What material do roofers typically apply to the roof before nailing down shingles?

Roofers typically apply asphalt-saturated felt to the roof before nailing down shingles because it serves as an underlayment that provides an additional layer of waterproofing. This material helps to protect the roof deck from moisture intrusion, particularly during installation or if any leaks occur through the shingles. Asphalt-saturated felt is designed to be durable and helps prevent water from seeping into the roofing structure beneath the shingles.

Using this underlayment is essential for ensuring the longevity of the roof and enhancing its performance against adverse weather conditions. The use of asphalt-saturated felt also aids in reducing the risk of mold and decay, contributing to the overall integrity of the roofing system. Other materials, such as tar paper, may serve similar functions but are often less commonly used compared to asphalt-saturated felt, which offers superior protection and compliance with modern roofing practices.