Materials Inc.
Pros And Cons Of Metal Roof Underlayment
Metal roof underlayment is undeniably a necessary component of your roofing.
However, different materials used for underlayment have advantages and disadvantages, so let’s look at some of them.
Felt Underlayment
Pros
- Inexpensive
- Good for steep-sloped roofing
- Readily available everywhere due to its common use
Cons
- Doesn’t endure high temperatures
- Has a shorter lifespan than other materials
- Poor choice for low-sloped roofing
- Comes in small rolls, which increases installation time and cost
- Absorbs a lot of heat due to its dark color
- Not fire resistant and easily flammable
Synthetic Underlayment
Pros
- Has good durability and longevity
- Lightweight, comes in larger rolls, and is easy to handle and install
- Has good resistance to tears and punctures
- Tolerates high temperatures
- Doesn’t absorb a lot of heat due to its lighter color
Cons
- More expensive than felt underlayment
- Requires experience for its installation
- Low permeability requires good attic ventilation, so moisture from the inside doesn’t accumulate and cause molding
- Often not biodegradable
High-Temperature Underlayment
Pros
- Can withstand temperatures up to 250 degrees Fahrenheit
- Best for hot and humid climates
- Has good durability and longevity
Cons
- Can be more expensive than other materials
- Requires experience to install
- Only necessary for metal and tile roofing
Peel-and-Stick Underlayment
Pros
- Has good longevity and durability
- Endures high temperatures well
- Lightweight and easy to install
- Doesn’t absorb a lot of heat due to its lighter color
- Doesn’t require additional equipment to be attached to the deck
Cons
- More expensive option than other materials
- Has poor performance in low-temperatures
- Might peel off if not properly installed
- Not suitable for steeper-sloped roofs
When To Use Metal Roof Underlayment
Although using underlayment for metal roofs is recommended, it is not necessary for every building.
However, there are several cases when investing in a metal roof underlayment might save you a lot of trouble and money in the future.
- Low-sloped roofs: Since rain can’t escape quickly from flatter surfaces, roofs with a slope of less than 3:12 are at a higher risk of water leakage. Underlayment acts as an additional layer of protection against rainfall.
- Hailstorm areas: Large hailstones can dent or pierce the roof in regions with frequent hailstorms. Underlayment can reduce this impact.
- Windy areas: While metal roofs are an excellent choice for windy areas, they can be lifted by high winds. Underlayment can help hold the roofing in place and prevent damage to the metal panels.
- Humid climates: Condensation often happens on metal roofs in hot climates. Underlayment acts as an additional protection against moisture.
- Noisy environments: A lot of rain, hail, and other weather elements can make a lot of noise when they hit a metal roof. Underlayment can act as a soundproof layer and reduce the level of noise.
When To Replace Metal Roof Underlayment
The lifespan of metal roof underlayment can vary depending on the type of underlayment, installation, and climate conditions the roof is exposed to.
The average lifetime of a felt underlayment is 15 to 20 years, while a synthetic underlayment can last up to 40 years.
Extreme weather conditions can shorten the underlayment’s lifespan.
If the underlayment shows signs of damage or wear – such as punctures, tears, mold, rust, curling, shrinking, or wrinkling – it will require replacement sooner.
Consulting with a professional can prevent these problems from leading to even more significant issues.
Doing regular roof inspections can increase the underlayment’s lifespan by three to five years.
In addition, when replacing the roof, make sure to replace the old underlayment. You can only inspect the decking after removing it, and placing new underlayment on top of the old one can lead to severe problems later on.
Can I Use Synthetic Underlayment Under A Metal Roof?
Both synthetic and felt underlayment can be used for metal roofs.
Do You Put Plywood Under A Metal Roof?
Usually referred to as sheathing, plywood is used as decking under the roof. It acts as a base for other roof materials that go on top.
If your roof interior is well protected from moisture, the metal roof can be directly attached to the roof structure without plywood.
However, adding plywood together with the underlayment provides extra protection against weather elements and can prevent leaks for a longer time.
Plywood prevents condensation that happens when the warmth of your home meets the cold metal roof.
It also gives additional sound insulation and makes roof replacements more effortless in the future.
Plywood is lightweight and easy to install, which makes it an excellent choice for roofing applications.
The average cost of a 4 x 8 sheet of plywood ranges between $70 and $100.
Plywood can last more than 100 years unless exposed to moisture from both sides.
It is time to replace the decking if the wood is spongy, has a strange color, is moldy, is broken in some spots, or if case there are plumbing problems around the decking.
Pro Tip: Never install other roof elements over a wet decking, as the water might evaporate under the sun and make tiny holes that will allow future leaks.
Conclusion
If you have already opted for a metal roof, don’t miss out on its benefits – invest in a good metal roof underlayment.
It will not only protect your home from water infiltration, mold, draft, and energy losses, but it will also give additional support to your metal roof and protect other roofing elements.
Take your time choosing the proper metal roof underlayment for your home or building.
Get quotes from multiple contractors, consult a professional, check your local building code, and determine what roof underlayment is best for the weather in your location.
See costs in your area
Start Here - Enter Your Zip Code
For over 20 years Leo has run a successful roofing business in New England, specializing in metal roofing, as well as cool flat roofing technologies. Having replaced and installed hundreds of roofs in New England, Leo has first hand experience with pretty much every residential roofing material and roofing manufacturer available in the US.
