UnderDeck. The Original attaches to the underside of elevated second-story decks turning the area below into a clean, dry, and bright space. Our under deck system can This feature is not available right now. Please try again later. The principle here is simple: the panels are installed on a slight grade which allows water from the top deck to fall through and drain off. Since we didn’t want This is an inexpensive way to put a ceiling under your deck. The actual ceiling systems are very expensive. It looks great and costs much less than the Shop under deck ceiling systems in the decking & porches section of Lowes.com. Find quality under deck ceiling systems online or in store.