The purpose of roofing underlayment is to serve as an additional barrier or protection for a roof. As the roof ages and is exposed to the harsh weather environments water may get under the shingles leaking into the building causing damage and wood rot. With an additional layer of protection the chances of this happening is reduced greatly.
Not too long ago just about every shingle roof was installed using felt paper as an underlayment between the roof deck and the shingles. Roofing felt paper is manufactured with infused asphalt or fiberglass allowing it to serve its purpose just fine. However, felt paper should not be exposed for too long after it has been installed as it is prone to tear and high winds can blow rain water under the gaps where the felt paper overlaps. Felt paper comes in large rolls and is installed horizontally at the bottom edge of the roof first with each addition row overlapping the row below it. This allows water to run off the paper and off the roof without access to the roof deck. When choosing your felt paper you basically have 2 main options to choose from, either 15-pound felt or 30-pound felt. Since 30-pound felt is thicker and stronger it is a much better choice. As mentioned, felt paper has served its purpose just fine for decades; however, there are new innovations with more durable roofing underlayment such as self-adhesive peel & stick.
Peel & Stick
Peel & Stick roofing underlayment composed of a rubberized asphalt waterproofing compound, reinforced by fiberglass making it much tougher and more durable than traditional felt paper. Peel & Stick is a self-adhesive modified composite underlayment allowing installers to simply roll it out, peel off the tape, and allow it to stick directly to the deck. Unlike traditional felt paper Peel & Stick creates a watertight barrier for the roof as it seals the deck and around the nails. In the event that a storm blows off a few shingles, peel & stick underlayment will stand up to the job waterproofing your home as wind and rain can’t be blown under the overlaps and run into the nail holes as with felt paper.
When installing shingle roofs with felt paper we typically use Gorilla Guard EVERFELT 30 manufactured by Atlas Roofing Corporation. For our customers that choose to have peel & stick installed on their shingle roof we typically use Polystick IR-Xe which is manufactured by Polyglass. We are able to install any type of underlayment by all major roofing material manufactures and can work with you to find what will be the best fit for your roof and budget.