Underlayment is an essential part of any roofing system and there are a variety of reasons for this. First, a good underlayment preserves the lifespan of a roof by serving as a barrier between the top layer of roofing material and the roof deck’s substrate. As such, a good underlayment helps keep tar in shingles and other roofing materials from soaking into the wood beneath the underlayment.
Roofing felt also serves as a secondary moisture barrier in existing roofs as well as a temporary moisture barrier while a new roof is being installed. Should damage occur to the roof after installation, felt acts to help prevent moisture damage to the roof deck.
