Are you considering metal roofing? Do you want the highest-quality metal roof to make your investment worth it?
Investing in the best materials and components ensures your metal roof’s life is maximized. And one of the most important components is the underlayment.
The most important thing is your metal roof gets it in the first place. However, the best underlayment specifically for metal roofing is different from standard asphalt shingles.
For over 30 years, Bill Ragan Roofing has helped homeowners understand the complexities of the roofing industry. Because metal roofing requires something different, let’s dig into the best type of underlayment for a metal roof.
First, I’ll quickly break down what roof underlayment is and why it’s important. After that, you’ll learn the best underlayment for a metal roof, how it should be properly installed, and how much it costs.
What is roof underlayment?
Underlayment is a crucial roofing component used to add a waterproof barrier between the decking and main roofing material. It’s installed directly over the decking for extra protection and acts as the last line of defense to prevent water from entering your home.
(Synthetic underlayment)
There are two different types of underlayment: felt and synthetic.
Felt underlayment comes in 15 lb. and 30 lb. rolls, with the 30 lb. option being thicker, stronger, and less likely to tear than 15 lb. The big problem with felt is that it absorbs and holds water.
Synthetic underlayment is made out of woven/spun polyethylene or polypropylene. Unlike felt, synthetic wicks water and is easier to work with for installers.
While felt underlayment has been around longer, I always recommend synthetic underlayment to homeowners getting a new roof.
What is the best underlayment for a metal roof?
Felt and synthetic underlayment are great options for asphalt roofs, but as I said metal roofing is different. Metal roofing expands and contracts, which destroys the integrity of the normal types of underlayment as the metal panels go back and forth.
So, metal roofing needs high heat ice and water shield as underlayment over the decking. While this is a huge upgrade compared to normal underlayment, the cotton-like fibers won't stick to the metal panels as they expand and contract.
(Top: Before installation with underlayment; Bottom: After installation)
This prevents the underlayment from being destroyed and ensures the decking is protected if water gets under the panels. While metal roofing’s underlayment must be high heat ice and water shield, it’s also used with premium roof systems (synthetic, cedar shake, and slate).
Just know this type of ice and water shield is not used as underlayment for normal asphalt shingles. Instead, ice and water shield is installed in or around leak-prone areas for increased protection.
How do you properly install underlayment on a metal roof?
I always recommend hiring a qualified local roofing contractor with the right experience to install a metal roof. But no matter if you're a DIY homeowner or about to invest a lot of money in metal roofing, it’s crucial that high heat ice and water shield is installed correctly.
Lock strips are the first thing installed when getting a metal roof. They hold (lock) the metal panels on the roof edges (eaves and rakes) to prevent wind from getting underneath and lifting them.
The high heat ice and water shield must be installed over the lock strips at the eaves and under them at the rakes. If this isn’t done correctly, condensation will get behind the lock strip at the eaves, leaving streaks on the fascia and eventually rotting it out.
Once the fascia is rotted, you’ll have a roof leak in your walls or at the gutter line. You won't have to worry about this if you hire a roofing contractor with experience installing metal roof systems.
How much does metal roof underlayment cost?
Roofing prices fluctuate constantly and even vary depending on the area where you live. So, it’s impossible to give you an exact cost number.
However, I can at least give you a general idea of the budget you’ll need for high heat ice and water shield when getting a metal roof. High heat ice and water shield will cost around $125.00 per square (100 square feet).
For comparison, granular or sand ice and water shield starts at $50.00 per row of material, while smooth ice and water shield costs around $100.00 per square (100 square feet of roof area). But remember, it’s used as the underlayment for a metal roof in this situation.
This will be very expensive and is actually one of the big reasons why a metal roof is much more expensive than asphalt shingles.
What other components and materials make up a metal roof?
Now you know the best underlayment for a metal roof, how to install it properly, and an idea of how much it costs. If you do get a new metal roof, be sure to ask the roofing contractor if they’ll be using high heat and ice and water shield.
Even if they say yes, making sure your estimate mentions it is also important. However, underlayment is just one crucial part of a metal roof.
There are plenty of other important components and materials that all come together like a puzzle to form a full roof system. So, it’s crucial to know everything else you’ll be paying for when getting a new metal roof.
That’s why I wrote another article breaking down the 7 components and materials of a standing seam metal roof system.
Check out 7 Materials That Make Up a Standing Seam Metal Roof to learn the other crucial components of a metal roof.
