Types of Steep Slope Roofing Underlayment

Primary roofing materials are the main layer of protection that shield a home from the elements and most significantly water intrusion.  This can include roofing materials such as; Asphalt Base Shingles, Metal Roofing, Clay & Cement Tiles, Cedar Shakes and Synthetic base look alike roofing profiles. All steep slope roofing structures should include a secondary layer of protection that many homeowners are not as familiar with known as roofing underlayment!

What is roofing underlayment and what is its role?

Roofing underlayment is a water resistive barrier membrane that is commonly installed under the primary roofing material.  This membrane acts as a secondary layer of protection for the OSB or plywood roof deck against water or moisture intrusion  It also helps to provide nail sealability for fasteners used to attach the primary roofing products. Acts of Mother Nature and aging products can cause interior leaks and water damage. A properly installed, good quality underlayment could prevent expensive water damage repairs or replacement.

There are several types of steep slope roofing underlayment materials but most can be grouped into three main categories:

  1. Black Asphalt-saturated felt (also referred to as traditional roofing felt)
  2. Mechanically attached synthetic underlayment
  3. Self-adhered underlayment (often called Peel & Sticks Ice and Water Barrier and Ice Dam Barrier)


Black Asphalt-saturated Felt

Historically, Roofing felt has traditionally been one of the most common types of underlayment used for residential, steep slope and other applications. It is produced by impregnating paper or in incorporating fiberglass mat with asphalt. This produces a semi water resistant material or membrane that is commonly used in roof construction.  The term “Felt” comes from the historical method of making the base material. Felt is made from recycled paper in large rolls supplied in different thickness in common widths.


 #30 Felt after 3 months UV exposure 

In the past, primary benefit of Black Asphalt Roofing Felt was low cost and its ability to repel water and seal around fasteners. Felt is susceptible to blow-offs, tears and absorbs water with extended life, making it even weaker and a serious safety hazard during installation. Synthetic underlayments have dropped in cost to that of felt. The lower cost of synthetics has attracted wider acceptance from roofing contractors who previously considered synthetics as a “premium roof only” product. The lower cost and ease of installation using synthetics has exposed fact that oil saturated felts are; much heavier, come in smaller rolls, and are more time consuming to install.  Felt may decline in performance in combination with heat and extended time under the primary roof. Even more importantly, the new synthetic underlayments are stronger and more durable, particularly important if the project demands the underlayment be left exposed to the elements for a period of time. Roofer’s aside, today’s homeowner’s also benefit from synthetics. Safer walking surfaces reduce liability and most synthetics underlayments have printed warranties. Most felt products do not come with a warranty at all. In comparison, All Titanium Synthetic Underlayments have a Lifetime Limited Warranty.

Self-Adhered Synthetic Roofing Underlayment normally consists of a polyolefin facer combined with a bitumen or butyl combination thereof, a pressure sensitive adhesive, plus a release liner on the very bottom (liner is removed during installation). The adhesive is designed to provide adhesion to the roof deck as well as a waterproof seal around fasteners during the initial installation. During the roofing initial installation, the main purpose for this product category is to provide roofing structures with an enhanced secondary layer of protection for primary roofing materials.  This is especially important for critical areas of the roof such as eaves, ridges, valleys, dormers and skylights. The addition of an adhesive to the membrane provides increased protection from wind-driven rain, water, snow and ice dams.   A self-adhered underlayment like Titanium PSU30 also offers a slip resistant walking surface on the facer that reduces fatigue and provides for a safer working environment for installers. Titanium PSU30 also offers a self-sealing lap system that increases overlap adhesion strength by providing direct bitumen to bitumen adhesive contact. Titanium PSU30 also has a crinkled split release liner which saves the installer time due to ease of removal.

PSU30 offers the only LifeTime Limited Warranty to align with that of primary roofing purchased.


Titanium’s UDL30 is a highly engineered, mechanically attached, coated woven synthetic roofing underlayment for sloped roofs. UDL30 possess a revolutionary patented slip resistant Sure-Foot® nodular walking surface technology that allows for easier steep slope walk-ability, even in wet conditions. It can be used under Asphalt Base Shingles, Metal Roofing, Clay & Cement Tiles, Cedar Shakes and Synthetic base look alike roofing profiles.

Mechanically Attached Synthetic Roofing Underlayment

Synthetic underlayment is commonly made by coating both sides of a strong inner polyolefin woven or nonwoven membrane with varying layers of polyolefin coatings to produce a water resistant product.  Each layer constitutes a different contributing feature for optimum performance. Roofing contractors continue to convert in large numbers from felt to synthetic underlayments making this one of the fastest growing segments.


Titanium offers PSU30 which is modified rubberized asphalt Peel & Stick with a tough, rugged, SureFoot slip resistant patented nodular surface with a very unique self-sealing lap system.  It’s a professional grade 45 mil self-adhesive roofing underlayment with the advanced ice damming protection for use under: Asphalt Base Shingles, Metal Roofing, Clay & Cement Tiles, Cedar Shakes and Synthetic base look alike roofing profiles.

Synthetic underlayments are lighter, stronger, and more durable than felt.  They come in longer and wider rolls, which mean faster installs with less laps and seams per job.  If synthetic underlayments are installed correctly their exceptional durability and UV resistance to be left exposed to the elements for long periods, in a few cases up to 6 months without suffering from blow-offs and tears like asphalt saturated felts. Synthetics also lay flat and will not absorb water and wrinkle like felt, nor do they dry out, leach oils in the heat, or become stiff, difficult to roll or crack in the cold.

Furthermore, synthetic underlayments often include a special top surface treatment that makes the product safer to walk on and more slip resistant. Titanium UDL products offer a patented nodular walking surface called Sure-Foot® that allows for easier steep slope walk-ability, even in wet conditions.

TITANIUM offers a variety of high quality synthetic roofing underlayments to protect your home and other structures. For more information visit: http://www.interwrap.com/Roofing/


 Titanium UDL30 on roof with Titanium PSu30 installed in the eaves to prevent ice damming

When deciding on which underlayment to put on your roof, be sure to consider one that will maximize your roof’s life expectancy.

All data and information appearing on this site is anecdotal in nature, reflecting the contributor’s personal experience and not fact-based research and, therefore, to be used for information purposes only. Read full disclaimer