CertainTeed’s DiamondDeck® High Performance Synthetic Underlayment is manufactured to provide best-in-class performance in terms of both weather protection and contractor safety.
DiamondDeck is a synthetic, scrim-reinforced, water-resistant underlayment that can be used beneath shingle, shake, metal or slate roofing. It has exceptional dimensional stability compared to standard felt underlayment.
Felt underlayment can wrinkle when it becomes wet and “telegraph” those wrinkles through to the shingles applied over it. DiamondDeck eliminates this problem and its special top surface treatment provides excellent slip resistance, even when wet.