When most people think of roofs, they typically think of shingles or metal roofing. But what some may not know is there’s another layer of protection directly on top of the roof deck and under the roof covering that performs a critical role in protecting your home from moisture damage. It’s called roofing underlayment.
Contractors just like Spartanburg Roofing Company know the best type of roofing underlayment that will definitely suit your roofing material. This is also a very important aspect you should consider before your roofing installation. Find out more about this critical component to your roof’s structure.
What Is Roofing Underlayment?
Roofing underlayment is what lies between the shingles and the roof sheathing, or roof deck, which is typically either plywood or OSB. It’s installed directly on the roof deck and provides a secondary layer of protection from the elements, including rain, snow, and wind.
There are two main types of roofing underlayment:
- Felt
- Synthetic
Each product has its pros and cons, and the type you choose may depend on your geographical area, roofing materials used, roof design, budget and what your roofing contractor may suggest.
Felt Roofing Underlayment
Felt roofing underlayment is one of the oldest types of roofing underlayment. It’s created by saturating paper or fiberglass mat with asphalt.
Felt roofing underlayment is typically available in two types: No.15 felt and No. 30 felt. Compared to No. 15 felt, No. 30 felt is typically thicker, stronger, and may be less prone to tearing or ripping off during installation or weather events.
The main advantage of using felt roofing underlayment is cost. Felt underlayment tends to cost less compared to the synthetic underlayment, which is why it’s often the go-to for budget-conscious homeowners.
Synthetic Roofing Underlayment
For enhanced water-resistance and protection from the elements, many roofers are choosing to go the route of synthetic roofing underlayment. These products are usually made from long-lasting polymers, which provide added strength and longevity. This type of underlayment is typically moisture-resistant, and when it’s installed correctly, it offers better protection from the weather compared to felt.
Synthetic roofing underlayment materials are not standardized, so different manufacturers may make their products differently, and therefore may have different levels of performance. Be sure to do your research and talk with a trusted contractor who can help guide you in selecting the right roofing materials to protect your home.
Synthetic roofing underlayment also tends to be:
Lighter* – Up to four times lighter in some cases
Fast to install – Because there is more material per roll compared to felt (synthetic roofing underlayment comes in wider and longer rolls), it results in fewer trips up the ladder for your roofers, saving them time and perhaps helping the job move along faster. For instance, a typical 2700 square-foot home might require three rolls of synthetic underlayment compared to 14 rolls of No.30 felt to cover the same area.
Safe – Synthetic underlayment is also advantageous for worker safety — the surface of many synthetic roofing underlayments, including those offered by Owens Corning, features a variety of slip-resistant surfaces for enhanced walkability. It’s also usually well-marked with overlap guides and indicators of where fasteners should be placed, helping to improve consistency and accuracy during installation.
Moisture-resistant – Where felt products tend to absorb water, synthetic roofing underlayments are built to repel water. This is important for homeowners concerned about moisture infiltration, especially if they plan to leave the underlayment exposed for a prolonged period of time.
Because it’s made of plastic, synthetic underlayment is typically resistant to mold growth, a definite advantage over felt.