Chris Robinson Florida State Roofing Contractor 941-773-7883 Licence # CCC1326399

Underlayment Applications

Underlayment Applications



There are three basic types of underlayment used beneath roofing materials:

Felt underlayment may be made from either organic or fiberglass substrate, although the organic is much more common. It's called "organic" underlayment because it has a cellulose base


Various types of rubber-like materials are also used as underlayment and are generally referred to as “rubberized asphalt.” These typically have adhesive on one side, which is protected by a peel-off membrane, making them self-adhering. The rubber-like qualities of these underlayments make them self-sealing, meaning that they seal well around fasteners, such as staples and nails.

Rubberized asphalt underlayments are manufactured to meet different requirements:

They may be formulated for use in high-temperature situations. Some underlayments are designed to resist heat up to 250° F without degradation of the adhesive. This allows them to be installed under metal roofs an in harsh environments.

The asphalt may be polymer-modified.

Polymer-Modified Bitumen

The terms "modified bitumen" is often used when referring to asphaltic roofing materails. Sometimes, this term is shortened to "mod-bit." The term "bitumen" is a generic name applied to various mixtures of hydrocarbons. One of these mixtures is the asphalt used in underlayment, asphalt shingles, and built-up roofing. It's a common term in the roofing industry.

To improve various characteristics such as strength and elasticity, bitumen is sometimes modified using polymers which give it plastic-like or rubber-like properties, depending on which process is used.

Polymers are materials made of molecules which are custom-designed to give the material specific properties. Polymers are used in many different types of roofing products to increase their resistance to damage and deterioration.

You may also hear the term “cross-linked polymer” used. Molecules in cross-linked polymers actually bond to each other at the atomic level; they actually share atoms, which greatly increases the strength of the material.