What Underlayment Is and Why It’s a Game-Changer for Your Home
The Parts of a Roofing System
A roof isn't just a layer of shingles nailed to wood. It is a highly engineered system where every component has a specific job. Shingles may get all the spotlight, but there’s a whole system of unique materials hard at work below the surface:
- Roof Decking (Sheathing): The structural foundation of your roof. Your roof decking is the sturdy wooden boards (usually plywood or OSB) that are attached directly to your home's rafters.
- Roof Underlayment: The unsung hero! The roof underlayment is a secondary, water-shedding protective layer installed directly on top of the roof decking, right beneath the shingles. It’s made up of two separate parts, which cover different parts of your roof:
- Ice & Water Barrier (Leak Barrier): Helping to prevent leaks caused by wind-driven rain and ice dams, this protective covering is found around the edge of the roof (at rake edges & hips), and anywhere there’s a penetration like a chimney or a skylight, as well as in roof valleys and, importantly, on all eaves.
- Roof Deck Protection: Helping to shield the roof deck from moisture infiltration, this layer is the important water barrier between the wood decking and the shingles. Roof Deck Protection is usually either synthetic membrane or asphalt-saturated felt; differences between the two are listed below.
- Shingles (or Outer Roof Covering): The outermost layer that you can see from the street, shingles make up the most recognizable part of your home’s defense against Mother Nature’s punishing UV rays and unpredictable, extreme storms.
- Flashing: Metal pieces installed around joints and valleys (like around chimneys or vents) to prevent water from seeping into the most vulnerable gaps.
What is The Purpose of Underlayment On My Roof?
Think of roof underlayment as your roof's backup insurance policy. Even if a brutal storm manages to rip away a shingle or blow rain sideways, the underlayment is there to stop that water from soaking into your wooden roof deck. Without it, trapped moisture can quickly lead to mold, mildew, and rot, all of which lead to costly interior water damage.
Underlayment generally comes in two main styles:
- Asphalt-Saturated Felt: The traditional option, often reinforced with fiberglass (like GAF Shingle-Mate®) in order to help it lie flat and resist wrinkling when exposed to moisture.
- Synthetic Materials: Modern, high-performance options made from tough plastics or polypropylene (like GAF Tiger Paw™ or FeltBuster®). These are incredibly durable. They resist tearing, won't rot, and offer excellent slip-resistance for the crews working on your roof. Some premium versions, like GAF Deck-Armor™, even feature breathable technology to let trapped moisture escape while keeping outside rain out.
Ready to Tackle Your Roof Repair?
To ensure all of these layers—from the decking and underlayment to the shingles and accessories—are installed seamlessly, you need the right experts on your side. Whether you require a total overhaul of your roofing system or you’re in need of repairs, reach out to our friendly professionals at Roof Rite Exteriors. Our team delivers the elite craftsmanship and dedicated service needed to keep your exterior envelope in great shape for decades to come.