Asphalt-Saturated Felt Underlayment: What You Need to Know

Roof underlayment can be made of asphalt-saturated felt, rubberized asphalt or non-bitumen synthetic. Asphalt-saturated felt is perhaps the most popular choice. It is one of the most common underlayments used by residential roofers and can consist of either an organic or fiberglass substrate. Of the two, organic, having a cellulose base, is much more common.

While this type of underlayment is water-resistant, it is not altogether waterproof. Here’s a closer look at its features, its installation process and its potential drawbacks.

The Installation Process

With low-slope roofs, such as those from 2:12 up to 4:12, roofers overlap felt courses by at least 19 inches. This doubles the layer of underlayment across the entire roof. In steeper roofs, however, the upper courses of underlayment should overlap the lower ones by 2 inches. Finally, in high-wind areas, roofers use plastic windstrips or cap nails to prevent tearing. Plastic caps resist wind and prevent leakage through the holes made by staples.

Potential Problems

Although asphalt-saturated felt is highly regarded in the industry, it isn’t without its faults and may fail due to the following reasons.

Poor Quality

Felt underlayment may fail because it does not live up to ASTM standards, resulting in unexpected roof repairs. These products absorb water faster and fail sooner. Wrinkling due to water absorption may show through thinner asphalt shingles. The roof deck can absorb water from the felt and result in expansion and contraction. It’s not easy to tell simply by looking whether a product complies with any standards. Premature failure or distortion is a telltale sign of substandard underlayment.

Loss of Volatiles and UV Exposure

Volatile compounds in the asphalt will dissipate, causing it to absorb moisture. It happens faster when exposed to heat from warm climate or poor ventilation. When felt is over-exposed to sunlight, ultraviolet (UV) radiation will speed up its deterioration.

Why settle for so-so roofing contractors when you can work with the best that the area has to offer? New View Roofing is here to provide you with superior underlayment for your roofing system. We serve homeowners in Little Elm, TX, and other nearby areas. Call us at (469) 232-7220 for a consultation.