Grain will need to be dried to acceptable storage levels. You will need to be able to keep the grain dry. Floors of existing buildings can be a source for moisture that will spoil grain. A vapor barrier should be used to stop the flow of moisture into the grain from the floor. Floors should also be graded to insure there are no low spots or areas where water can drain onto the floor.
Grain also needs to be protected from precipitation.
Walls of buildings should be re-inforced to hold the pressure exerted by stored grain. Portable bulkheads or grain bin rings can be installed inside buildings. You should provide a means for aerating the grain if it will be stored for more than a month. The air should be distributed through the grain as evenly as possible. For assistance on design of a system, contact your local extension Ag.