Underlayment, or roofing felts, is an important component of sloped roofing systems. It serves as the second line of defense against water infiltration, in case the outer roofing layer fails. In this blog, the residential and commercial roofing contractors at Mobley Brothers Roofing & Restoration shares an in-depth look at this unseen yet essential roofing component.
How Underlayment Works
On a typical sloped roofing system, you will find the underlayment sandwiched between the outer roofing material (asphalt shingles or metal) and the roof deck. The seams are sealed using waterproofing material with adhesive backing, then mechanically-driven nails are used to fasten it to the deck. Roofing manufacturers design their own underlayment to match their roofing system requirements.
The roof’s underlayment should prevent rainwater from leaking into the layers below, in the event that the outer material is damaged or torn off. While it does protect the roof from water infiltration, it’s not a substitute for the outer roofing material. Certain underlayment products also let the roof deck “breathe,” by letting moisture from the roof deck evaporate.
Types of Underlayment
Residential and commercial roofing contractors offer different types of underlayment:
- Asphalt-Saturated Felts — This is also known as “traditional” felts, and is made with recycled paper and fabric, soaked in asphalt. The resulting material is very similar to tar paper. Asphalt-saturated felts adds stiffness to the roof deck and improves its impact resistance.
- Rubberized Asphalt — Despite its name, rubberized asphalt is essentially sheets of rubber, and contains only a small amount of asphalt. This elastic material is ideal for use in regions that experience extreme temperatures. This is the only type of underlayment that is adhered to the roof deck or substrate instead of fasteners.
- Non-Bitumen Synthetic Underlayment — This is the type that’s widely used on today’s sloped roofing systems, and is made of synthetic material such as polyethylene or polypropylene. The resulting material is strong, elastic, and moisture-repellent.
Mobley Brothers Roofing & Restoration is your leading provider of residential and commercial roofing services. Give us a call at (615) 906-1195 or fill out our contact form. We serve customers in Knoxville and Lebanon, TN.