What is the purpose of roof underlayment?

The primary purpose of roof underlayment is to provide extra protection against moisture and leaks. It serves as a critical barrier placed between the roof deck and the roofing materials, such as shingles or tiles. Underlayment helps to prevent water infiltration that can occur due to factors like ice damming or wind-driven rain.

In addition to moisture protection, underlayment can also provide additional benefits, such as reducing the risk of wind damage to the roofing materials and assisting in managing condensation that may accumulate beneath the roof surface. This protective aspect plays a significant role in extending the life of the roofing system and ensuring overall structural integrity.

The other choices focus on roles that underlayment does not typically fulfill. For instance, it is not intended as a decorative layer or the primary insulation layer, nor does it primarily serve to secure roofing materials. While some underlayments may have features that enhance the anchoring of roofing materials, their foremost function remains the prevention of moisture intrusion.