Under deck is fairly new and catching on fast. It consists of a metal covering on the underside of a wood deck that is at least 1 story off grade. The metal channels water to the perimeter of the deck, thus making the space underneath usable for storage and/or patio space. Although this system is not guaranteed to be 100% watertight they usually are. The little leakage that can occur is in the winter when the area is generally used for storage. Most of the time, after the water is channeled to the perimeter, a gutter is installed so the water is collected and deposited away from the activity area. Pre-finished steel is the exclusive choice of material for this system, as it gives you the choice of 30 colors.