The ground floor. the main enemy of outdoor storage is weather. while items stored under a deck are shaded from heat, moisture is still a major issue.. 3 ways to create waterproof dry space under a deck . by michael chotiner. april 11, 2016. in this article: deck membranes whether you use gutters, flanges or an under-deck ceiling, creating additional patio or storage space under your deck can add to your enjoyment and to the functionality of your home.. How to build a storage area under a deck | today's homeowner. find out how to enclose the space under your deck and keep the rain out so you can use it for storage.[...online service] 3 ways to create waterproof dry space under a deck | hometips. recover useful storage or utility space beneath a deck by utilizing a deck or an under-deck.