Underlayment is an important part of a roofing system; it affects how long your new roof will last, how it looks, and how well it protects your home from leaks.
Another factor that contributes to how your roof looks and how well it protects your home is the quality of the underlayment materials used, and whether it is properly installed.
Underlayment is a layer of material applied directly over roof decking boards before a shingled roof is installed. Several types of underlayment are available. In years past, asphalt-saturated paper (tar paper) was commonly used. Today rubberized asphalt, roofing felt, synthetic underlayment and even organic underlayment are available.
The purpose of underlayment is to create a water barrier that protects roof decking boards from moisture damage. It also provides a smooth, uniform surface for shingle application, and may help prevent penetration of heat and sound into the home. Rubberized or anti-skid underlayment also creates safer working conditions for roofing contractors.
Felt and Synthetic are the two most common types of underlayment used today. Felt products may be reinforced with fiberglass, and synthetic underlayment may be made of fiberglass, polyethylene, polypropylene or polyester. Both products come in a range of qualities and may come with features that minimize stretching, reduce tears, inhibit mold or add slip-resistance.
Synthetic underlayment costs more than felt, but is considered to be a high performance product with distinct advantages. It is lighter weight than felt and therefore much easier to work with, and it can be up to 600 times more tear resistant. This means it provides better leak protection, because it is less likely to tear around nails or from being walked on during the installation process.
All of the major roofing manufacturers provide complete roofing systems that include their recommended underlayment products. Generally, the use of the manufacturer’s specified underlayment is required to validate the full roof warranty.