Three basic types of roofing underlayment include asphalt-saturated felt, rubberized asphalt and non-bitumen synthetic underlayment. Asphalt-saturated felt paper is a common underlayment for residential roofs with steep slopes.
Felt underlayment is often made from organic or fiberglass substrate and offers significant water resistance without being completely waterproof. Rubberized asphalt is self-sealing, making installation a simpler procedure, and manufacturers commonly design rubberized asphalt to be heat-resistant.
Roofing contractors choose non-bitumen synthetic underlayment when they wish to enjoy the strength and elasticity that asphalt-based materials don't provide. Professionals in the construction and roofing industries often use the term "polymer-modified bitumen materials" to refer to any synthetic roofing material that doesn't contain asphalt.