The answer to 'types of underlayment' is that there are several common types of roof underlayment used in residential roofing. The most common types are asphalt-saturated felt paper, synthetic underlayment, and self-adhered membrane underlayment.
Asphalt-saturated felt paper is a traditional and affordable underlayment option. It provides a basic layer of protection between the roof deck and the shingles. Synthetic underlayment is a more modern alternative that is often made of polyolefin or other plastic materials. Synthetic underlayment is more durable, tear-resistant, and water-resistant than traditional felt paper. Self-adhered membrane underlayment, also called ice and water shield, is a self-sealing underlayment that provides extra protection in vulnerable areas like roof eaves, valleys, and around roof penetrations.