Best 25+ Under decks ideas on Pinterest | Underneath deck ideas ...under-Deck Roof. under Deck CeilingPatio Ceiling IdeasCheap Ceiling IdeasDrop Ceiling BasementGarage Ceiling StoragePorch StorageBasement StorageStorage AreaDeck Patio. Drain away from house with slope, neat! Screw the fiberglass panels that form the under-deck roof to the purlins. This will be great for a shed to stay dry under the deck.