New ASTM Standard Replaces Felt Standards for Qualification of Synthetic Underlayments - April 2021

Wed, Apr 07, 2021

Why Synthetic Underlayment?
Roofing contractors are always looking for ways to do their job more efficiently and to provide product choices that they feel improve the quality and durability of the installed roof. Asphalt felt underlayments, also referred to as “felt paper” or “tar paper,” have served the roofing industry well for decades. However, there have always been shortcomings with these products. As the monikers indicate, the most prevalent drawback of these products is that they are essentially paper saturated with asphalt. The organic paper core of these products is sensitive to changes in humidity and tears easily. Because the paper core isn’t 100 percent saturated, the paper can still absorb moisture, which can cause waviness when installed on the roof. Generally, the heavier the paper core, the more waviness potential. The other major drawback of these products is their propensity to tear easily. Tearing is a concern especially where it occurs around fasteners when the product is enduring foot traffic during roof covering installation. Tearing is also a major concern when it comes to the ability of the underlayment to remain in place during a high wind event, especially if the primary roof covering has blown off. 

The above concerns were the primary drivers for the development of synthetic underlayments. Synthetic underlayments are designed to provide superior strength: resistance against both tensile (pulling) and tearing. However, the test standards for these products just hadn’t caught up to product development – until now. Read More

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