The underlayment is the secondary barrier that protects the roof deck from moisture, in case the outer roofing layer fails. Here’s what makes underlayment a crucial component of any residential roofing system.
How Does Roofing Underlayment Work?
The roofing underlayment is a sheet of material that goes between the decking and the outer roofing, for example, sheet metal or asphalt shingles. There is more than one type of underlayment – we will go into more detail below – but its purpose is the same: protecting the roof deck in case the outer roofing is punctured, damaged or torn off.
During installation, the underlayment is fastened to the roof deck using fasteners with gaskets that help prevent water infiltration, even at the seams. This creates a monolithic barrier over an entire roof plane. It’s important to note that the underlayment is meant to protect your roof against water infiltration and not serve as a second roof. This means you still need to call for roof repair in case the roof is damaged.
Types of Underlayment
The following are the types of underlayment that can be used on sloped roofs:
Asphalt-saturated felts are also known as “traditional” underlayment because these were the first types that were ever used on roofs and are commonly known as “felts”. It’s basically sheets of pulped fabric and recycled paper soaked in hot asphalt, which makes it stiffer and more impact-resistant than other types of underlayment.
Despite the name, rubberized asphalt contains only a small amount of asphalt; it’s mostly made of rubber. Its elasticity is ideal for use on homes located in extreme climates. Unlike other types of underlayment, rubberized asphalt is installed on the roof deck using adhesives.
Non-bitumen synthetic underlayment (or simply, “synthetic underlayment”) is the most common type of underlayment. It resembles tarpaulin, but it has other properties that let the roof deck “breathe” and allow moisture to evaporate instead of trapping it under.
Ultimately, the right kind of underlayment should complement the roofing material. Your roofing contractor can help you choose the right options, including complete roofing systems offered by roofing manufacturers.
Pressure Point Roofing Eugene, LLC is your leading provider of roof maintenance and installation services. Give us a call at (541) 688-7663. You can also fill out our contact form to schedule an appointment. We serve customers in Springfield as well as the surrounding communities in Oregon.