A heavy-weight asphalt roofing felt made of a specially formulated organic sheet which has been fully saturated with waterproofing asphalt. This is pre-conditioned to lay flat and remain stable during and after installation.This underlayment asphalt felt is designed to be used as an all-purpose protective waterproof 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 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 past the shingle. Can also act as temporary protection if shingle blow-off occurs. May also be used as a waterproof breather sheet on side-walls beneath outer finish .