Every roofing system is composed of multiple essential layers of materials in addition to the obvious external roofing materials seen from the outside.

Underlayment is a component installed by roofers under the exterior materials for the critical role it plays in preventing leaking and the serious water damage that can occur when leaks are present.

Continue reading to learn more about the types and grades of underlayment used by residential roofers and why this unseen component is so important for every roofing installation!

What Is Roofing Underlayment?

Roofing underlayment is a protective sealant layer that roofers install under the shingles or other external roofing materials to protect everything beneath them.

Applied directly onto the roof decking, it provides a secondary moisture barrier under the exterior roofing that stops small leaks and drips that may get under the upper materials from reaching the more vulnerable decking.

As the external materials alone are not watertight, a layer or two of effective underlayment creates a safe watertight system when it is correctly installed.

What Types of Roofing Underlayment Are Available?

Residential roofers install protective underlayment over the decking of every roof regardless of the type of exterior materials installed on top of it.

There are two types of underlayment from which homeowners can choose for their homes:

Felt - Felt roofing underlayment rolls are made of fiberglass and paper felting which is saturated in asphalt to give it water resistance while still being breathable. It is available in two grades, standard 15# underlayment and thicker 30# underlayment, for installation on residential roofs. It is heavier than synthetic underlayment, but also less expensive.
Synthetic - Synthetic roofing underlayment rolls are made from synthetic polyethylene and/or polypropylene, which are both water-resistant. The synthetic underlayment used by roofers are more tear-resistant than felt and easier to install, but they are not vapor-permeable, requiring excellent attic ventilation to prevent issues with condensation moisture.

Why Is A Durable Underlayment So Important?

Underlayment is one of the most important components required for keeping any roofing installation watertight in different weather conditions.

It provides a durable surface onto which shingles, tiles, and even metal panels are installed to stop moisture from leaking or blowing under exterior components, especially in strong winds.

This essential moisture barrier prevents damage to the decking, which will rot after repeated exposure to moisture that can seep under the external roofing materials.

In regions that experience extreme conditions such as heavy rains, high winds, and hurricanes, residential roofers may be required to install multiple layers of high-quality underlayment to adhere to local building and roofing codes.

Additionally, a few layers of underlayment can provide a sound-deadening quality for metal roofing, making those installations quieter.

Get A Durable Installation with Quality Roofing Underlayment

Several layers of durable, high-quality roofing underlayment are critical for the effective performance of residential roof systems of all kinds.

The underlayment installed by professional roofers plays a key role in preventing water seepage around and under the exterior materials, protecting the decking and structural support system of the roof.

When the time comes to invest in a new installation, homeowners should work with an experienced residential roofer who can discuss different types of underlayment with them and install the one that will offer them superior moisture protection.