An asphalt roofing felt paper is a vapor barrier underlayment made of a specially formulated organic sheet, which has been fully saturated with waterproofing asphalt and fiberglass. This product is flexible and impervious to water penetration but will allow water vapor to pass through at a restricted rate. Preconditioned to help it lay flat and remain stable after installation on a roof deck.
Asphalt felt is designed to be used as an all- purpose protective water barrier sheet in construction projects. Can be installed as a temporary roof cover during house construction and then serve as a permanent shingle underlayment after shingles are installed. As a shingle underlayment, it functions to restrict any vapor movement from the wood deck and attic to the underside of the shingles thus preventing condensation and as a barrier to wind-driven moisture which may get pass the shingle roofing