Layfast SBS is an SBS modified asphalt underlayment for use under tile, shingle and metal. The addition of SBS rubber to asphalt gives layfast an elastomeric property, which is not available in felt. Layfast SBS also exceeds ASTM D226 and is approved by the ICC. Available in three weights - 35, 43 and 70 pounds per square to meet a variety of budget conditions. For more information, visit