CertainTeed Water System

The Undershield water diversion system sends water that seeps through boards to a gutter at the deck’s edge, protecting the area underneath from water intrusion, according to the manufacturer. The clip-and-grid system uses stainless steel hardware to secure its 6-inch-wide, 16-foot-long vinyl panels to the deck’s joists. Panels and fascia come in white, gray, and beige. CertainTeed.