What is the purpose of underlayment in roofing?

The purpose of underlayment in roofing is primarily to serve as a secondary weather protection layer. Underlayment is placed directly on the roof deck to provide an additional barrier against water infiltration and wind-driven rain. It acts as a shield against moisture that might penetrate through the primary roofing material, thus helping to prevent leaks and protect the structural integrity of the roof. This layer is essential, especially in areas prone to heavy rain or snow, as it adds an extra level of defense against potential water damage.

While other roofing components like shingles or tiles contribute to the overall weatherproofing of a roof, the underlayment plays a vital role in enhancing this protection. It is important to differentiate this functionality from other aspects of roofing, such as providing structural support, aesthetic enhancement, or acting as the primary roofing material, which are not the main purposes of underlayment.