09 Nov

Anatomy of a Roof System: Roof Underlayment

Your Roof Needs Some Underwear

Pardon our familiarity, but we’re talking about your roof’s underlayment—what’s between your shingles and roof decking. This material is installed underneath your shingles but right on top of the roof deck. This layer is the meat in the roofing sandwich, protecting your home from ice, snow, heat, and wind. It’s yet another way to shore up your roof for years to come.

Anatomy of a Roof System Roof Underlayment - Peak Roofing and Construction


What Are My Roof Underlayment Choices?

There are two types of roof underlayment: felt and synthetic. Let’s take a look at each of them.

1. Felt: Breathable and Affordable

FeltThis option is created by saturating paper or fiberglass mats with asphalt. Basically, it’s tarpaper and has been around for a long time. There are two types within this category: No. 15 and No.30. The latter (No. 30) is less prone to rip or tear.

The Pros 

  • Economical. It costs less, compared to synthetic. For those watching their budget, this is a great option.
  • Breathable. Even though it’s water-resistant, it’s still breathable, which is a plus if you have asphalt shingles. It’ll add to the longevity of your roof.
  • Common tools. Ordinary tools are used for installation. Nothing fancy required.

The Cons 

  • Might tear. It’s prone to tearing if it’s windy and might also tear during installation.
  • Water affects it. If the material gets too wet, it can wrinkle the felt, which makes it more difficult to create a seamless, smooth surface for the other roof materials that are installed on top and underneath to adhere to.
  • Heavy. It’s a bit harder for contractors to carry rolls of it up a ladder and onto your roof. Sure, the contractors might be pretty strong, but lugging these around in the heat might well slow things down, especially in Texas heat.
  • Slippery. Could pose a hazard during installation.


Synthetic: Strong and Water-Resistant

Synthetic:  This one is made from long-lasting polymers. However, they’re not standardized, which means each manufacturer has its own way of making them.

The Pros 

Tough and extremely durable. It’s resistant to UV and moisture, as well as foot traffic, while the other roof layers are being installed. It also stands up over time.

Fast to Install. The rolls are wider and longer—and lighter—so contractors spend less time hauling them up and down from the roof, which makes the job move along more quickly.

Safer. Felt is a bit slick, aka slippery. Synthetic material is slip-resistant and is usually well-marked with overlap guides to show where the fasteners should be placed.

Repels water. If there’s a pause during roof installation, this feature is great because it helps keep water from getting into the attic, the walls, and your interior walls. But neither felt or synthetic aren’t water-proof – they simply thwart the amount that gets in.

The Cons

Not cheap. You can find synthetic underlayment for a variety of prices. But generally speaking, it’s more costly than felt. However, it does a good job of keeping water from seeping into your roof. Protecting it from moisture over time is critical.


We’ll Be Brief(s)

You’ll likely have issues if the materials that make up your roof aren’t strong, quality products. Peak’s here to help. All you have to do is call or email us, and we’ll be there for you. We even guarantee our work. In fact, we like to think we beat the pants off the competition.


Be sure to read the next article in our series: Anatomy of a Roof System: Roof Drip Edge

Jeff Riss

Jeff has 20 years of sales experience, a love of roofing, and a strong entrepreneurial spirit. He leads Peak Roofing & Construction’s team but also is known for getting his hands (and knees) dirty on a job site. His passion for customer service, integrity, and quality craftsmanship drives his success. Peak Roofing & Construction is a family-owned, locally-operated business focused on doing things the right way. His deep understanding of roofing, gutters, windows, fences and exterior painting provide a strong foundation for running the business and serving his customers.

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