Roof underlayment materials provide the final surface on which shingles are attached. The most common type is roofing felt (sometimes called tar paper). It is often made of fiberglass “paper” impregnated with asphalt. This felt is available in #15 and #30 weights with the thicker paper, 30 lb paper being slightly more durable. These products must be fire, wind, and puncture resistant to meet current building codes.

Tar Paper Installation

Tar paper isn’t designed to act as a replacement for shingles. It is intended to make your roof less susceptible to moisture penetration. Felt is applied over the roof decking and may be layered over an additional water barrier such as flashing tape. Roofing felt is a very inexpensive material but not as durable as some of the newer products on the market. It must be overlapped properly during installation to prevent water from seeping between the layers. Extensive smoothing is often required to prevent wrinkling.

Thermoplastic polyolefin (TPO) is a membranous, synthetic roofing underlayment. It is less prone to leaking and tearing than traditional tar paper. One major advantage is the breathability of the material. Instead of trapping moisture in the attic, it permits water vapor to escape. This minimizes the risk of mold growing under the roofing material. TPO is generally available in wider widths that reduce the number of total seams that must be overlapped. This type of product is sometimes advertised as providing wrinkle-free installation.

Specialty felts are available for extreme climates. Some are designed to be self-adhesive and are thick enough to withstand ice as well as rain. They won’t allow water through – even around nail holes. These barriers are laid down first with a layer of traditional tar paper or synthetic membrane on top. With all of these materials, proper installation provides the greatest protection and longevity for your roof.

Related posts:

1. Roof Fire Ratings
2. Roof Flashing Maintenance & Repair
3. 5 Things That Can Damage Your Roof
4. Cedar Shake Roof Considerations
5. Coping With A Leaky Roof

Tags: Roofing

This entry was posted on Saturday, February 20th, 2010 at 6:41 am and is filed under Roofing. You can follow any responses to this entry through the RSS 2.0 feed. Both comments and pings are currently closed.