CertainTeed Underlayments come in a few different styles including, high temperature waterproofing vapor barrier, synthetic water-resistant (reinforced with gauze) and Sand WinterGuard. The CertainTeed high temperature waterproofing vapor barrier underlayments like the WinterGuard HT waterproofing underlayment can withstand temperatures of up to 250°F under metal roofs.The Certainteed synthetic underlayments are based on a tough woven polyolefin reinforcement (this reinforcement is laminated between layers of specially formulated UV-stabilized polymer films). CertainTeed also has a WinterGuard Sand (Granular) Underlayment that is designed for use as a waterproofing barrier on roof decks underneath shingle, slate and tile roofs.