Roof underlayment is a protective layer installed directly on top of roof decking and beneath the primary roofing material such as shingles or metal panels. It acts as a secondary waterproofing barrier.
The main function of underlayment is to provide temporary and backup protection against water infiltration during installation and throughout the roof’s lifespan. If the outer roofing layer is damaged or compromised, the underlayment helps prevent leaks.
There are several types of underlayment, including asphalt-saturated felt, synthetic underlayment, and rubberized asphalt membranes. Synthetic options are increasingly popular due to their durability, tear resistance, and moisture protection.
Underlayment also provides an additional layer of insulation and can improve fire resistance depending on the material type.
Proper installation is critical, as gaps, wrinkles, or improper overlaps can reduce its effectiveness. It is especially important in areas prone to heavy rain, snow, or ice dams.
